Zed Body Progress

With the weather shifting warm to cold to warm again, Zed (the 1979 280ZX) work has been a little bit on-again / off-again. With the weather returning to hot for what looks like the Summer, I shifted efforts back to Zed from the other projects (you've seen the posts)... well, until this past weekend when everything came to a complete stop due to the record-setting high temps (over 45*C / 113*F). Today's post focuses on Zed's body work again, solving for the missing rear bumper and getting after some priming. Again.

Bumpity Bump

A lingering question for Zed was how to solve for the rear bumper. The original was a rusted out mess, and donorZed was about as bad. I was considering how to construct something one-off custom, but decided that an off-the-shelf fiberglass kit was a better looking, and fastest-to-implement approach. Rather than just do the rear, I got a full kit, so the front-to-back is consistent. Of course, this will delay the paint a little bit, as I have more body panels to solve for. Plus there is the added delay introduced by shipping. Ultimately, Zed will look better, so it's worth it. The kit I ordered looks like the one pictured on the side here, without the big wing on the back. That's not my style, but everyone gets an opinion. Later, I will add louvers to the rear window since that window lets in a ton of heat in the summertime if left uncovered.

In order for the rear fiberglass to mount, I needed the rear bumper bar that sits inside the big rubber ugly. I reconnected with the local Z parts-hoarding-guy to whom we sold donorZed and bought a rear bumper bar, and mounts... for about 1/2 what we sold the entire donorZed to him for. Funny how this all works. Perhaps, in retrospect, I might have saved the original rubber bumper support bar and mounts. Anyway, next was clearing the rust off the bumper mounts, and getting them ready for action. I used multiple passes with Naval Jelly followed by a coat of Eastwood Rust Encapsulator and then a coat of rattle can primer. I will shoot these with the hinges and other tiny bits that we want the color of the finished body.

Following that, I removed the front bumper support (4 16mm bolts each side) and the bumper from the supports (4 14mm nuts each side). Next, I wanted to remove the rubber ugly wrapped around the bar so we were ready for when the fiberglass kit arrives. The Phillips screws that hold the ugly cover on, however, were rust-locked in place. Multiple passes with the Kroil didn't allow them to budge. So, I had to grind them off. It is interesting how much rust was on the bumpers and how little the rest of the car had. Those front bumper mounts had virtually no surface rust on them while the bumper itself had been impacted. These mounts will also get the color spray with the other bits I mentioned above.

Prime Time

Last, I finished enough of the Bondo cycle to feel that I could lay another round of hi-build primer. The Bondo-cycle took an awfully long time, and I got far too into it. I imagine I still missed a bunch of things and it still will not look as good as a real pro paint job, but at some point you just have to stop dicking with it and go. Otherwise, you will never get to enjoy the fruit of your labor. It's just labor. I am enjoying the heck out of bodywork though, which I kind of surprising. My first round of high-build primer was both too light and mostly sanded off so if you are concerned that there will be this huge stack of paint layers, rest assured, that is not happening. I did have to wait for the weather to get warm and dry enough, though.

Once the weather turned warm again, I acted like the primer had not happened before: restoring the masking, vacuuming and blowing air, cleaning the snot out of it, etc. so it was ready to get primed. Then, I laid the body panels out under the car-port cover again and repeated the multi-passes of primer, just like I did last Fall (See Zed Prime), with a few differences. My set-up this time did not include the in-line line drier nor extra pressure regulator. I had not gotten another disposable line-drier, and without it, I could not attach the regulator. So, I set up my pressure with test fan blows on one of the fenders instead. Total Roadkill. I figured I could reduce the moisture if I kept the air compressor tank warm, so I moved it into the sun. Since the air around here is super-dry right now (humidity below 30%), there isn't much moisture in the air to get compressed into the air line anyway. This may sound sketch, but the primer landed fine.

As to shooting, I did a light first coat to give subsequent coats something to adhere to, while also avoiding runs or sags. The sunlight was so bright, it was hard to really see the fan, since the color of the primer was the same as the target panel most of the time. Similar to the 1st shoot, I did not meaningfully stop between coats 1 and 2: fill the cup, shoot the cup, repeat. Why? Because, by the time I got all the way to the end of the light coat, the place where I had started had sat for longer than the minimal flash-dry period, and it was warm enough to dry fairly quickly. The surfaces were tacky when I went around for my heavy pass, which, I felt, was just right.

The 2mm tipped gun got clogged about halfway through my 2nd coat. As I attempted to unclog it, I lost about half of a shooting-cup (or about an actual imperial cup) of paint: it turned to Jello. I think I mis-measured the concentration of hardener. Could it have been from the lack of an air-drier? I dunno. Undaunted, I grabbed another gun which had not been drilled out to 2mm; it was a 1.8mm tip. I did not clean it first, I just blew a few seconds of primer through it and got back to the job. Yes, that was lazy and yes it could have allowed for some shipping oil/crud into the primer. I considered all this and used the first little bit of shooting to second-coat the nose section that will be mostly hidden from view (under fenders, radiator support, eg). More Roadkill; maybe that show is a bad influence on me. Anyway, I finished the pieces I had not gotten with a 2nd coat after I shot some hidden areas. I found that the 1.8 tip flowed better, gave a smoother finish and had a more predictable fan than the 2mm drilled tip. So, I take from that either (a) I drilled the tip wrong or (b) my 21gal compressor, pressure set up, gun and material were all better suited as a unit to the 1.8mm tip. I'm not sure how you drill wrong, so I think the difference is really tied to my compressor, and it's ability to keep up with the air-pressure demand of the 2mm tip. Regardless, I will be shooting this high-build with the 1.8 tip on a very warm / hot day from now on.

Reviewing the Prime

None of these changes, including the especially Roadkill-inspired ones, appear to have made much of a negative impact on the primed surface. Quite the contrary, actually. I started setting up the first gun at 10 and finished spraying by 2. I took an hour to clean up work area and the second gun (first gun went into the garbage) as I let the panels sit for the rest of the afternoon. Late the following afternoon, after the panels had sat in unseasonably warm temps (30*C+ or 85*F+) most of the day, I did some test sanding on the mostly-hidden areas with some 320 grit paper. The primer powdered smooth very quickly. If this is any indication, then this priming session was much better than the first. Perhaps this high-build poly-primer is more temperature sensitive than the Eastwood folks indicated on their site: warmer drier days are much better. The first time around (when it got into the lower 50's*F/11*C overnight after shooting), there was meaningful stippling on the surface. This time, when the overnight temps barely got below 70*F, the surface is much less dimpled. And, it sands smooth much more easily; like, a few passes with 320 and it's smooth. Last Fall, I tried pre-warming the panels inside my garage but that had no effect: the shell which sat outside the whole time had the same little dots peppering the surface. I think the real difference was the long warm days both the day of and after shooting.

Learnings

My big take-aways from the shooting the hi-build poly-primer from Eastwood: use a 1.8 tip and an in-line drier on a warm-to-hot day when the overnight temp will not fall below 18*C or 65*F for best results. Do a quick-coat first for the next heavier coat(s) to adhere to. Last, it is a good idea to have an extra gun as an emergency fall back in case you mess up the hardener concentration and jack up your gun in the middle of your spray-sesh.

Go Forward

Next, I will be sanding the rest of the body panels. Then, once it arrives, I will be handling the body kit. At some point, there will be paint, but I may shoot a urethane primer/sealer first (once Eastwood has it in stock and ships it to me). And, of course, the body kit will probably need some tweaks and then priming. I sincerely hope I can get it all done before the weather prevents it. While the Fall rainy season is a distance away, we cannot guess whether we will be revisited by toxic smoke again, scrapping late-Summer plans. For that matter, we are having triple-digit heat waves (40*C+) that are keeping me penned inside as effectively as the smoke did last summer. 

I expect that if I have to wait too long for the body kit, I will set up and shoot the parts that will not be impacted (like the underside of the hood, the hinges, the bumper mounts, etc) so I can make some headway and save myself some shooting time later while also getting a better feel for the equipment and material. Some of this stuff may not be terribly post-able, but I will try to at least put a little message here about the work.

Thanks, as always, for following along-

MGB - Brake Booster Replacement

In my last post about Oliver, the 1978 MGB, I mentioned that the brake booster was the cause of a vacuum leak in the engine. This vacuum leak was causing cylinder #1 to run very lean compared to the others. Fortunately, Oliver has not seen much road time, so the engine should be fine. Regardless, today, I cover the fun of removing and then installing a replacement brake booster.

I would like to note that the body work on Zed came to a full stop when the Oregon weather predictably shifted back to cold-wet. For those who don't live here, we experience a wonderful donut-hole of beautiful weather in April/May smack in the middle of the cold-wet. The cold-wet returns for the month of June, usually lasting until Independence Day. So, I entertained myself with other projects, like this, while we waited for the weather to change back. After yesterday's high temps, I suspect the cold-wet is over until October.

Booster in an MGB

We start with where the booster lives in the small engine compartment of the MGB. The brake master cylinder, the clutch master cylinder and the brake booster all live together, attached to one another through the "pedal box": a rectangular steel box just in front of the firewall on the driver side. Closest to the rear is the clutch master cylinder. It is bolted to the back of the box with a lever extending into the box and attaching to the clutch pedal with a pin that is held in with a cotter pin. Attached to the front of the pedal box is the brake booster, with 4 1/2" nuts. This has a lever passing rearward, attaching to the brake pedal with a similar pin-with-a-pin design. To the front of the booster, the master cylinder is attached (2 nuts either 7/16" or 1/2"). Into the master cylinder a rod is passed from the brake booster.

You can imagine the brake action then: pedal is depressed which leverages against the clevis pin to press the lever into the brake booster. The brake booster converts some engine vacuum into more braking force which is then applied through the rod to the master cylinder.

Booster OUT OF an MGB

booster out

The Bentley manual has a step-by-step instruction for removing the brake booster, but I found the instructions to fall down. It started with removing the cover on the pedal box. I agree with that. It then described removing the clips for the brake lines leading to the master cylinder within the engine compartment. I agree with that. Then, it instructed to remove the bolts holding the brake master cylinder to the front of the booster. I also agree with that. At this point, the brake master cylinder can be slid forward off the booster-rod. By doing it this way, no air is introduced into the brake system. I likey.

Then, the instructions said to remove the cotter pin holding the clevis pin for the brake pedal to the leaver on the brake booster. This is not possible for anyone with adult male (and probably female) fingers for width and no one with child fingers for how deep you need to go. The gap between the side of the box and the partition which runs front-to-rear is not wide enough for fingers. I tried long needle nose pliers, but I concluded that even if I got the cotter pin free, and got the clevis pin off, I would not be able to re-install this way. So, I started my own path from here.

My plan was to remove the pedal box with the brake booster still attached and remove the booster from the pedal on my bench. Unlike the brake cotter pin, the partition is much wider on the clutch side, so my average-thickness fingers were able to remove both the cotter and clevis pins without too much difficulty. So, with the pedal disconnected, we remove the clutch master cylinder from the box by removing the 2 bolt/nut combinations that attach it from the rear.  Once removed, the clutch master  cylinder can be pushed rearwards out of the way. Next, we focus on the pedal pox. There are 2 bolts from the top, along the outer edge of the box nearest the centerline of the car. There are 3 bolts from inside the driver footwell going up. Last, there are 2 bolts from behind the dash running forward. Once all 7 bolts are out, the box is only held in place by gravity and the seal. Some light upward pressure on the brake booster and the unit pops free. Getting the unit out of the car took some wrestling, but I think this was more difficult because I could not see where the pedals were dangling. I found that by rotating the unit 90* clockwise helped the pedals to make it through the hole. had I read my old post about removing the pedal box (See MGB - Master Cylinders (Part 1)) or the post about the install afterwards (See MGB - Master Cylinders (Part 3)), I would have known to loosen the bolt fastening the clutch pedal so it dangled a little bit more. This would have made the removal much less of a muscle effort.

pedal box upside down on
workbench with old booster

Once the pedal box was out, it was a simple matter to remove the cotter pin and clevis pin between the brake pedal and the brake booster.... from the underside. I removed the remaining nuts on the brake booster, and started the install by performing the steps in the opposite order: attach the brake booster to the front of the pedal box. Thread the clevis pin through the lever and pedal, minding to include the washer before re-inserting the cotter pin.

Booster Back In MGB

With the unit in the same relative state of assembly as it was in when it was removed, I returned to Oliver to install it. I approached the install in the same manner as it was removed: rotated 90* so the booster was pointing across the engine. The pedals didn't fit, but with some rotating of the box and squeezing the pedals together, I could get them to fall through. Then, I wiggled and rotated the box, checking for cables wires and tubes from getting underneath until it settled in place. I decided that I would do the hardest first, so I did the clutch pedal/master first. I bolted the clutch master cylinder to the rear, after wiggling it around to fit, setting the lever alongside the clutch pedal. Then, I attached the pedal with the clevis pin and cotter pin. I found there was more play that I expected at this joint point, and concluded that I got the clevis pins backwards between the brake and clutch. Food for thought if you are doing this: the longer clevis pin is for the brake.

new booster in

With the clutch master cylinder tied in, I added the brake master cylinder to the front. This is much easier to get to. Once fitted, I started fitting the pedal box to the body. Because of the brake and clutch hard-lines, the pedal box is reluctant to move. I found that putting the 2 bolts through from the dash forward into the rear-most part of the pedal box allowed me to move the box into position. Once the bolt holes along the inside edge (2 of them, one 1/2" one 7/16") aligned, I set those 2 through. Last, I got back on my back inside the driver footwell and sent the last 3 7/16" bolts through the outer edge of the pedal box.

Brake Booster Hose

With the new booster on the pedal box and the pedal box in the car, all that remained was connecting the vacuum hose. I had oriented the booster upside down from the original so the vacuum nipple is on top, rather than below. I did this because of the significant heat source below the booster (exhaust) that is less present above. Also, the hose is much shorter and straighter from intake manifold bung to brake booster nipple. Wanting to avoid any possible issues with the original one-way valve on the intake manifold, I replaced it as well.

Re-Tune and Jetting

Because the old booster was creating a vacuum problem, I re-did the ColorTune tuning steps. Similar to the first time, I tuned using cylinders 1 and 3 but achieved a nice blue in both banks this time. I did swap out the idle jets (50F9 jets), but in order to find blue, I had the idle mixture screws further out than 2 full turns. I will drive Oliver around a little bit, but I think I may need to go up to 55F9 jets if the instructions in the SK Racing manual are to be followed. I noticed that the SK Racing product page describes the "pilot jet" in the carb set-ups they are selling today as 55. Assuming this is the idle fuel size, that's more support for trying 55F9 idle jets.

Since these SK Racing carbs are so similar to the side-draft Weber, here's another tuning link I found specifically for Weber. Notice how that article indicates the starting spot for the idle mixture screw is 2.5 turns out? That is about where mine are now. Curious. One last link, again on the much more plentiful Weber DCOE, but this time about some recommended jet sizes. It recommends the 50F9 idle jets for a late B like I just put in, so honestly, at this point, it will come down to a road test.

under the jet cover plate

Swapping out jets in this carb is seriously one of the easiest things I think I have ever done on a car. There is a cover plate on the top of the carb which is held in place with a slotted bolt. Once the cover is removed, the 4 jets (one idle per side and one main per side) are held in with slotted jet holders. The idle jets are the ones further from the engine / closer to the air filter. The holder threads out, and the jet is held in the holder basically with friction. The old jet slides out, the new jet pops in and you thread everything back together again.

The engine tune did not meaningfully change after the re-jet, so I concluded that the air-fuel mixture from the old jet was virtually the same. So either I removed a pair of 50F9 jets only to put in new ones or the old ones were a similar enough combination that they provided the same air-fuel at idle. At least I know what they are now.

All that is left is a drive... but wait! I didn't hook up the brake light switch. Well, I did, and after a few days of head-scratching trying to get the lights to illuminate, I realized that I had plugged it in wrong. The source 12V arrives in a dual plug, and the signal to the brakes departs through a single plug. I had thought the single plug was from the old carb-preheater, so I had failed to send either side of the switch to the brakes. Instead, I simply wired both sides of the switch to the 12V supply. Hahaha. Simple fix. Once the cars were shuffled so Oliver could get out past the herd, I did a longer test-loop. It did not take long to get the engine to normal operating temperature and he ran great. There was a slight stumble (bog) from dead stop, indicating that he was still a little lean. So, once back in the garage, I turned the idle screws about 1/8 a turn more rich. When I rev'd him from idle, I could not note a bog so I figure he is fairly close to tuned now. More road testing will confirm, and I expect I will fiddle with these screws as weather and altitude factor.

Thanks, as always, for following along-

Nemo Re-Assembled

I think this will be a quick post. In my last, rather lengthy, post about Nemo, I described the effort to get him running again. Today, I cover the electrical mop-up and the other little bits to get Nemo ready for regular use... by someone. While this is barely post-worthy, the wiring fix did take me a few hours, so in a way this is just documenting how I spent a Saturday. Besides, the weather has turned too cold to spray primer or paint, so Zed sits waiting.

Car-Toys Vent

I will start with a predictable slam on the hacks at Car Toys. Recall that when they replaced Nemo's stereo, they were directly asked/told not to cut up the wiring, rather to use a pigtail. With a generic response of along the lines of "we'll do it right" wink/finger-point, they did exactly what no one wants a radio installer to do: cut wires off of a harness plug and then direct-wire a new stereo into those bare wires. So, I give them a "that's not right" glower/different-finger-gesture. All-told, they cut the 8 speaker wires, switched and steady power, ground, power antennae and illumination. The part I don't understand is why they do not have a cache of pigtails for common cars. All VW's and Audi's from, like, the mid-80's thru modern cars use the same 2 8-pin female plugs... one 8-pin plug for the speakers and one 8-pin plug for the power, illumination, etc. The corresponding male pigtails run for, like $10US on eBay, and since they plug right in, the install is faster, while also cleaner: at a workbench, the custom pigtail for the new stereo can be wired into the Audi/VW standard male pigtails. Then, you take the stereo head-unit and the cable to the car, plug in each end and you're done. Cleaner, easier, faster. Instead, Car Toys does it lazier, longer, stupider and uglier... and much harder to undo.

Stereo Wiring Un-Hack

With the center console fully opened up, I had great access to the great wire hack. I started with the speaker wires, mostly because bits of the CarToys wire-extensions (1 each purple, grey and green) were still attached to a few wires post-theft, so I could tell what they used to be used for. Once those 8 wires were sorted, the remaining wires were much easier to isolate. The only difficult pair were the switched and steady power sources, because both were plain red wires. A simple voltage test (one had 12V and one didn't while at rest) resolved that. Yes, there was a hot wire bouncing around back there. Once the pigtails were wired up, I zip tied the wires into a cable on either side of the wire butt-joints so any gentle pulling would not cause a wire joint to separate.

Climate Control and Console Re-Assembly

With the loose wires sorted, the center console already looked 100% better. I continued the re-assembly by plugging in the climate control unit. While this has 4 plugs, they are each slightly different sizes so they can only go in one way. Once plugged in, I slid the unit into place and threaded in the Torx bolts to hold it in. Then, the console cover can snap into place. 2 8mm Allen head screws later, the center console is together again. I take satisfaction in seeing the stereo plug through the hole where a stereo should be. I may pick up a cheapy clearance stereo from Crutchfield to completely close the loop... and that hole.

Kick Panel and Re-Lo

All that remained was putting the lower dash panel back on. This panel is held in place by 3 screws: one at the bottom of the fuse box frame and 2 in front of each of the driver's knees. The fuse box frame screw is easy to get to and easy to manage. The 2 in front of the driver's knees, however, require some gravity-defying. I do not know what kind of fastener was originally used; Nemo has slotted bolts. These bolts need to be balanced on the end of the driver and then tilted over about 30* to find the hole in the panel, and then the matching hole in the dash. While this is not hard, it can be frustrating. Once bolted tight, the holes are covered with small plastic bits that snap into place.

Just like that, an interior that looked like it was at a junk yard is re-assembled and looking sharp again. I juggled cars at this point, moving Nemo into a more remote spot, out from under the carport. As before, he started right up like he hadn't been un-start-able for weeks. The juggle created the space needed to get Oliver out for some Summer driving. I did discover, however, that Nemo's front passenger window I replaced also had the front window tracking mechanism damaged when the window was smashed in. So, the window does not go up and down anymore. I will need to hit the junk yard again, to source a replacement window track thing. Neat. I do like going to the junk yard, though, so maybe I'll find some other stuff we need while I'm there. In the meantime, Nemo's air conditioning blows nice and cold, so a stuck window doesn't mean discomfort.

That's it for today. Thanks, as always, for following along-

MGB - Finding Vacuum Leak

Following my last post about Oliver (the 1978 MGB) when I got his timing square, I knew I needed to get his carb tuned. Today's post covers those efforts. This continued in parallel with the body work on Zed (until the weather turned, when Zed work stopped). These spring days, when the sun doesn't go down until 9PM creates LOTS of play-on-cars time. Love it.

A-typical Carb

We start with the most basic learning: what kind of carb is this? When I bought this car, the prior owner had been executing some improvements. For the most part, I can't complain about any of them... except the hack-job on the exhaust. Honestly, he could have been just making do until he had the cabbage to do what I did. Anyway, one of the improvements was to eliminate the stock dual Skinner Union (SU) carbs and swap in a side-draft carb. This isn't your standard Weber DCOE, though. Instead, the prior owner went with a SK Racing carb. The SK Racing (now known as OER Racing) side draft carb was (according to Dog283) one of the best engineered side draft carbs built, just as carburetors were falling out of favor for the new computer-assisted fuel injection systems. Dog283 continued "(the SKRacing side draft) combine(s) the best of the the Mikuni Solex PHH, the Weber DCOE and the Dellorto DHLA". That's a fairly strong statement. Unfortunately, the implementation on Oliver had fallen out of tune, so our MGB was not getting the lofty results this statement describes.

We start with looking for, and ultimately finding, a shop manual for the SK Racing side draft carb. If you have one of these carbs and need a copy of this manual, I'll happily share it. Near the back of it are the set-up steps detailed in the image of the page on the right. Basically, set the idle speed screw so it is just barely touching the tang, thread the idle adjustment screws all the way in until they just barely seat and then rotate them back out 1 full turn. Start the engine and get it to normal operating temperature. Then, tune the adjustment screws first until the engine runs smoothly, then set the idle speed. I did that, but I still got sporadic backfires when I rev'd the engine. I was starting to think that all that ignition work was for nothing.

Exhaust Leak Checks

Before I started investing time in the carb, I figured it would be a good idea to see if there were any leaks in my exhaust which could account for the backfiring. There were. To test, I started by cleaning out my shop-vac (washed out with a hose) and grabbing a squirt bottle of soapy water. I thrust the exhaust end of my now-clean shop-vac up the tail pipe and turned it on. This created backpressure through the exhaust. The tail pipe was not completely blocked so lots of air rushed right back out, but there was enough pressure to execute my test. I started up front, in the engine compartment and shot soapy water on the mate-point between the header and the head. No bubbles. I then got under the car and hit every joint, and found some bubbles. I concluded that I created leaks when I added in the catalytic converter. I turned off the shop-vac, loosened the joints, slid the pipes apart and applied some copper exhaust gasket maker and then re-connected the pipes. I nutted them back down and re-checked with the shop-vac. Things looked fixed (no bubbles at all but one joint where there were very very few), so I moved on to tuning, expecting my backfire issues had been identified and resolved.

Gunson ColorTune

Back when I was doing the other work on Oliver, I kind of expected difficulty with getting the carb to adjust. So, before I finished getting the ignition installed, I ordered a Gunson ColorTune. These things are pretty neat, but not terribly useful, I suspect, for the computer-controlled fuel injected systems. The kit includes a looking-glass spark plug, a lead, a tube with a mirror and a brush. I only needed the glass spark plug and the lead. The looking-glass has a solid-center where the spark is produced, with a ring of glass around it. The glass ring is then encircled with threaded metal so it can be threaded into an engine. The tube with a mirror is for spark plug holes that are hard to see. To use the kit, you remove one spark plug and thread the looking-glass plug in it's place. You connect the spark plug lead to the end of the lead from the kit, which is threaded onto the glass plug. Then, you start the engine and look at the color of the combustion in the chamber through the glass. If the color is orange or red, your mixture is too rich. You want the color to be "Bunson blue" = the color of a Bunson burner, from, like science class. The images on the right, here, help lead you to a good tuning. Notice that light blue or white-ish is not on here. If you are in the white-zone (Airplane, the movie reference here), your tune is too lean.

I was unable to get cylinders 1 and 2 anything better than a very light blue even after adjusting the idle mixture out past 1-1/2 turns. Cylinders 3/4 did not do much better. Based on the manual, I believe the idle jets may be too small, so I ordered a pair of 50F9 jets ($7US each). If I am correct, the current idle jets are 45's and this change will allow idle-mixture within 1-1/2 turns of fully seated to sit in the Bunson-blue color.

Still, I kept going, wanting to get the tune as good as I could. While looking through the glass I increased the fuel mixture incrementally, but the misses and backfires persisted. I could see the backfiring through the glass in cylinder 1, and concluded there had to be a leak somewhere. I also figured that backfires within a cylinder that has a glass plug was probably not a good idea. I had already looked on the exhaust side for leaks, so that left the intake.

Intake Vacuum Leak Checks

There are not many places where a leak could appear in the intake: the mating point at the head, the mating point with the carb, the carb itself and the brake booster. With the engine running, I carefully sprayed some WD-40 onto the various mate points. If there had been a vacuum leak, the vapor would have been drawn into the engine and the RPM would have bumped in response. Spraying something flammable onto a hot engine is dangerous. I strongly urge you to keep a fire extinguisher handy if you do this. In my case, the engine did not change and nothing caught fire.

So, I shut everything off and considered the brake booster. I removed the hose from the check valve, which is threaded into the intake manifold heading to cylinders 1 and 2. I checked the vacuum of the brake booster through that hose with the MityVac. It would not hold vacuum. I removed the check valve and cleaned the valve and the intake manifold where they met. Then, I put some copper gasket maker on the threads of the check valve and threaded it back in. I figured if that was the leak, I just solved it. I jabbed the hose back onto the check valve and hose-clamped it tight. Then, I eliminated the brake booster by threading a bolt into the end of the hose which had previously been attached to the booster, and started the engine. Oliver ran great! I could rev him up and down without any backfires demonstrating that the brake booster was my vacuum leak.

check valve in foreground,
intake in background

I wanted to prove it for sure, so I hooked the booster hose back up to the brake booster and started the engine again. I rev'd the engine up and down... the back fired returned. I pinched the vacuum hose with a pair of pliers and I could hear the engine RPM's settle. Neat. Rev rev rev... no back fires. Remove the pliers, RPM increases... rev, rev, rev... backfires.

Fortunately, these brake boosters are being manufactured now. I didn't realize these were not available until recently, so as much as I would like to self-blame for not replacing the booster when I replaced the brake and clutch master cylinders, it wasn't available then and they are fairly expensive now (~$200US). As of today, they are not available through Moss yet. I had to go through another vendor (EnglishParts.com, they're lovely). I concluded that any carb tuning I had done would need to be redone once the brake booster swap was completed. 

That's it for today. I will install and post about the brake booster when it arrives from the MidWest. Thanks, as always, for following along-

Oh, Nemo

Today's post covers my challenges with Nemo's electrical and computer system simply trying to get him to start, or maybe a signal on the OBD-2 port. The car-work hours that I did not want to spend sanding on Zed, I spent doing this... until this took over. Yeah, I know. I could use another hobby.

No Start

Like so many issues with these old cars, our challenges with Nemo started with him not starting. His battery had been sitting on a trickle charger all winter, but I had left his hood cracked to make room for the alligator clips, so this ultimately was self-inflicted. Love those. But, the path we took to get there was interesting. Nemo is sitting under the fabric carport blocking a garage door. Behind that garage door sits Oliver, the 1978 MGB convertible, that I would very much like to be road testing and otherwise driving around. So, enter my motivation for moving Nemo. Insert key, turn ignition to "RUN". I see some familiar idiot lights, including the battery, oil and check-engine. Turn to "START" and he rev'd but would not start. I went around to the tailpipe and could not smell gas, so I start with the assumption that it is fuel delivery.

Before I did anything else, I considered what I experienced when I turned the key to "RUN". I did not hear the fuel pump cycle. I did not hear the radiator fans kick on. So, something is not getting the "RUN" signal. So, I pull out the UltraGauge and plug it into the OBD-2 port. I get a never-ending "scanning..." message. Well, that's not good. I double-checked the UltraGauge in Hapy, and the computer linked within a few seconds. Okay, we have trouble with Nemo's diagnostic system which could prevent a start or we have multiple things going on. With this car, the latter is probably true. First, I tried to isolate the OBD-2 issue, and kill many many hours doing so.

OBD-2 Issue Diagnosis: General

The early B5 versions of the A4 had some interesting 1 or 2 year only issues. One of the oddities around 1997, when Nemo was sold, was the engineers choice to integrate the stock stereo with the "K-line": the signal processing wiring between the computer, many components and the OBD-2 plug. In these late 90's cars, it is the K-line you are subscribing to, not the more modern "CAN BUS". Okay, cool. There are many modules plugged into the K-line, but they are all in parallel. the diagnosis theory goes that when you get no signal on the K-line it is because one of the modules is faulting out, grounding the K-line. Once you can identify and remove the faulty module, you will get a signal on the K-line. You will probably get a failure code for that module, but you will at least get a signal. So, away we go, trying to figure out what modules are even on the K-line, and then isolating them.

OBD-2 Issue Diagnosis: Radio

The stock radio wiring was unceremoniously cut to pieces by the idiots at Car Toys when they installed an aftermarket stereo. Based on the wiring diagrams I have found and the commentary on the interwebs, I am not sure this car actually had that K-line-in-the-stereo thing. I did check the wires for the right color combinations, and for wires that were the correct colors for the K-line. I was unable to find them. There are, however, many wires sticking out of the hole where the radio used to be... before it was ripped off in Eugene. I intend to re-integrate an original plug before I put all this back together, but that's another day. I moved on to the next possible culprit: the climate control system.

OBD-2 Issue Diagnosis: Climate Control

found in climate
computer

The climate control system in these cars is another little computer. In some models, it is held in place with a couple brass clips. In Nemo, I had to remove the center console cover plate / face and found 2 Phillips screws holding it in. Once threaded out, the unit removes through the front. I unplugged the unit and checked the OBD-2 for a signal. Nope. I did, however, find a soda/beer can pull tab inside it (picture on the right, here, laying on the carpet after I removed it from inside the climate control computer thing). So, that was interesting. Next.

OBD-2 Issue Diagnosis: ABS (Brakes)

The fine folks on the interwebs have found that the ABS sometimes causes K-Line problems. The way to identify if it is the problem is to disconnect the plug. The ABS unit is on the driver (left) side, next to the washer bottle. You simply pull up on the silver metal tab and the plug lifts out of the socket. I found a piece of electrical tape floating around in there. Another question-mark from the prior owner. Neat. I checked the OBD-2 for a signal. Nope. I shot the socket and the plug with DeOxit and left it disconnected for the rest of my tests. I figured I might as well leave it better than it was (DeOxit, not leaving it unplugged). Next!

OBD-2 Issue Diagnosis: Dash Cluster

Moving on, we consider the dash cluster. The entire thing is held in by 2 Torx-head screws from the front, hidden behind a cover plate just above the steering wheel. Pull the cover plate, remove the screws and it pops right out. I unplugged the various cable plugs and checked the OBD-2 again. Nope. Grr... Next!!

OBD-2 Issue Diagnosis: ECU

example A4 ECU 

It seems like every system on the engine that has more than one wire into it delivers some signal to the computer. So, this seemed like the next logical step. I figured if I could get a signal after unplugging the small plug on the ECU, I would have shown that the issue is in the engine compartment and I could put everything in the cabin back together again. If the issue remains, then it could be the ECU. So, I disconnected the small plug from the ECU and we still didn't have a K-line signal. Grr...

So, I plugged the ECU, ABS and the dash cluster back in, turned the key to RUN and heard the click-snap of some relays firing, but no fuel pump nor fan spin. I could not remember if I heard the relays before, but this changed my thinking. If at least some of the relays are firing, then the ECU is telling them to. If there is a Check Engine Light, then the ECU must be at least partially working. Perhaps the K-line / OBD-2 issue is completely unrelated and this is just a simple fuel supply issue. So.. new plan: get the fuel pump to fire.

Fuel Pump Test

As is so often the case in laboratory settings, the pre-work for the experiment is where all the time is taken. Such is the case here. I started by removing the plate covering the fuel pump. This sits behind the rear seat in the trunk on the passenger (right) side, and is held in place with 3 very short Phillips screws. Once the plate is removed, you can see the top of the fuel pump. There are 2 fuel lines, one supply and one return, and a single electric plug. I found that slightly wiggling the plug allowed it to pull off the pump. YMMV. Once removed, you will see 4 pins. 2 of them are for the fuel level and 2 are for the pump. I started my tests with basic resistance and continuity-to-ground. Things seemed fine, so I shifted focus to test-firing the pump by applying 12V to the pump.

This is where the experiment set up took some time relative to the actual test execution. I ran a pair of wires from near the battery (not hooked up) back to the fuel pump. At the battery, I taped 10A fuse to the "red" wire and alligator-clipped the other side of the blade to the positive battery post. I alligator-clipped the "black" wire to the negative post. Back at the fuel pump, I applied the red and black wires to the fuel pump and it fired right up. I held the wires there a few second to demonstrate that it would not just run for a second and die. So, we have a good pump, but the pump won't fire from a relay signal. So, next we check the voltage from the relay, after we put the experiment wiring away.

Fuel Pump Relay Test

A4 Fuel Pump Relay

Back up front, I took a red wire, stuck it into the voltage-supply pin in the wiring plug at the fuel pump and tossed the other end through the cabin, over the outer edge of the driver seat. My plan was to compare the voltage sent to the pump at the pump. Since the relay only pops for a second when you turn on the ignition, I had to have my test equipment near the ignition key. I stuck my black lead against the metal fuse box mount, held the red lead against the wire I tossed through and turned the ignition to "RUN". I got 5V. I checked other spots around the fuse box and got 13V, so I started thinking that the relay was bad, dropping the voltage from 12/13V to 5V which, of course, is not enough to run the pump. So, I swapped out the relay... and the fuel pump still would not run. Great. I concluded that the 5V I read was actually the base charge for the fuel level sender and not the supply for running the pump. 

So, I checked the voltage at the supply-side of the relay: 13V. I jumpered across the relay pins, and the pump fired up. So, we're back to the ECU is not sending a signal. Fearing it is the ECU, I went looking for any other reason. I recalled that when Dot (the white 2000 VW Jetta 2.0 which broke the timing belt) failed, one of the theories for not starting was a crank position sensor. The thinking is that if the ECU doesn't know where in the revolution the crank is, it doesn't know when to fire, so it doesn't try. It is not as clear whether a failing crank sensor would prevent the fuel pump relay from getting a signal from the ECU, however. As much as I have tried to avoid it, it felt like I was sliding into just-swap-parts problem solving. At $35US for the least expensive part-to-swap (crank position sensors start closer to $60US), this can get needlessly expensive very quickly.

Crank Position Sensor (CKP)

A4 Crank Position Sensor

I have mentioned before my belief that the Audi engineers are sadists. Only someone who takes pleasure in other's pain could arrange for replacement items to be so hard to get to. Case-in-point: the crank position sensor. The crank runs the length of the block (obviously), so given a blank canvas, an engineer could potentially place a sensor anywhere along that axis. Chosen location? Directly under/behind the oil filter so you either have to remove the oil filter (forcing an oil change, which arguably is due) OR you need to perform contortions to get an Allen-head wrench in there. If you go this route, consider that the further the bolt comes out, the closer you get to the oil filter. At least there is only one fastener. These sensors have a long lead on them that plugs into the engine harness... behind the coolant bottle. In Nemo's case, this plug was fairly easy to get to. There are methods for testing the sensor, of course.

The Audi/VW sensor has 3 wires, from pin 1-3: power | signal | ground where the power and signal connect to the ECU and the ground finds its way to the chassis. To test, 12V and ground need to be supplied to the sensor plug (once disconnected from the harness) and a multimeter checking the signal wire for an AC wave signal while the engine is turning. No signal = bad sensor. Since no local shops had a CKP, I returned to sanding Bondo in Zed while I waited for the part to arrive.

Once I had the part in hand, I checked the resistance between the pins. I got 500ohms +/- between the middle pin and one of the outer pins. Using that as a baseline, I swapped out the CKP and then tested the one I had just removed. Same resistance. So, I concluded there was nothing wrong with the old one and put it in the stash of A4 spare parts (with the fuel pump relay).

ECU Swap

At this point, I had run completely out of ideas fo4r why the ECU was not sending a "go" signal to the fuel pump relay. I hit the local junkyard looking for a just-dropped-off A4 to scavenge the ECU. None of the A4's there had the right ECU, but I did get an ECU box cover: Nemo's had a good-sized hole in it where I thought water might have entered. Without another option, I hit eBarf and found an ECU with the same part number as the one as was currently in Nemo at a salvage yard on the East Coast (with a 30 day return policy!). Hopeful, I swapped out the ECU's which consisted of pulling out the big plugs in the back of the old and plugging them into the new one, since the box was still lid-less. I had some concern that energizing the ECU could fry it if the underlying condition still existed.

Still, I turned the key to "RUN" anyway... and heard the radiator fans and fuel pump cycle for a second before shutting off. This was how things used to work. So, I turned to start and he fired right up. I have concluded that my first guess was the correct one: I had left the hood open a little bit to make room for the alligator clips on the trickle charger, and with the hole in the ECU box lid, water got into the ECU and partly fried it. If I had not had the experience with the chipped ECU for Hapy when the computer semi-worked, I would not have been so quick to accept this. The Check Engine Light lit, so the A4 chat-boards all assume that means the ECU is fine. NOT TRUE. It could be partly damaged, like Nemo's.

The climate control is still in pieces, the lower dash panel is off, and the radio wiring, well, it's the same as it was: a mess. While I can move Nemo out of the way so Oliver can go for a spin, Nemo is not ready for driving around just yet. The re-assembly will wait, and I'll probably post on at least the re-wiring of the stereo plugs that the idiots at CarToys cut apart. I did, however, install the ECU box lid, complete with threading in the screws to hold it tightly shut. No more water getting in there.

Thanks, as always, for following along-