Trying to get to the bottom of my non-starting issue (1999 996). I'm starting to think that I may have an issue with my fuel pump (fuse/relay?). The car started & ran perfectly... then for no reason it only cranks & cranks when I try starting it. I read a BUNCH of threads on this site... and it seems like I have a fuel issue. I'm going to check the fuse & relay. But I read where someone else said they turned the key, and heard their fuel pump priming... I hear nothing when I turn my key. Never paid attention before to if the fuel pump makes noise when turning the key to the 1st position. I KNOW the older (70-80's) POrsche feel pumps would make a NOTICEABLE sound when turning the key to the first position. How about my 1999 996? Should I hear it when in the first position? BIG THANKS so far for all the help I've been getting on this site! ;o)

 

Update: When I turn my key to the 1st position I hear no fuel pump.
I did the jumper-wire bypass to the relay (after it was removed). With
the bypass wire in place I definitely hear the fuel pump now when I turn
the key to the 1st position. I ordered a new relay. I'll give a update as
soon as I install the new relay.

 

Oz: Looks like you might have found your problem...and, yes, you should be able to hear your fuel pump priming on first key position. Not an obtrusive sound but should hear it.

 

OK... the BIG mystery! I bypassed the fuel pump relay (with home-made wire) just like shown to do, on Rennlist (I think that's where I saw it).
I get a "buzzing" of the fuel pump. It is definitely on. Try to start the car & nothing.
Just cranking & cranking.
Then put in a brand new Porsche fuel pump relay (in case my old one was bad) and DON'T hear the "buzzing" of the pump when the key is turned
to that 1st position!

NOW... something strange I noticed with my car also. And not sure if it has anything to do with the car NOT starting/ turning over. BUT... the
passenger door WILL NOT lock. So I'm thinking maybe the cars alarm/immobilizer won't allow it to start up?

Has anyone experienced a car NOT wanting to start when a door lock is NOT locking? Seems pretty drastic to stop a car from starting just because
a door lock won't work.

Thanks much!!! ;o)
Nick

 

If the alarm/immobilizer was the problem the engine would not crank.

A trick senior techs play on new techs is to remove the RFID pill from the key. The new tech goes to start the engine and it doesn't crank because the RFID pill is not present to provide its ID when "asked".

The new tech goes to the senior tech who has the RFID pill hidden in the forefinger of his glove and of course the senior tech turns the key and the engine cranks and fires right up.

The engine cranks so the problem is probably fuel or spark related.

While you have reasonable confidence the engine is getting fuel the DME might not be triggering fuel injector pulses. This can be due to a bad crankshaft position sensor. If this doesn't work the DME doesn't know when to trigger fuel injector pulses (and when to trigger spark either).

Another problem is -- not sure if a Porsche can fall prey to this but I came upon a VW that manifested this problem -- is while the battery may be healthy enough to crank the engine it doesn't supply enough power to work the coils. (Well, coil in the case of this VW.) A coil generates a spark when power is shut off to the coil which then has an electrical field collapsing. If the power to the coil is below a certain voltage the collapsing electrical field is too weak to generate the spark pulse as the electrical field collapses. IIRC with the VW it needed around 9 volts. I suspect the Porsche coils could require more than 9 volts to work properly.

 

The logic's with most ECM controlled engines, while cranking and you have a dash tachometer, you should see rpm's, if you have a bad CPS crank position sensor, you won't see rpm's while cranking. I've seen a few CPS bad with no fault codes.

 

Well.... After grabbing a fuel pressure gauge and testing at the fuel rail... I'm getting a zero reading on the gauge after cranking for a few seconds. Zero.
Next, I was onto taking the fuel pressure down at the fuel filter... as I knew that there is actual gas coming out of the filter (when cranking). I hooked up the fuel pressure gauge at filter and also received a zero pressure reading. Even though I could remove the gauges fuel line attachment and immediately I'd get gas coming out of the hose when cranking the engine. Seemed like not much pressure though... but EASILY enough gas coming out of the hose that you'd have a difficult time drinking it all, if it were say a beer... LOL. Also I can very easily block gas from coming out of my fuel filter by simply placing my finger over the hose. Not much pressure.
So... next on the agenda seems to be purchasing a new fuel pump.

 

Working from memory the fuel pressure reading should be around 55psi with the engine off. I don't think you could easily halt fuel flow at that pressure.

While the fuel pump may be running -- or at least humming -- a fuel line may be split/cracked and allowing fuel pressure to bleed away.

 

What Macster says, you might even pop the fuel fill cap and listen for fuel splashing in the tank from a leaking pressure line.