starting problem

[john944]

i have a early 85 porsche 944 n/a it starts and dies two seconds later. i have replaced fuel pump, fuel pressure regulater, dme relay and mass air flow. the timing is right and it is gettin fire. if i spray starer fluid in the throttle body i can keep it running. i would b greatful for any advice to help fix my problem

[mikepellegrini]

I dunno. I'd check the fuel pressure. Test for fuel delivery: Fuel Pump Delivery Rate Checking

If you have a new pump and new FPR, the only things left would be a clogged filter or a clogged strainer (on the bottom of the tank).

I'd still do the fuel pressure/delivery test just to confirm there is no/insufficient pressure.

The strainer is easy to access - it's right on the bottom of the tank. Fuel Pump Suction Strainer - Removing, Cleaning, and Replacing

If that checks out okay, then it's gotta be the fuel filter.

[john944]

thanks buddy, i didnt even think about that at all. guess its one of those if u dont see it you dont think its there lol,ill give it a shot first thin in the morning and get back with you

[john944]

the straier doesnt apear to have any dirt in it at all. its very clean, so now im back to wondering whats causing my car to not run

[john944]

o and i have alreadu put a new fuel filter on the car

[mikepellegrini]

If that's the case, can you confirm that the pump is actually running?

You should try checking the pressure - Fuel Pressure - Checking

Here's the procedure for testing the DME relay: DME Relay Information and Testing

[john944]

the fuel pump is running and its gettin enough pressure, i think somethin is shuttin my fuel injectors off but im not for sure

[mikepellegrini]

The injectors are noisy in these cars. If they're firing, you'll hear the clicking.

[john944]

i pulled the fuel rail plus the injectors out of the intake, they are working when i crank the engine over. now everything just dont make since, is it possible its a fly wheel sensor?

[mikepellegrini]

Not if you have spark.

I still think you oughta check the fuel pressure.

[john944]

my fuel pressure is at 35 psi. book called for 33 - 39. so im right where i need to b. but still isnt stayin running after start

[nynor]

big vacuum leak.

[carsontc]

^^^ what he said

[john944]

iv replaced all hoses and j pipe under the intake all all other t's, still just starts and dies.

[nynor]

you got something loose or forgotten. i am betting the large hose that is directly under the middle of the intake manifold. you need to go over the entire thing, including the gaskets where the intake meets the cylinder head and the intake boot. the possibilities for a LARGE vacuum leak are not innumerable, but there are many.

or

the AFM is bad. but i think you stated you replaced that item.

[john944]

yea iv already replaced it. and about a month ago i put new intake and exhaust gaskets on this car. i know it isnt a leak cause if u sprayed car and choke cleaner in any leak the engine would run, if there is one. but i will keep trtying the vaccum theroy. i agree, something might not b sealing or sealing all the way

[mr5296]

do you have an aftermarket or high flow filter on, cause mine was doing that and i found out that right behind the maf, the filter wasnt seated correctly and there was 1/8" gap.

[Slam]

Three checks in addition to looking for vac leak: DME temp sensor, stuck AAV (auxiliary air valve), O2 sensor. These three things will affect cold starts if they're not behaving themselves. If you can start it and keep it running on the throttle, I'm guessing the AAV is stuck - closed probably.

These issues are annoying, aren't they?

[nynor]

Originally Posted by john944

yea iv already replaced it. and about a month ago i put new intake and exhaust gaskets on this car. i know it isnt a leak cause if u sprayed car and choke cleaner in any leak the engine would run, if there is one. but i will keep trtying the vaccum theroy. i agree, something might not b sealing or sealing all the way

you have it somewhat backwards. if it were a small leak, spraying starter fluid into the vacuum leak would make a running car have higher RPM's.

if the vacuum leak is so big the car won't run, you need to add more fuel to make up for the leak. spraying starter fluid directly into the intake is adding more fuel to make up for the leak.

d.

[john944]

well i found some what of the problem. seems someone has it in for me, the pored sand in my gas tank.... so after i got all of that cleaned now im not gettin a spark, im gettin signal from computer, now its the coil is bad. lol