Saintrey

-87 S4.
1) Fuse is fine
2) .Relay switch is fine
3) Fuel pump and filter replaced new 2 years ago.
4) There's a 1/4 of fuel in tank

Not sure where it is broken and where to check next. Any ideas?
Would appreciate any help. Thanks.

Mrmerlin

find the fuel pump relay ,
with your finger on the FP relay , turn on the key to run position, does it click? it shouldnt.

Now ,crank the engine , does it click after the engine starts rotating?
It should click after the engine starts cranking.

NOTE please post a picture of your engine bay so the condition of your machine can be ascertained

dzaprev

Go to the back of the car while someone cranks it and see if you hear your pump turn on. If not check for power with a test light while someone cranks it. Now you eliminated the wiring and fuel pump relay if pump does not turn on but has power.

husker boxster

Pull the hose from the fuel filter going to the front of the engine. Put a hose from the fuel filter outlet to a gas can. Try starting engine. If it's dry, your fuel pump isn't running.




Swap your fuel pump relay with the horn relay. Test your horn. If it works, it's not the relay.

Hot wire the fuel pump with a jumper wire where the fuel pump relay goes - terminals 30 & 87. You should have tons of fuel going into your gas can if the fuel pump is good.

If the fuel pump is good, then it's either the CPS or the LH ECU.

Saintrey

At run position, yes it does click and it also clicks when I crank engine. Hmm.
The fuel relay that's on it is from a running engine. I switched it with my other '87 S4 (yes I have 2 '87 S4)
I also switched the LH and EZK relay switches. My other S4 runs and starts after doing this switch using the non-starting-S4 relays so I believe the relays are all good. Yes?

But let me give a bit of background. This not-starting-S4 caught on fire when I replaced the fuel injectors 1 1/2 years ago.
I bought the other S4 so I can put this back together and I did but it would't start but the issue was no 12v going to the fuel injectors. Fuel was ok and going to the rails.
At my wits end, I decided to bring it our local Porsche dealer to diagnose. They did and they found out the injector harness I put in was the wrong year - an 89 vs 87.
I then procured a used one from 928intl.com and installed it earlier this week. And finally I have 12 v to the fuel injectors but now no fuel to the rails.

Hope that all make sense. I appreciate your ideas. Let me now if you have more. Thanks!

FredR

Are you assuming there is no fuel to the rails or do you know that based on..?

Saintrey

Thanks for asking. I base that on after a few cranks and non-start, I unscrew the fuel rail bolt connector from pic and no fuel comes out which normally there would be. I continue to crank starter while it's still unscrewed
and still no fuel comes out.

Is there another way to check?

Randy V

I see your problem.

But check the fuel pump relay and fuse first.

Shark2626

😂 There are many ways to check. But man, for a guy who has already set his car on fire once you certainly picked the right one for you! (Sarcasm)

You should see fuel doing the inspection the way you did, so you are correct the fuel pump is not pushing fuel to the rails for some reason.

Can you check to confirm that your fuel pump is actually pumping fuel?

Saintrey

I have. It's a new 15amp fuse. Even checked it for continuity before plugging it in. The relay is good as it came from a running engine. Thanks.

Saintrey

That's the next thing I'm going to do is check fuel pump but needs some time to do so will get to you and others a bit later. Thanks guys!

j.kenzie@sbcglobal.net

Fuel pump not pumping. You should be able to hear it whizzing away, while the FP relay is jumpered 30 to 87. If not check for power to FP also with relay jumpered. You may be able to aply power directly to FP. I have heard that sometimes you can reverse FP polarity to unstick a stuck FP impeller. May be trending towrd new FP and new fuel filter (not new since fire). You may want to drain tank and be sure no debris present then add some new fuel. Just some ideas. You may want to get a fuel pressure gauge. I would not crank the engine with an open fuel rail, unless you have ignition disable and then only for the briefest time, with somebody watching. Even then, I'd find another way involving at least a hose into a container.
Good luck,
Dave

Saintrey

Thanks for the ideas. Yes I have somebody with me (wifey) while cranking engine. And a rag underneath rail to catch fuel just in case. Also have 3 fire extinguishers ready. Learned from my first mistake. :-)

Anyway, what's the best way disable ignition? Thanks in advance?

Mrmerlin

OK this answers a lot of questions

So please answer these
what was the cause of the engine bay fire.
Has the engine ever run for you while you owned this machine?
have the knock crank and hall sensors been replaced?
did you squirt ether into the intake to see if it will run?

Saintrey

Yes the engine ran for me but wouldn't pass smog (too rich) so I changed the fuel injectors and that's when it caught on fire. I believe there was a fuel leak on one of the rails that caused the fire. I probably didnt tightened it enough.

Yes both knock and crank sensors are all new when I rebuilt the entire intake system.

I did the starter fluid into the intake and it ran.