snora

have an '87 951, mildly modified with Vitesse MAF, billet fuel rail/Aeromotive AFPR/Marrin damper/SS braided fuel lines and small alternator/Nissan Quest swap

about month ago car started dying, once a day perhaps; then got worse, finally not starting and/or barely running then dying such that I had to have it towed home

replaced alternator with new one; same problem

replaced filter thinking it was a fuel delivery issue; twice it started, ran fine for a while; thinking the problem solved, turned off motor, took it off stands--then wouldn't start

here is what I know: fuel pressure gauge on AFPR showed pressure to what I had set it (3 bar) when the car was running; jumped the fuel pump--it runs, pressure gauge shows proper pressure

gauge does not show pressure when engine not running--gauge is on the the AFPR--to my knowledge, it never has, but then again I never bothered to check it when things were running fine

pulled fuel pump to see if check valve is functional--seems to be, but not sure how to properly test other than to put in new one

system modifications don't have that many miles on them, 25k perhaps; not sure about fuel pump

does DME relay give intermittant operation sometimes? have not been able to swap in a different DME relay to test it, don't have a spare

injectors were cleaned before installation, but haven't tested them at this point

I have zero additional ideas at this point and would appreciate some input

thanks

donn

mikeyoman

you could jumper DME relay socket pin 30 to 87 & 87b for testing.
This will simulate the DME relay BUT be aware the fuel pump will always be running like this, even with ignition off - but it might prove if the DME is the problem or not.
Fuel pump normally only runs when engine is also running, for safety in a crash situation.

Brantley

When cranking, do you see "slight" tach bounce? Like a 1/16th of an inch? If not then the issue could be your speed / reference sensors.

http://www.clarks-garage.com/shop-manual/ign-02.htm

Have you validated you are getting spark?

Sounds like fuel from your description is okay.

URG8RB8

Sounds like the first thing you should have checked but did not mention, DME relay. I assume you have verified not the DME relay? Does the problem get worse when car is warm? In other starts starts fine in the morning at cold start. Then make a drive somewhere park it for a brief time come back and try to start warm and won't fire? If so, DME relay 95%.

snora

thanks for the replies

in my search of this website for ideas, I did not run across this apparent solution to my issue--not to say it is not there, only that I had not run across it

what had been nagging at me was the behavior of the stock volt gauge--it was going absolutely zero

perhaps should have indicated that in my original post

anyway, decided to try one of my spare ignition relays--number G2

viola--volt gauge comes alive as does the engine

at any rate, here's an additional idea in cases of non-starting vehicle where the volt gauge is gone dead

thanks again

donn