Fuel problems

[jefflee]

Take the reserve unit out complete, fit a piece of rubber hose from pipe down into bottom of tank,
my car then ran perfect for more than a week like this and proved I needed to sort the reserve leak out as luli says.

[chris dancey]

Personally, on prewar cars with this type of double tube system I would seal the shorter main pipe top and bottom and just rely on the reserve draw pipe making sure this is airtight. The early cars had a manual operated reserve that involved cork pistons that invarioubly leak, especially if they get dry and shrink. With the one pipe sealed system this does not happen, the reserve handle is still left in place for show only. I have had no end of problems over the years with leaks and found in the end that this was a secure way of preventing the problem. I keep a dip stick ( a wooden rod ) marked just in case with the fuel levels. Important with modern fuels to keep the tank full ( or empty ) as the fuel is hygroscopic ( absorbs water ).

[TonyG]

I have just had to resolve the problems outlined by Chris on my '37 12 Tourer. The reserve change over mechanism was very worn and the cork seals perished. This meant that there was air getting into the top of the fuel pick up near the union with the main pipe and the whole thing was wet with fuel. I have a SU electric pump and this was working overtime to overcome the air leak and get sufficient fuel to the carbs. To resolve the problem, I removed the reserve change over mechanism and soldiered up the hole where the plunger fitted and the small hole at the other end which, I assume, is there to avoid a vacuum when the plunger is pulled. However, as a departure from the advice below, I blanked off the main pick up pipe and now use the longer reserve pipe as the main feed. This is to ensure that it's possible to get to the fuel at the bottom of the tank, otherwise there would be over a gallon sloshing about after running out! Of course, this is only OK if the tank is in good condition and there isn't a problem with rust and dirt that needs to be avoided.

[chris dancey]

Spot on Tony, Keeping the longer reserve pipe active is what I was trying to say, this is of course the reserve pipe. Like you I now braze up the head and bottom of the main pipe to seal, this prevents the problems of drawing in air.

[wooster]

I removed the valve and the suction pipes from the car and stuck it in bowl of water. I sealed up each pipe it turn (with kids plasticine) and blew down the openings. No air bubbles.

The inline filter (in the engine bay) is transparent and I think I can see air bubbles entering it from the fuel pipe.

Does this mean I have a leak in the pipe somewhere? I don't have fuel dripping onto the floor of the garage.

As always all advise gratefully received.

[luli]

You need to remove the mesh filter from the bottom of the tubes, seal what is normaly the fuel output, imerse the valve unit and the upper part of the tubes in water, seal the bottom side of each of them in turn - and blow air in the other.

[wooster]

That's pretty much want I did. Although there was no mesh filter.

[luli]

Do you have a substitute fuel pump? Which type of pump is it? Have you sealed all unions using Loxeal?

[chris dancey]

I use plumbing PTFE tape to seal joints, works well.

[chris dancey]

I am thinking that the problem may be with your inline filter. Personally I site the filter nearer the pump outlet ( if you have an electric pump fitted..and fitted to the rear of the car ). Might be worth trying to remove the filter and fix a tempory piece of clipped plastic ( or similar ) pipe to see if the problem persists. Worth a go, I have had problems with the glass sided filters on other cars.