Oliver Fuel Fun

Boo had to work on Easter, so I had a Sunday to work with. Knowing others around the neighborhood were celebrating Easter with their families, I wanted to keep my noise and smoke to a minimum. So, I started slow, throwing Oliver onto a charger and then doing inside stuff. By 11, I was mowing the front lawn with the electric mower. With hand tools, I fixed the gates to the fence by lowering the little swivel wheels and re-setting the patio block they set on. Now, the gates sit mostly level and mostly vertical. By 2PM, most of the family gatherings were breaking up, so I felt I could make engine noises and such. So, I headed out to the shop. Engine noises. Ha. Such optimism.

 

No Start

fuel works

I am sure this comes as no surprise, but my first attempt to start Oliver was not successful. I really didn't expect it to, tho. I had a little over a gallon of gas in a jug that I poured into the tank, but I noticed that the fuel pump noise never lessened. So, as I walked to the rear of the car, I expected there would be no fuel in the filter. And there wasn't. The series of things the fuel needs to pass through before arriving at the pump is: fuel level sender / pick up tube -> flexible fuel line -> clear plastic fuel filter -> flexible fuel line -> fuel pump. From there, it travels, at pressure, thru another flexible line, through a short section of 90* hard line, more flexible line and then to the hard line that runs along the frame to the engine compartment. That's a lot of junctions. I started at the pump, testing with a MityVac vacuum pump, working my way back towards the tank. In retrospect, it would have been smarter to work my way forward from the tank all the way to the carb. Lesson learned.

 

Fuel Shower

upper one is bad

One of the short hoses was bad, but there was nothing visibly wrong with it. The picture on the right here is of those 2 lines. The top one cannot hold vacuum; the lower one can. This serves as a great reminder for those driving gravity-fed fuel system'd vehicles like the old VW bus. Fuel lines fail, sometimes not that long after you've installed it and sometimes you can't tell from looking at them. For a gravity feed system, you discover the leak after you've filled your tank, and it gushes onto the ground it you're lucky. Onto your hot exhaust if you're not.

 

While looking for the cause, I cracked the fuel level sender on the tank to confirm that I had enough fuel. I did. Once the one short line was replaced, I went up front, turned the key and started looking for another leak. I did not have to look very far. Immediately forward of the fuel pump, I had fuel going everywhere, running down the rear differential.

 

I concluded that it was another short hose, but noticed that the combination of short hose, weird 90* hard line, longer hose made little sense. I think I did that when I installed the fuel pump because the outlet of the new fuel pump was not clocked the same as the original and I didn't want a kink in the hose. If I remember correctly, I had already cut that longer hose, and solved the wrong problem. Or solved the right problem the wrong way. I think, that 90* bend was from the original system to go from the sender to the pump, and in this installation, I have a clear plastic fuel filter serving that function. Regardless, I corrected this time with a longer hose that runs from the pump to the long hard line. The longer hose was long enough to have a gentle arc, preventing a pinch in the line I was probably trying to avoid with the weird combo of parts. In the bottom picture, you can see that I have a small fuse for the fuel pump. This was not there stock, but I felt that with so many things living on the switched circuit, having a fuse around the fuel pump was probably a good idea.

 

Still No Start 

fuel pump

With the rear end lines set, I turned the key again, and the fuel pump quieted down after a few seconds. I looked under the car and no puddle was forming. There was not a drip at all. I went to the engine compartment, and there were no leaks there either. So, I tried to start it. No love. By now, it was approaching 5PM, and I had to get dinner started. But first, I wanted to know if the hard line was blocked or if there was fuel at the inlet on the carb. I removed the fuel line and gasoline dribbled out. Win. We have fuel at the carb. I put everything back together. Before heading inside, I checked the lights and hazards to give myself a little "well that works" energy before calling it a day.

 

Wrap Up

That's as far as I got on Sunday. After the random home-repairs, I had left myself more than enough time, had Oliver actually started, to give him a deep cleaning. That still needs doing, but first I need for him to run. I rebuilt the carb a couple of years ago, and the engine ran with it on there, so I don't think the issue is fueling, but it still could be. I will start with the spark plugs next time, and confirm I have spark. It is absolutely possible that something worked free during the move into the shop. If that does not bring me the start I am seeking then I will re-examine the carb. Maybe some gas residue became a thin varnish holding the bowl float, or is clogging a jet or something. 

 

That's all for now. Thanks, as always, for following along- 

MGB - Side Draft Carb fun

Today, I return to the little British car: our 1978 MGB, Oliver. Oliver has sat unused for too long. I had been having considerable and increasing trouble just getting him to start and run. So, earlier this year, I removed his carburetor for dis-assembly, cleaning and re-assembly. I did the removal and tear down what feels like months ago, and just completed the re-assembly. So, while this post may feel like a couple of consecutive weeks of fun, it's really a little from March, a little from June and a little from last weekend.

Removal and Tear Down

re-assembled

As is the case with most things on a small car, removing parts requires some flexibility not needed for larger cars of this vintage. Still, removing a carb is not complicated, but I encourage you to take pictures. If your life is anything like mine, you may intend to be back to this in a few days, but days can become months really fast. Anyway, remove the air cleaner. Remove the fuel line (pinch it off first and then plug it). Disconnect the throttle and choke cables. Then remove the carb from the intake. With the side-draft weber (DCOE) and this SK Racing/OER carb, it is held to the intake with 4 nuts threaded onto studs emerging from the intake. The DCOE and SKRacing carbs use the same intake, by the way. Once removed, I stuffed rags into the intake to prevent critters from climbing into my engine, closed the hood and re-covered him. I took the carb over to a bench in the back of the little garage attached to the farmhouse.

At the work table, I started with the most obvious things and worked my way inward. First, the inspection cover and top half of the carb was separated from the main body. I removed every slotted bolt and whatever lay beneath, taking pictures as I went. Last from the top were the air correction jets and then I removed the set screws that held the venturi to the main body. The main body was effectively disassembled, so I shifted to the top half, removing the float, the fuel inlet bits and the choke bits. Last, I pulled the little cover or plate that faces the intake when installed. I am sure someone who does this often would have done it faster, but I needed to chronicle it so I could re-assemble later.

Carb Cleaning

remove from car day

I started like most folks probably do: shooting the carb with rattle can carb cleaner and gently scrubbing it with a toothbrush. I focused mostly on the exterior with the brush and let the carb cleaner do it's magic on the little holes without brushing. Satisfied that I got the worst of it, I pulled out a razor blade and removed all of the gasket bits and rubber seals. Then, put together a ultrasonic cleaner soaking tank with solution designed for carbs. I had read online that some folks will use Simple Green or other things, but I figured the correct solution was far less expensive than a replacement carb in the event those advisers were wrong.

The cleaners, well, the one that I got, but from what I read, many of them have a setting to warm up the solution while doing the ultrasonic. From what I read, there was some level of concern about how well they actually maintain temperature and that sometimes they can run the solution too hot. Since the solution is concentrated (read: need to add water), I decided to use boiling water and when poured into a room temperature solution, the overall temperature would be sufficient. I ran the carb body and all of it's pieces in the ultrasonic cleaner for multiple 20 minute cycles. Once I was satisfied that the carb was as clean as it was going to be, I moved it and the parts into a bucket and rinsed them with water. I then set everything out in the sun to dry.

Rebuild Kit

great kit

Unlike a Weber DCOE, the SK Racing/OER carb is not exactly common in the US. It is not generally sold here; it is much more popular in Japan. So, finding a rebuild kit for an obscure, foreign and old (time is relative) car part was time consuming on it's own. I was able to find a single supplier of a kit, a person in Japan with a storefront on eBay (Bprojects Japan). While I have a healthy skepticism of eBay sellers, deals and parts, I really had no other choice. The kit I received was incredibly well set. It included the major gaskets, replacement air correction jets and springs, new crush seals for the pump jets, a pair of ball bearings for the "pump non-return", a pair of copper crush seals for the fuel inlet and a big collection of rubber o-rings. It really had everything except a manifest indicating what part number each bit was for and the gasket for the jet inspection cover was missing. At this point I realized that I took pictures of the disassembly, but failed to take pictures of the rubber seals as I cut them off.

Re-Assembly

view from firewall

With my laptop open to the SK Racing carb manual, and my phone open to both the pictures I took and a blurry exploded view drawing of the carb, I started putting it back together. I started with the last picture I took and worked by way backwards through them. The only step I took that I had to undo and do again was the placement of the gasket between the top half and the main body. I had assembled the float, but the gasket needs to set above the float, which had I thought about that for a second, it would have been obvious. The float did not fit in the opening in the gasket, nor does it ever need to along its travel path. Also confusing was where the pair of ball bearings and small rectangular rods went. Process of elimination worked well here, choosing to do other things until it was apparent what hole those dropped into.

I used liquid gasket-maker for the jet inspection cover. That stuff makes a dark sticky mess. The instructions on the bottle say to let it dry "for a few minutes" before putting the 2 pieces together which need a gasket in between. I let that sit for well past the recommended few minutes and it was still very wet.. and even after letting it sit in the sun the stuff didn't dry very much. So, I did everything else install-wise and add the inspection cover dead last.

While I had the carb in hand, I decided to add a heat shield to the underside. The header that I installed has a thermo-barrier powder coating on it, but I know from having the hood open after driving it that a ton of heat is still getting into the engine bay. I suspect the source is the header (or the radiator), and the best thing I could do for the carb is to help prevent heat from getting to it. So, I got a DCOE carb heat shield from Pierce Manifolds. The mounting bolt pattern is designed for a Weber DCOE, but the SK Racing/OER is exactly the same in this area. The venturi maintenance holes line up, the cut-outs for the intakes, etc. it all just lines up. The heat shield is heavier and thicker than I expected, but I expect it will do exactly what it is intended to do: block and route-away heat rising from the exhaust.

Install

re-install day

As easy as the carb was to remove, installs always take longer. This bugger was no different. First, the carb mates to the intake with these thin (maybe 6mm thick?) plastic isolator bits between the carb and intake. On each side of the isolator resides a rubber O-ring that is set inside a groove. So, you are managing a carb, 2 isolators and 4 O-rings at one time. That required some dexterity.

I discovered that the heat shield has a small tab on the intake side that would hit the center header pipe. Recall, the MGB has a Siamese head, so the middle 2 cylinders share an exhaust. The PO had a home made exhaust manifold with a center pipe effectively pointed straight down. The header has a more typical curve. So, the heat shield came off and I adjusted that tab to point angled upwards so it did not hit the header pipe, but actually will shield the top-most end of it. Then, I realized that I could not address the lower mounting studs with heat shield installed so I removed it again, re-installing after the carb was nutted down into the intake.

From there, the install was about what you would expect, complete with a dropped bolt under the car. I had to reverse the spring-return arm on the carb as well as flip the fuel inlet. Still, it was relatively smooth, hooking up the fuel line, control cables and air filter.

No Test Fire

By this time, I had sweated my way through most of a summer afternoon and cleaned liquid gasket maker off my hands more times than I'd like to count. As much as I wanted to enjoy the sound of the engine running, I chose instead to take the limited win: Oliver was in one piece. Boo and I went to the county fair instead of test-firing Oliver's engine. Now, Oliver is covered back up, again waiting for me to have a few hours to test fire his engine and fiddle with settings. I sincerely hope the tear down / deep cleaning was what he needed. I'll post an update when I have one.

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That's it for today. 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-

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-

MGB - Fuel Pump 2 Step

Picking up where we left off with Oliver, the 1978 MGB, we had completed the ignition swap out and we were ready to start the engine and set the timing. Until the battery went flat.

To Start Or Not To Start

AutoZone product picture

At this point, I was ready to test-start it. Or, so I thought. Last Fall, I thought Oliver's battery was going bad. It later turned out to be the clock sucking all the juice while left sitting for weeks (see MGB Battery Monitoring). Before I learned that, however, I swapped the battery out for the battery from the donorZed. At this point in my electronic ignition install, I discovered that the donorZed battery actually was bad. I mean bad. Like, I would put it on the charger overnight and then I could put a voltmeter on it and watch it discharge down to 0. Fortunately, I had left Oliver's prior battery on the trickle-charger, because I guess I was not 100% convinced it was bad. So, I swapped his old battery back in. I turned the key, heard the fuel pump click once, and then heard nothing. In the past, I have had this happen when the fuel pressure had not let off since it was last running. Since the engine had not run since October, that was unlikely. Perhaps the inertia switch got nervous and is preventing the fuel pump? Well, then I would not have heard the one click. Still, I pushed the reset button. No change. Then, I jumpered around the inertia switch, running the wire disconnects through a 3A bladed fuse instead of the inertia switch. Same single click.

Fuel Not Pumping

what arrived

I concluded that the fuel pump, which had not been behaving consistently (sometimes just not working at start up), needed replacing. I slid under Oliver's backend and recalled that the original fuel pump had been replaced by the prior owner for what looks like a universal pump. I can't judge. Quite the contrary, I was not going to invest in a $200US+ original MG fuel pump on the assumption that the fuel pump is the problem either. So, I ordered a Spectra fuel pump from AutoZone for $48US delivered next-day-ish. This pump meets or exceeds the requirements for pressure (3.8psi) and delivery volume (18gph) for an otherwise stock MG engine. I sourced the requirements from this page on the MG Experience. The Spectra offers 2.5 to 5 pounds of pressure and 21gph, has reviews on Azn from MG owners saying they work great and even AutoZone shows these are a direct replacement for the Midget.

It is possible to over-power your carb with too much pressure, so that's one for the back of the mind while trying to diagnose what's going on with the fuel flow through combustion. I may introduce a pressure regulator, but one could argue that adding a cheap pressure regulator on top of a cheap fuel pump starts approaching the cost of a good stock-style replacement pump. While that's very true, I am not running a stock carb either. The prior owner installed a SK Racing (now known as OER) side-draft carb, which seems like a combination of the Mikuni PHH and the Weber DCOE, but this blog post has some great information about them. My knowledge of carbs is extremely limited, so I am accepting this as a learning opportunity.

Fuel Pump 2-Step

Holley Mity Mite

The pump that arrived was not as pictured. Lovely. This one was equipped with a 3/8" barb on one end and a 3/8" NPT female on the other. Into the 3/8" NPT, the consumer was expected to thread in the included mini-filter that has a 3/8" barb on the end. While I am sure a filter is needed, that one they included is tiny and virtually irreplaceable. Perhaps these pumps don't last past a fuel filter change. Since the pictures and the spec's I could see did not match, I was not going to go forward with it; I already have more than enough mysteries with the fuel system. I returned it unopened and got a Holley 12-434 Mighty Mite Electric Fuel Pump. These top-out at 4psi, push 28gph and actually ship with 5/16" hose barbs. Between the delays from CoViD and possible delays from that cargo ship that was blocking the Suez Canal for a week, the arrival of the fuel pump was not exactly immediate. Still, through the power of split-posts, it arrived in time to keep this blog active.

 

Fuel Pump Swap

The pump arrived mid-week, so I started my Saturday planning for the fuel pump swap. Over breakfast, I prepped the wires and assembled the pump and pre-filter. While the Spectra above also delivered with a filter like this, I know that Holley supports replacement pre-filters (I verified on their website). Either way, I figure I have one of those in-line clear filters just upstream of the pump, so I don't expect it to require service too terribly often. For the wire prep, I attached a male wire disconnect to the ground (black) wire and a male disconnect to the positive (red) wire.

ready for install

So, with the pump in one piece, and wire disconnects attached to the wires, I slid under the rear end of Oliver, bringing a collection of tools, a drain pan and a flashlight with me. I closed off the fuel supply from the tank with a small pair of vice-grips. I then moved from that hose forward through the fuel pump, disconnecting hoses and draining the contents into the pan. I only got as far as the pump before I didn't need to drain anymore. Clearly that old pump was not working anymore.

The MityMite is actually larger and heavier than the universal pump I had removed. So, I needed to adjust some fuel line lengths, but otherwise things just fit together. I reused the bolt hole which was holding the old pump to the front edge of the trunk, for example.Once all together, I wired the black wire to the grounding wire that was previously attached to the ground tab on the universal pump. Into the female disconnect coming from the pump, I put one blade from a 3Amp fuse. I put the other blade into the female disconnect which is ultimately wired to the inertia switch. I worked the disconnects with a pair of pliers to get the fuse to stay firmly in place. I wrapped the disconnects and the fuse with electrical tape. Last, I spooled up the extra wire and zip-tied it to the pump pre-filter so the connections would not shake loose.

Pump Test Fire

With everything as I thought it should be, I removed the vice grips and my tools from underneath. I turned the key to "RUN" and the pump fired right up. I left the key in "RUN" and checked the fuel lines for leaks. None appeared, so I concluded the pump was fine. Hoping for the best, I returned to the driver seat and tried to start the engine. Oliver would not start, but the engine would turn. That's a start. I removed a spark plug and I could smell gas on the tip, so We now have fuel and electricity. Next, we need to get electricity to the plug... at the right time.

Recall from my last post that my initial effort to find TDC were wrong, and that I needed to pull the valve cover to figure out true TDC? Well, I did that here. Still, even with true TDC found, Oliver would not start. I did figure it out, but that's my next post.

Thanks, as always, for following along--