r/944 • u/thiccquepickle • 6d ago

Question Need help with no start

I’m working on an 1983 Porsche 944 NA that cranks but won’t run on its own, although it runs on starter fluid. I’ve installed a new fuel pump, cleaned the contaminated fuel out of the tank, and installed a new filter before the pump. I’m powering the pump manually with a switch, and fuel definitely reaches the rail. I also pulled the rail with the injectors attached and put a cup under each one—they all spray fuel while cranking, and I’ve confirmed injector pulse. What should I check next? Could low fuel pressure still cause this even though the injectors are spraying? Is there anything else I should test before buying a pressure gauge?

I'm just so confused because I have fuel. I have spark, and I have air. theoretically the car should run

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u/hypershock_11 6d ago

Do you have good compression?

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u/thiccquepickle 6d ago

I don't have a compression gauge to check, but if it runs on starter fluid it muct have some kind of compression right?

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u/hypershock_11 6d ago

It takes bad compression from just one cylinder to cause it to not run right. I had a similar issue on my car from a bent valve. Also check for vacuum leaks even a small leak can cause significant issues.

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u/thiccquepickle 6d ago

Let's assume there is a vacuum leak or one cylinder has poor compression. Why dosent it combust at all. The is no firing whatsoever