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Engine has low compression

 
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Judge  



Joined: 22 Mar 2024
Posts: 19
Location: France

PostPosted: Mon Apr 07, 2025 3:01 am    Post subject: Engine has low compression Reply with quote

Hello guys,

After a year working on my car, I fixed pretty much everything, even rebuilt the K-Jetronic successfully.

Since the engine keep not starting, I finally did a compression test.

All cylinders are around 75psi.

I don't know where to go from here. There's no oil in the coolant, so it's probably not the head gasket from my pov.

What do I do guys?
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Judge  



Joined: 22 Mar 2024
Posts: 19
Location: France

PostPosted: Mon Apr 07, 2025 5:56 am    Post subject: Reply with quote

MISTAKES WERE MADE

I had the throttle closed when I did the compression test. I did it again after putting some oil on top of the cylinders. I did the test again with the throttle open, and I got 125psi.

I tried starting it, and it didn't start, although it had some smoke coming out of the intake manifold, but it didn't smell like burned fuel.

I am not 100% of the timing of the engine. I put the flywheel at TDC, spinned it clock wise 10 degrees to see the mark on the flywheel, and set the distributor rotor aimed at the cylinder 1's sparkplug.
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pierro  



Joined: 15 Nov 2016
Posts: 16
Location: France

PostPosted: Mon Apr 07, 2025 4:31 pm    Post subject: Reply with quote

If you have a stroboscoop to check the exact timing of your engine, that would be a prerequisite.
After that i would focus on the fuel injection.
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924RACR  



Joined: 29 Jul 2001
Posts: 9060
Location: Royal Oak, MI, USA

PostPosted: Mon Apr 07, 2025 10:01 pm    Post subject: Reply with quote

More information would be helpful - what year and model is your car? NA or Turbo?

For distributor alignment... at TDC the distributor rotor also wants to point at the last bolt on the intake manifold, and then the distributor itself must be aligned to starting settings - these are noted in the manuals, do you have any service manual (factory or Haynes)?

Have you verified that you are getting a spark from any of the leads while cranking the engine?

Have you confirmed that the timing of the cam is correct relative to the crankshaft?
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barnwerks  



Joined: 28 Oct 2022
Posts: 40
Location: Northeast and southeast US

PostPosted: Tue Apr 08, 2025 7:29 am    Post subject: Reply with quote

Remember that the crankshaft has two TDC's. One at compression and one at exhaust.
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