MGB - fuel tank R, R & R

Today's post covers the Removal, Refresh and Re-install of the fuel tank. The tank was removed for safety concerns while welding in new floor pans. I discovered, though, that there was a tiny leak at the rear and I had concerns about the viability of the fuel level float/sensor.

Standard Safety Precautions
Like any job, block your wheels, put it up on jack stands if you can't work on it while it's on it's wheels. Since you're working with fuel, at the very least make sure your garage doors are open with a fan blowing on your work area or better yet do this job outside. Obviously, don't smoke or have your friends/kids/wife playing with a welder or blow torch while you're doing this. I'm not your mom, so if you choose to slide under your car without eye or face protection, that's entirely up to you. Personally, I like being able to see things like sunsets and my wife's face, so I wear at least safety glasses, if not a full face shield anytime I'm working on a car. Honestly, the number of times I brain myself on my car has me thinking about wearing a hardhat too.

Free Your Lines
Fuel tanks are all very similar: there's a big hose to get fuel in from the pump, a small hose to supply the engine with fuel and there are vents (at least one) on the top that have lines that lead up to the engine (after routing through charcoal or something) for inclusion into the air that the engine uses at combustion time. On fuel-injected vehicles, there is an additional line for a return from the engine. When the engine doesn't require all of the fuel that the system has pressurized, like when you're decelerating, the excess flows down that fuel line back into the tank. So, once you know what you're looking for, you need to remove them from your tank before you remove the tank itself. First, remove the vent lines. these may not be the easiest to get to, but they will definitely NOT have fuel in them, so you shouldn't need a pan. Make note of where the rubber hose came from when you set it aside. You'll want to cut a replacement that's the right diameter and length at install-time.

before

Now, grab a pan. This is gonna get messy. Hopefully, you knew this day was coming and you already ran the tank to as close to empty as you could before you got to this point. If you have a full tank, this will take a while. Lying under your fuel tank, consider the rubber hose leading out of it. The VW bus was "gravity fed", meaning that the outlet is at the lowest point of the tank. Gravity sent the fuel to the outlet. This is one of the biggest fire hazards in the bus. If the fuel line ruptures, the tank will empty through that outlet right on top of the passenger-side heater box and axle. In the MG, like most cars, the fuel is not gravity fed, rather the fuel is pulled from the tank by a pump. This means that in order to drain the tank you'll need to create suction. I guess you could wire the pump to run the fuel into a pan... Regardless, there is fuel in that supply line, so slide the pan under the connection where the rubber meets the metal line that runs to the front of the car. Remove the rubber line at that connection and allow the fuel to drain out of both the metal line and the rubber line into your pan. There shouldn't be much fuel in either.

trunk underside - before

Now the fun part. We are going to siphon out the fuel with a MityVac. Set your MityVac up so that there is the liquid catch-bottle between the hand-pump (vacuum creator) and the rubber line. Create vacuum until fuel is dripping into the catch bottle and then pinch the rubber line with a pair of pliers. Remove the rubber line from the MityVac catch-bottle, and point it at your catch pan. Hold the end of the rubber line below the lowest point of the tank (and into the pan) and remove the pliers. Fuel should pour from the line into your pan until either your pan overflows or the fuel level in your tank meets the top edge of the outlet inside the tank. Wrap the end of the hose with plastic wrap so it doesn't drip all over you during the drop step. If you have a drain for your tank, slide your pan under the drain and remove the drain plug. These tend to send fuel all over the place when the tank has a lot of fuel in it, so it's best to siphon as much as you can before you open the drain. Ask me how I know :)

Last, remove the filler hose. In the MGB, this was the easiest part. The filler hose runs from the rear next to the passenger tail light through the trunk and into the top of the fuel tank. It is secured with a simple, albeit big, hose clamp.

Unwired
Before you can drop the tank, disconnect the wires from the fuel level sender. Depending on the car, the fuel level could have both a signal wire and a ground -OR- it may only have a signal wire. This means that the sender gets it's voltage difference basis from a ground through the tank itself. If this is you, consider a means of improving that ground, especially if your fuel level gauge is a little flighty, like mine.

Tank Out
This is the fun, satisfying part. I put my ATV jack under my tank to support it while I removed the nuts and bolts. Since there will inevitably be some fuel left in the tank after siphoning, you don't want that weight bearing on the fasteners, and then have the tank suddenly drop when the last one comes free. Some tanks are held on with a pair of straps. My old Camaro was like that, and many older American cars are too. These come off with a couple of bolts. The MGB tank is held on with nuts/bolts around the outside lip where the top and bottom sections of the tank come together. In total, there were 9 fasteners: four along the one side, 3 along the other, 2 across the rear. I guess the engineers couldn't make up their minds and be consistent. The ones in the rear can be a little tricky to get to. Once out, the rear edge of the tank can get hung up above the bumper so tilt the front down first and slide forward.

Drain, Clean and Dry
Once on the ground, remove the fuel level sensor. On the MG, it is held on with a spin-on ring that lets go after a couple of taps with a hammer. Set the sensor aside for testing, and then drain the remainder of the fuel through either the fill hole or the fuel level sensor hole. Depending on how old the gas was, you may need to recycle what is now in your catch-pan. Mine was relatively fresh so I used it in my lawnmower.

At this point, I refer to my friends at Mac's Radiator. They cleaned, lined and painted the tank for the bus a few years ago, and I want the same treatment for the MGB. For about $300, your original tank is better than new, you don't have to pay oversized shipping, you know it will fit and best of all... its a genuine shipped-with-the-car original part. In the MGB case, you can no longer buy a true original. The aftermarket tanks generally don't have splash baffles (prevents the fuel from sloshing around when you corner), and some don't have vents. They aren't lined (so they may start rusting from the inside) and they are of inferior, thinner steel. Still, I did find one for $170 plus shipping that "are made with corrosion resistant Ni Terne steel to fight of rust and ethanol fuel". This is from a less-than-best distributor here in Oregon (poor return policy), British Parts Northwest, and again, it isn't lined. Part link here. Of course, good work isn't fast, so it will be a couple of weeks of waiting before I have it back, ready to install.

While your tank is at the radiator shop, test the fuel level sender. Rather than re-hash, here is a fantastic article for testing and calibrating the fuel sender and gauge. My float would not give a consistent reading below about 100ohm (or from a half tank to full tank), so it will be replaced.

Parts
The parts list is actually longer than I had anticipated. Looking at the picture above, the newer shaped tank is on the right. It bolts up directly under the trunk, so rather than having steel on steel, there are foam "straps" that fit between. There should also be a seal around the edge of the filler neck. Add the fuel-level sender. I also added in a new sender seal and locking ring. Of course, I'll be using all new 5/16" fasteners and rubber lines from the tank to vent and engine fuel-supply. Once assembled, everything related to the fuel tank and supply to the engine will be refreshed.

Placement Prep

trunk underside - after

So, the tank is out and off to the radiator shop. We're waiting for parts. Ugh. I hate the waiting part. To make the most of the delay, I grabbed my face shield, my angle grinder and a wire-wheel attachment and set to clean up the underside of the trunk. Before I got down to it, I shot the surface with Simple Green and a scrub brush. That's all it took. I hosed it off, and it didn't need any additional prep. I could have ground off the undercoating, but there was no need. So, I just shot it with some paint to help it last longer. Even though no one will ever see it, it sure looked pretty when it was done. I did a bunch of clean-up on the trunk floor and the rear bulkhead at this point as well. I'll post on that later, if I remember to.

Tank Prep
When the tank is returned from the radiator shop, it should have a protective coat of paint, but if your shop is anything like Mac's, they highly recommend a thicker, more protective coating. So, sand an edge into their paint, then prime, sand, wipe and paint with a suitable topcoat. Since this is not going to be seen, this doesn't need to be the expensive body paint, but something chip-resistant makes sense, since it will be exposed to the road. Once cured, install the level sender with the new seal, making sure the fuel pick-up tube is pointing toward to bottom of the tank.

after

If you got the new fastener pack, it includes little clip-on bits that act as an a-fixed nut on the tank for the loose bolts that are placed from the trunk. Be mindful to put the new ones where the old ones were removed. Not all of the mounting holes should have these clips. Some of the connections are with welded-in studs hanging down from the underside of the trunk so if you don't get the clips in the right holes, you won't be able to install. This is one of those "a picture is worth a thousand words" moments. See the blue tape in the picture for reference.

Since the steel tank sits up against a steel trunk floor, the MGB was originally outfitted with foam strips to set between. As you can see by the parts picture above, these foam strips run front to back. They are purchased as a roll and need to be cut-to-fit., It is very possible that you could save a few bucks and get basic home insulation strips at a big box store. The parts vendors assure me that the real deal are gasoline resistant, so the extra few dollars are worth it. Your choice. I bought the real parts since I was getting a bunch of other stuff anyway.

Last, set the foam collar around the fuel filler inlet. This needs to be in-place before the tank is installed.

Tank In

With new fasteners in hand, set the tank back on the ATV jack, roll it under the trunk and raise it close to where it will reside. Remember that the rear-end of the tank tends to hang-up, so tilt the tank so the rear end installs first. There are two studs on either side that are permanently attached to the trunk floor. Use these to center your tank, and lightly finger the nuts on (after the washers, of course). Now, you can drop the 5 loose bolts through the other holes in the trunk, making sure to include the large washers (first one nylon then one steel) between the bolt-head and the trunk floor. These will line-up with the clip-on bit/nut things. In my case, the clip-on nuts on the rear of the tank slipped on install so I had to poke at them with a long screwdriver to get them to line up with the holes. Take care as you tighten things back down, making sure that the foam strips do prevent steel-to-steel contact.

Re-Connections

the contrast between new and old

Using new rubber hose, re-connect the tank outlet with the steel fuel-feed line. Then re-connect the return line (if you have one), the vent lines and the big fuel hose. Last, reconnect the fuel level sender wire(s). Make sure you didn't leave anything disconnected, like the drain or one of the fuel-carrying lines. If you haven't looked at the hoses under the hood, now is the perfect time to do it. I found that the hoses near the tank were relatively new (PO replaced the fuel pump), but the lines under the hood were stiff and ready for replacement. After a final once over, put in some fuel, test fire the fuel pump a few times to prime the fuel line and you should be good to go.

That's it for today. I only got after the fuel system because I had to do some welding, but I'm glad I did. Rust hides. If you don't get into the little crevices, you won't see what's growing until it's too late. The top of the tank looked horrible, but once the rust was arrested, the remaining steel was thick enough to last another 40 years. As always, thanks for following along-