Hello,
I have been dealing with an apparent vapor lock problem for two years now
and it is getting worse, so I figure it's time to really find a fix.
Here are the symptoms:
On warm weather days (last year it was anything above ~82F), after driving
for 10-15 minutes and stopping the engine, upon re-start of the car the
engine does not appear to be receiving enough fuel, as demonstrated by the
sputtering and loss of power. I can continue driving, but it takes me a lot
longer to get where I'm going (and its embarrassing when in traffic!). The
apparent fuel starvation continues and eventually gets less troublesome
(especially when I get into 4th gear - perhaps a function of the speed I'm
going and the effect of wind cooling the engine??), although it does not go
away until the car has had a chance to sit for at least 45 minutes. This
year the problem occurs in lower temperatures (happened today in 70F), and
it seems to come on more quickly.
Another symptom is that the car has a strong odor of gasoline (stronger to
my wife than to me) after driving - even in cooler temperatures when I don't
experience the vapor lock problems.
Otherwise, the car runs great.
Some observations:
To my untrained eye, the fuel lines look fine. They are not even warm to the
touch from the gas tank all the way to the carbs.
The fuel pump is operating at about 3.25 PSI at about 800RPM. This is below
the pressure specification range of 3.41 to 4.26 PSI at 700RPM, but my
reading could be off due to old testing equipment. Is this a significant
enough difference to be the problem?
Last year I replaced the fuel pump diaphragm due to a tear which caused fuel
to leak out the bottom of the fuel pump. There is no apparent leak anymore,
so I assume that the diaphragm is fine.
The volume of fuel delivered by the fuel pump is sufficient. If anything it
delivers too much fuel. Could too much fuel being pumped cause this type of
problem at higher temperatures?
The carbs do not appear to be running hot (touch test).
The cylinder head is hot to the touch, but the engine does not run too hot
and the car has never even come close to overheating.
Given the strong odor of gasoline, I am starting to suspect the carbs as the
problem.
The car is a 68 2000.
Thanks for your ideas and comments.
Mike
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