87 930 - Fuel System Help

[dakotaspeed]

While Driving my 87 930 a few days ago, it started to stumble like it was running out of gas.. then it quit. After a few minutes I tried to start it and it caught and quickly died.. Now I faintly remember that there is a Fuel injection problem that used to require carrying and extra relay or something. Can't quite dig it out of a foggy brain.. Could that be the problem? or something else?? This is a recent professional rebuild motor. Where to Start?

[javadog]

You're probably thinking of the DME relay that is used on the Motronic Carreras, not on a 930. Check your fuel pump fuse, your fuel pump relays and your fuel pumps. Then, check your CDI box.

JR

[heliolps2]

you should go on the 930 theard, You will get alot of help their

[Shadetree930]

As stated above:

Check your fuel pump fuse (#6)

Check/jump your fuel pump relays (2 round red relays in trunk)

Check/jump your yellow overboost relay (in engine compartment)

Check the ground on the boost pressure switch (white/ivory pressure switch)

I would start by jumping the yellow relay. That will tell you if fuel pump fuse and fuel pump relays are alive while taking the Yellow Relay out of the equation all in one fell swoop.

Jump the yellow relay, turn the ignition to the on position and listen for BOTH (front & rear) pumps. If both pumps run, points 1 & 2 can be scratched off the list.

This thread has the instructions for jumping/checking each of the above:

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/547032-sticky-common-answers-why-my-car-doesnt-start.html

Instructions at the end of the thread.

[spuggy]

Originally Posted by Shadetree930

Jump the yellow relay, turn the ignition to the on position and listen for BOTH (front & rear) pumps. If both pumps run, points 1 & 2 can be scratched off the list. Don't let them run for very long without the engine running ... you will hydro lock your cylinders.

Pumps shouldn't run without the motor cranking/running on any CIS car after 1974-5 or so. I know that they aren't supposed to on my car (and yet it's been like that for the last 30,000 miles....). If access wasn't so awful, I might get around to looking at that...

CIS injectors don't reach crack pressure and squirt fuel just because the pumps are running. If you do an injector flow test, you jumper the relay (or unplug the air flow sensor plate micro-switch) to run the pumps, and then you depress the flow plate to get them to squirt into the little jars or whatever.

This isn't to get the pumps running, this is to get the piston moving up the bore in the fuel distributor (in response to supposed throttle action/air flow) and open the slits to the delivery side of the circuit. That's what opens the injectors and squirts fuel into the manifold.

Just because the pumps are running doesn't mean that they're delivering fuel. If they both run, you should probably do a flow and pressure test. Minimum flow spec is 1500cc/30 sec, both pumps. System pressure should be 6.0-6.7 bar for a '78. That's probably close enough for government work on an '87...

If that works, I'd probably be inclined to check fuel is actually reaching the manifold (e.g. injector flow test) before diving into looking for more esoteric problems...

Oh, and the car had plenty of good, fresh gas, right? It wasn't sitting for a couple of years with gas in it waiting for a rebuild? CIS doesn't like sitting, and the gum/varnish can really do a number on fuel distributor internals (especially the piston), apart from anything else.

[MJR]

The relay you're thinking of is the ignition delay relay that keeps the ignition on for five seconds after the key is turned off. When this goes up in smoke, the engine won't run. However, there will be no sputtering, it just dies... Sputtering to a stall is a good sign that the pumps are shutting off. The ignition stays on, so when the pumps shut down, the CIS continues delivering fuel to the injectors until pressure bleeds down to the injector opening point, and then it stalls. Like Spuggy said, you can unplug the coupler on the CIS unit and the pumps will run. You'll be able to hear them clearly. I'd start with that.

[dakotaspeed]

Thanks for the help. Loose wire