>The T.M. shows that the fuel pump should develop between
> 4.5 to 5 psi of pressure. It was suggested that you try a
>gravity fed setup for t-shooting
I will -- should be easy to set up and will put the fuel pump question to
bed.
>Second a coil swap might be in order. Also, dont forget the >condensor, I've
had a few do simular things after they
>warm up.
Hmmm... I tend to forget about that side of the ignition since on modern
vehicles it is so trouble-free, but it could indeed be a problem as you
describe.
>Also, check for any vacuum leaks. Things do move around when
>heated, and with the M38 & M38A1 carbs, the accelerator
>pump is pulled by vacuum and released to "pump" additional
>fuel with the loss of vacuum as if the accelerator was depressed. If you
have a vacuum leak, it can cause weak acceleration and a bad idle.
I looked at the engine vacuum system in detail last time I tried to tackle
this problem. I found that this engine has manifold vacuum going two places:
the wiper motors and the distributor. The vacuum pump is NOT in line with
these as shown in the TM. Could this be a problem? I would expect the
vacuum pump to act as a buffer amplifier (sorry I think in terms of
electronics) stopping nonsense like wiper lines breaking from bothering
engine vacuum.
Vacuum measured at the distributor or wiper line is good, but it could go
down while I'm not looking (driving). Pulling the vacuum line completely
loose does not really duplicate the problem. It does roughen the engine
idle, but it is not the same sound or feel. I guess I could temporarily
plug the vacuum port on the line from the manifold so there is no chance of a
leak on the rest of the lines and see what happens.
I did not know about the vacuum action on the accelerator pump -- could
defintely be a factor.
Thanks for the good suggestions -- I've got some more avenues to explore.
Good thing the kids and wife are out of town this weekend and I am in
bachelor mode!
Steve Johnston
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