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Old 09-16-2016, 05:23 PM   #1
Buckwsr
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2000 Silhouette Fuel Pressure questions

Hi. I have a 2000 Silhouette with the 3.4L V6...just like they all have! Ha!
Almost 160,000 miles....
I am wondering if anyone knows what should be the recommended fuel pressure when measured at the schrader valve on the fuel rail?
I have long suspected my fuel pump was not putting out enough pressure.
Key-on-engine-off gives me 25psi of pressure. Start the engine, and it goes up to 32psi. Lately I've had a few instances where the car wouldn't start....just crank and not fire up. A few hours later, try again, and it started. This has happened twice in the last month. Once started, the engine seems to run fine.
Another question, once the engine is shut off, how long should it take for the fuel pressure to drop back down to 0 psi? Does 20 minutes or so sound about right?
Another thing is a DTC P0171 lean fuel mixture on bank 1. This has been off and on, but mostly on, for a couple years...like back to when I had this fuel pump installed... I'm wondering if an insufficient fuel pressure could cause that DTC? I know there are other possible causes....
Thanks, Buckwsr
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Old 09-17-2016, 07:10 AM   #2
gmtech1
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Re: 2000 Silhouette Fuel Pressure questions

Quote:
Originally Posted by Buckwsr View Post
Hi. I have a 2000 Silhouette with the 3.4L V6...just like they all have! Ha!
Almost 160,000 miles....
I am wondering if anyone knows what should be the recommended fuel pressure when measured at the schrader valve on the fuel rail?
I have long suspected my fuel pump was not putting out enough pressure.
Key-on-engine-off gives me 25psi of pressure. Start the engine, and it goes up to 32psi. Lately I've had a few instances where the car wouldn't start....just crank and not fire up. A few hours later, try again, and it started. This has happened twice in the last month. Once started, the engine seems to run fine.
Another question, once the engine is shut off, how long should it take for the fuel pressure to drop back down to 0 psi? Does 20 minutes or so sound about right?
Another thing is a DTC P0171 lean fuel mixture on bank 1. This has been off and on, but mostly on, for a couple years...like back to when I had this fuel pump installed... I'm wondering if an insufficient fuel pressure could cause that DTC? I know there are other possible causes....
Thanks, Buckwsr
Key on engine off should be 52-59psi...fuel pressure could cause the p0171...at least 20 min on the bleed down.
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Old 09-17-2016, 07:19 AM   #3
CarloITA
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Re: 2000 Silhouette Fuel Pressure questions

I found a document for you, but you may want to test the pressure regulator first.
(here is a video, there are many like that)
https://www.youtube.com/watch?v=aITQclp7zIE

I can't attach the document because it is too big, you can find it here
http://www.askatech.com/AskATechLive...Track/G083.pdf

have fun and good luck
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Old 09-19-2016, 10:06 AM   #4
Buckwsr
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Re: 2000 Silhouette Fuel Pressure questions

Thanks for the replies and help. It seems kind of distressing that my resting fuel pressure would be less than half the recommended psi. I replaced the fuel filter two years ago, and will probably do it again now, but I do not suspect that to be the problem. Regarding the pressure regulator, I recall replacing that as well, and may do so again, just to be safe. Nonetheless, there is no change in pressure when I remove the vacuum line from the regulator while engine is running. Seems to be a strong vacuum present at that point. There is no visible gas leakage at the regulator or vacuum line, so I do not suspect the regulator to be bad. I just think the fuel pump is not getting the job done....
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Old 09-20-2016, 10:48 PM   #5
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Re: 2000 Silhouette Fuel Pressure questions

The correct way to test the regulator is to block the return line.......then cycle the key on to off several times(10 seconds in between), to get max pressure......if pressure stays low, you need a pump(change fuel filter first before doing this test).....

If you have rubber fuel hoses, the return can be clamped with a rag and vice grips....

If you have plastic lines, then you need a special tool....a shut off valve that is designed to be inserted into the return line....
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