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924 fuel pump

I am working on a 1977 924 that had set for 25 years, I have replaced fuel pump,lines & injectors.Engine is hard starting. My question, is the fuel pump suppose to run when key is in run position,or only when cranking .thanks

Old 10-21-2019, 10:29 AM
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Here's a good website for the early 924 owner.

Porsche 924 Garage & Register home
Old 10-21-2019, 10:36 AM
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I can hear mine when I turn the key, just before it cranks. I'm also using a Focus9 Fuel DME...
Old 10-21-2019, 11:56 AM
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Quote:
Originally Posted by Grounder View Post
I am working on a 1977 924 that had set for 25 years, I have replaced fuel pump,lines & injectors.Engine is hard starting. My question, is the fuel pump suppose to run when key is in run position,or only when cranking .thanks
No, there is a sensor on the air meter plate that senses movement. Pump only runs when cranking. Not before. I often wondered if a 928 CIS fuel relay would be a good upgrade. It runs the pump for a few seconds every time its energized.
Old 10-22-2019, 10:50 AM
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Early 924 pump should run for a couple of seconds to prime the CIS system. The early relays are near impossible to find. Go to 924board.org and do some searching on early 924 relay, as I can't recall from memory the part numbers and such.

If the car is hard starting, it's more likely that the warmup regulator needs to be rebuilt / replaced, AND/OR that the thermo-time valve + cold start valve are not functioning correctly.

If you search in the How-To section of 924board, I have a complete writeup on using a Hoffman CIS pressure tester that explains the diagnostic procedure directly distilled from the Bosch CIS book (something I strongly recommend that you add to your library).

The Focus9 DME relay referenced above is for a 1987-88 924S that has the 944 engine and DME. The early cars do not have this setup, so that will not work for the '77 mentioned by the OP.
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Old 10-31-2019, 07:43 AM
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Lots of good stuff on CIS in the 911 section too. As Ideola states, spending $90 on a good quality (not HF) CIS-specific fuel pressure tester is THE best thing you can do. John

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