John Mitchell wrote:
> Upon checking my oil, It smelled of gasoline, but I have not been
> able to detect and increase in the oil volume on the stick. When I
> had the engine out for bearings over the winter, I replaced the fuel
> pump with an NOS unit because the old pump had leaked into the
> crankcase and had caused the need for bearings. Being NOS would make
> me suspect the diaphragm leaking, but I think it could also be caused
> by a stuck float in a carburetor. Is there someway to sort out where
> the problem is without pulling the pan and looking for the drip? If I
> remove the fuel pump, how can I tell if it's leaking? Thanks for any
> advice. John Mitchell 76 TR6
If I recall correctly there is only the diaphragm between the fuel and
the crankcase. Another source of fuel in the oil ad you correctly note
are leaking fuel bowls that allow gas to leak into the cylinders and
past the rings. The latter is evident with a lot of black sooty smoke
on startup and a lot of carbon deposits inside your tail pipe.
If the fuel pump diaphragm is slightly leaking, you may smell gasoline
in your oil but probably not detect any level change. This is because
it will flash evaporate in your oil, escape through your positive
crankcase ventilation port into the carburetors.
It is difficult to detect a slight leak. The arm of the fuel pump is in
an oil spray area. If you take the pump off and look at the engine
side, and it is washed clean of oil and smells of gas, it is a good size
leak.
Older (New Old Stock for the most part) diaphragms were not compatible
with ethanol, MTBE/TTBE. These additives in gasoline in the USA today
will cause most OE NOS rubber seals and gaskets to swell and deteriorate
rapidly.
The last diaphragm I purchased had a blue layer of some sort of
synthetic on the fuel contact side with the SU logo on both sides of the
diaphragm. This was a genuine SU replacement part.
Chances are if it is an NOS part or pump, or a cheap no-name knockoff,
it will not be compatible with today's gasoline.
Who carries them? Ask around.
--
Glenn A. Merrell
Chairman, Triumph Stag Club USA (2007-2009)
The best trophies are miles on the odometer, stone chips in the paint, dead
bugs on the windshield!
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