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Old 01-02-2017, 08:57 AM   #1
firstRWD
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Weird Fuel Pump Issue

Long story short, I had the classic "bang on fuel pump, car starts" issue. I replaced the pump, but it didn't fix the issue. I thought maybe I got a bad pump, so I got another one. Same issue. It's actually becoming worse. I'll have to keep knocking on the pump with a hammer every time I start the car. Often I'll have to keep hitting it for a while before it'll keep going or the car will die. It's randomly died on me while driving. I knock on the pump while cranking the engine and it'll start back up. I tested the wire connection from the pump to the outside of the pump hanger(whatever that's called) and it's good. The connector on the top of the pump hanger seems good and seems like it's making a good connection. Any ideas?

I also have a hard start issue, a rough low idle issue, and a ~4,000rpm bad stumble that I'm trying to figure out. I don't know that any of that is related, but just mentioning in case it is. I have good fuel pressure when the car is running.
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Old 01-02-2017, 10:51 AM   #2
ahlem
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Fuel filter? What did you replace the pump with? Also check the Fuel pressure regulator and take a fuel pressure test. Clean the electrical terminals at the fuel pump. Is this a late model with one fuel pump?
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Old 01-02-2017, 11:27 AM   #3
MrBurgundy
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I'd start off by checking the relay for the fuel pump. As for the hard start, idle, stumble thing, I'd start off by checking the main relay and CPS sensor. Make sure the cps wiring has some slack.
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Old 01-02-2017, 11:31 AM   #4
firstRWD
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It's a 90, one pump. Would fuel filter issues be affected by knocking on the fuel pump hanger? Same question for FPR?(which is also new). The new pump is from autozone. The pump that was in it is a Bosch. They both act the same. As I said, I have good pressure and the connecter looks good.

How do you do a check on a relay? The CPS was replaced a few months ago, so it should be good. I'll check the wire routing, though.
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Old 01-02-2017, 01:11 PM   #5
CMatos
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Quote:
Originally Posted by firstRWD View Post
It's a 90, one pump. Would fuel filter issues be affected by knocking on the fuel pump hanger? Same question for FPR?(which is also new). The new pump is from autozone. The pump that was in it is a Bosch. They both act the same. As I said, I have good pressure and the connecter looks good.

How do you do a check on a relay? The CPS was replaced a few months ago, so it should be good. I'll check the wire routing, though.
Just pull the relay out and jump the terminals to feed power directly to the pump just to make sure it's operating correctly. I don't have my Bentley in front of me right now, but I believe it's terminals 30 & 87. Just verify yourself before doing it.
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Old 01-06-2017, 05:40 PM   #6
bblazen
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I too am having a similar issue... I'm getting 42-45 psi at the rail but have fuel cutoff at 4K-4.5k newish fuel pump. And sometimes when I toggle the key while driving it will go to redline... ��
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