another non-starting 944

[derek924s]

I have an 88 924S. I have been rebuilding it for about 6 years after an accident. It started right after that accident so I know thats not the cause of it not starting. It is getting spark to all plugs, the cylinder compression is good, fuel pressure is normal, fuel is getting to the rail, i soaked the injectors and put new seals on them, replaced the fuel pressure regulator , the battery, and the dme control unit. I am lost! the engine cranks over (with no unusual sounds) but will not start. Also the tack bounces when I turn the engine over so I am pretty sure its not the speed or reference sensor, right? It is obviousley getting spark, and fuel to the rail so would it be safe to say that the injectors are not firing. Is there a way to physically see if they are firing or can I only do a voltage test? If they aren't firing then is it most likely the ecu/cpu?

[Eldorado]

check for vacuum leaks... could also be a bad AFS.

[derek924s]

i'll check them tomorow and get back to you. whats afs?

[Eldorado]

air flow sensor, between the big rubber jboot and air filter.
check the plug on there.

[mjadair]

Soaking an injector won't really work, the cleaner must flow through. There is a place to send them to have them ultrasonically cleaned. Incidentally, did you remove all of the old gas from the tank?

[fliphkd7]

rc engineering has a great reputation for cleaning injectors. www.rceng.com

[onZedge]

Let's get these things out of the way first:

Why and when did you change the DME? Did you try jumpering out or swapping out the DME/Fuel Pump Relay? Did you reconnect the injector wire harness? When was the fuel filter last changed? Did you double check the spark plug wire firing order? What did you soak the fuel injectors in? Did you drain the old and put in fresh gas like mjadair suggested?

If you don't have an injector noid light, you can pull the fuel rail off with the injectors on and crank it to see if they are squirting. Should have an aerosol, not a stream or dribble.

I just noticed that this thread was started 2 weeks ago. Did you get it running yet?

[Porsche-O-Phile]

Fuel, air spark.

You're getting pressure to the rail, but are you actually getting fuel to the cylinders? Crank it a bit, then pull a plug and see if the cylinder smells like gas. Or pull the rail and crank with cups under the injectors to see if they spray.

For air, you're saying you have good compression - obvious stuff like filters checked? Valves opening & closing properly (you can view through the holes where the intake runners go if you pull it and rotate the engine slowly by hand.

Spark - check the order of the plugs, especially on the distributor cap. Put the engine at TDC by the timing mark, pull the cap and make sure the rotor inside is pointing to the #1 wire. You'd be surprised how easy it is to screw it up.

[TibetanT]

Ah...those pesky 944's not starting again, huh?

Okay, enough with the jokes.

As everyone else has mentioned here above, make sure the fundamentals are covered first. Spark, gas, etc., etc..

Next, in the engine compartment, check that the reference and speed sensor connectors are not loose. Ask me how I know this? I missed it all of three months worth of ca$h being spent on other "suspect" components.

The DME/ECU brain sends a signal to the fuel injectors after it gets its "okay to run" from the oxygen sensor and AMF.

Also, seems silly to ask this question but have you tried loosening the BIG hose going to the throttle control housing and spraying some starter fluid into it to prime your engine to fire?

Of course, I am speaking from experience with a 1987 944 so I do hope this helps you. If not, and you have a question with regard to other components related, I have the entire set of Porsche Factory manuals, so would be willing to help answer routing and other wiring questions as need be.

Good luck with this !

Let us know if/when your running.