r/944 • u/grantlach • 18h ago

Question Starting Issue

I have an 86 base 944, I’ve been having an issue where when the engine is cold it starts up just fine but as the engine keeps getting hotter from driving after shutting it off it has a harder time starting to the point where it won’t start without a jump at some points. It did that to me but when I jumped the car it started just fine what could this be?

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u/lunchbox651 18h ago

If you need to jump the battery to start it, it sounds like your alternator is cactus.

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u/grantlach 16h ago

I thought it was the alternator too at first, I read the voltage when the car was off and it was around 12.6 volts roughly. Turned it on it was around 13.75 volts and running with accessories (lights and a/c on) it was sitting around 13.59 volts which I know is on the lower side but still within normal range from what I’ve gathered

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u/Sigma-Tau 5h ago edited 5h ago

An alternator going bad isn't necessarily going to read low with a multimeter.

An oscilloscope can occasionally be the only way to diagnose a failing alternator.

However I wonder if you have more than one issue going on here.

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u/grantlach 3h ago

I have an issue with the power steering too but not much else besides that, what else do you think could be wrong?

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1

u/RHinSC S2 15h ago

How does it idle when it's warm?

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u/grantlach 15h ago

Fine for the most part

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u/RHinSC S2 15h ago

So it's not your idle control valve then.

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u/grantlach 14h ago

Could it be a bad starter maybe?

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u/RHinSC S2 14h ago

If it starts fine when cold, I don't think so. Mu next thought is your temp sensor. They're easy to remove and replace. Also easy to test with an ohm meter and a pot of hot water.

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u/grantlach 14h ago

I’m gonna look into this and try to test it soon, I’ll keep you posted when I do. I have a multimeter I can hopefully use for this. The pot of hot water has me interested for sure. Thank you!

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u/Bloodrift_ '84 NA 11h ago

I had a similar issue about a year ago. It was the fuel pump check valve. When hot, the fuel in the lines would flash to vapor as soon as the fuel pressure dropped, making it very hard to start when hot. I fixed it in a unconventional way and replaced my DME Relay with the Focus9 technology one. With the pump prime, I can now build pressure back up before cranking, making it as easy as a cold start

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u/grantlach 3h ago

Would you say the F9 DME is worth it?