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MG TD TF 1500 - Re-formulated gas and leaks

In the last few weeks I have been tormented by a continuous series of small fuel leaks in both SU carbs and fuel pump. Is this a result of using the so called
"summer re-formulated fuels"? Other vintage car owners have been finding the same problems of minor fuel leakage around the area of the gasketing and fuel lines. In some cases the binder in the gasket material
is dissolving into a sticky mess.
The first fuels leaks started at the carb and bowl connection and then around the float chamber cover. Replaced gasket with neoprene O-rings and leaks stopped. Then the fuel pump started to leak out of the small vent hole, this I assumed to be a defective diaphram on the supply side, so I replaced the pump. The new pump however started leaking thru the gasketing within 24 hrs. This weeping leak is small and only emits fuel after pump has been run. (a feed side) I have noticed that if the ignition is turned on, the pump clicks to build up pressure, but every 20 seconds or so it will emit another click which indicates a small leak.

Being in a TF, changing the fuel pump is a PITA.
Anyone have a similar problem or a solution.
colin stafford

Colin, I have seen some new diaphrams that have a plastic of some type covering the rubber to protect it- no clue if new pump has or not. Did you try tightening the pump cover screws? The carb/bowl/float seals are fiber or paper, can't imagine how the fuel would effect them- of course it is possible. I did run across tank sending unit rubber gaskets that turned to jelly in a matter of months a few years ago. I would not worry about an occasional click- the disks in the pump can internally leak, or the float needle valves also. How old were your carb seals? Mine seem to get leaky every few years. Lastly, make sure you don't have a fuel level or needle valve problem. George
George Butz

Collin, definitely not an expert on this. But there was a problem with the winter additives in gasoline.
As I recall it was attacking some of the non metalic parts on some autos but not all. I think the additive is methanol and I believe it is added to help eliminate winter freeze up. If it is indeed methanol it will attack some rubber components.
Dan H.
Dan Hanson

Colin - I suspect that you had old seals that were probably on the verge of leaking and the reformulated gas just speeded things up. The same is probably true of the original fuel pump diaphragm. On the new pump, the leak is probably a case of screws being a bit loose as George suggests. Try tightening them a bit, maybe a quarter turn, but be careful not to damage the screw head so the pump can be returned as defective if tightening the screws does not stop the leak. Your new pump may or may not have the plastic membrane over the diaphragm. Burlen Fuel used this membrane for awhile, but have stopped using it as it caused problems with the travel range of the diaphragm. I always cut the membrane off as I could not get older pumps to run with it in place. The diaphragm material that is used by Burlen Fuel is impervious to all of the newer gas formulations. If you want your old pump restored and converted to solid state, I can do it for you. See my article on SU fuel pumps and write up of my SU fuel pump services at the following web site: http://www.custompistols.com/cars/articles/dd_su_fuel_pumps_101.htm
Good luck - Dave
David DuBois

To all; I believe if you research the problem you will find that fuels with the alcohol added is the problem. Not all fuels have the alcohol but in some states it is permissib;le and I bleieve you will fid this to be the problem
Ellis
Ellis Carlton

Ellis - The alcohol may be a problem in some areas, but the SU fuel pump diaphragms seem to hold up quite well to it as I have not had any complaints about the diaphragms that I have replaced over the years. The Brits seem to have gotten something right in that regard.
Cheers - Dave
David DuBois

Dave the pump that originally leaked, the one with the suspect diaphram, was about 5 yrs old. The replacement was my original pump that was re-built by University Motors about 5 yrs ago. I will pull it out over the weekend and tighten the screws and fittings. I teflon tape the threaded fittings. I also have a set of the red fiber washers type seals which can be changed.
colin stafford

Colin - The teflon tape is probably a better seal on the threaded fittings than the fiber washers (use the washers anyway to take up space). I use Permatex 97B as a thread sealer on the pumps that I restore and then really reef ont he wrench to tighten everything down. I sometimes find that I have to try a couple of times to get all the leaks sealed. The L and HP type pumps are a mass of leaks waiting to happen. Good luck - Dave
David DuBois

David, teflon tape does stop leaks. However, most hyraulic devices carry warning against using it on fittings. Some years ago I had repeated steam trap failures in an autoclave. In frustration, I cut one open and found minute flakes of the teflon tape in the ball seat. Switched to a liquid selant and no more problems.
George Butz

In the TD-TF archives you will find reference to a product called Gasoila. I purchased a tube at a local full line plumbing supply store. As I have serviced banjo fittings, other fuel line or oil line fittings, drain plugs, etc., I have used the thinnest smear of Gasoila on the gasket or threads. I have yet to have one of these fittings leak.

Usual disclaimer....I have no affiliation with the manufacturer.

Larry

From the manufacturer's website:
http://www.federalprocess.com/specchem/index.html

Gasoila Soft-Set Thread Sealant With PTFE

- Soft-setting, non-toxic, PTFE paste.

- Provides a positive seal on pipe threads, joints, fittings, hoses, nozzles, LPG cylinders, pump assemblies, oil burners, hydraulics, bolts, compressors, engines, motors, housings, plugs, fuel lines, couplings, etc.

- For use on brass, copper, stainless steel, aluminum, black pipe, tin, galvanized, ABS, PVC plastics, nylon, polyethylene, polypropylene, polybutylene, etc.

- Excellent resistance to gasoline (up to 20% alcohol and petroleum blends), petroleum solvents, kerosene, diesel oil, propane, butane, LPG, cutting oils, ammonia, aliphatic solvents, acids, steam, water, compressed air and more.
Larry Shoer

Dave, I took the leaking pump apart and found the bottom of the gasket in kind of a mushy condition and it was apparent that some seepage of gasoline had occured. Replaced the seal and diaphram and re assembled pump. Those figure 8 spacers are a pain to get back in correctly. Really cranked down on the fittings and and the screws, added a little teflon dope and no leaks.
colin stafford

Colin - Sounds like you have things well in hand. Keep an eye on the pump for a little while and if no further leaks develop, you should be good for quite a number of years.

George - I am a product of working on nuclear submarines where the mere mention of teflon tape in the reactor compartment will bring things to an instant stand still. It has it's uses, but as you mentioned, one has to be very careful with it. One of the problems is that when it is imersed in a liquid, it becomes almost invisible.
Cheers - Dave
David DuBois

In the forth coming weeks I will be writing an article on older cars and the additives in reformulated gasoline. The MG could be one of the worst scenarios for leaks and fires.
colin stafford

This thread was discussed between 13/10/2003 and 30/10/2003

MG TD TF 1500 index

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