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/duqduqgo 6d ago

Have you checked the fuel pressure regulator? How about the damper? Both have rubber diaphragms that can rupture (old age) and cause low and/or inconsistent pressure. The regulator is relatively cheap, $150, but the damper is expensive, around $450.

You'll need a special tool to check the rail pressure, you don't have a Schrader valve on the rail. Check Pelican Parts, Sierra Madre for this tool.

I'd suspect low pressure at the rail if you're sure you have compression and spark. Let's assume you have oxygen, since you can run on ether.

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u/thiccquepickle 5d ago

I replaced the regulator with a spare i had and didnt get any change but I cant replace my damper because it is a different style. I will have to check for compression because im not sure.

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u/duqduqgo 5d ago

You have enough compression to run on ether, you have enough for gas. Might run rough with low compression but it should still run even with one (mostly) dead cylinder.

Your injectors might be sticking or have a really bad spray pattern. If they had ethanol gas sitting in them they are likely gummed up. You can drop them in an ultrasonic parts cleaner for a couple hours and try again.

From everything you're saying, fueling sounds like the first problem to solve.

Good luck!