Because I can't wade through the verbiage here, I'll put in perhaps some
redundant info. Tess, your engine runs for a few seconds? You're
almost home.
Our '86 LJet Spider fuel pump runs only a split second after the key is
turned on, then stops until something makes the engine turn over. I
think the ECU uses the crank sensor to determine whether the engine is
turning, and therefore eligible for fuel. We had a chronic lean problem
because of an AFM problem. You could have dirty contacts on the wiper
inside, for instance. We had a P.O. with "muss with stuff" syndrome,
and it took us 2-3 months post purchase to discover and correct the lean
issues (thanks to the helpful writeup by Greg Gordon, et al.) a few
years ago.
We started our project by co-opting the cold start injector fuel line to
attach a mechanical oil pressure sensor. This gave an in-cockpit fuel
pressure monitor while we used it. Once you get the indication of
whether the fuel pressure dies before or after the car stalls, you can
re-attach it to the CSI. We mimicked the cold start feature with
starter fluid to get the cold engine to run.
If you disconnect the tube connecting the fuel pressure regulator to the
intake plenum, you goose up the fuel pressure by several psi and
increase the fuel flow a bit more than the ECU thinks it's commanding.
You need to plug the leak into the plenum, but that is easy. This is
useful for diagnosing lean conditions. Also, use the tip in Eric
Russell's writeup on Greg Gordon's website to tap into the O2 sensor
sense line with a voltmeter and watch it for rich/lean conditions. You
should see about 1/2 volt (0.5 V). We were getting not many millivolts
until we sprayed burnables into the intake. This is A Really Clean
Indication, a not-to-be-missed tip. Then the engine leaned out and the
O2 sensor voltage rose to readability. These were our conclusive
indications of chronic lean mixture.
We learned that with over-lean conditions, if you punch the throttle and
immediately let up, doing this roughly once every second or two, then
you can increase the average fuel flow the engine gets and ours actually
would run this way. Once it warmed up, it would idle on its own, but it
wouldn't get there without being punched. This -might- be due to the
fuel pressure regulator getting a higher reference pressure (like
pulling its reference lead from the plenum and leaving it open to air).
Maybe it's the transient higher AFM signal that the ECU gets, and it
doesn't shut down as quickly as the AFM signal does.
If you verify whether the fuel pump is shutting your engine down,
whether it is getting overly lean fuel/air mix, and that the fuel
pressure is OK, then you're about as far along as I can help with.
These were our problems. You may have them and/or others.
Michael Tiefenback
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