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Discussion Starter #1
My 2008 GXP stick with 31,000 miles went to reduced power with check engine symbol and "reduced power" showing on DIC.

It shows a P0087 code indicating low pressure at the fuel pressure sender.

Most likely the HPFP going out?

Or bad fuel pressure sensor?

Does the pump ticking change with bad pump?

The fuel pump is easily found GM part #12646884 superceded by #12658478 around $275 to $325 from GM parts suppliers online.

Is the GM pump the one to get or some of the lower priced pumps available from Auto Parts stores or Amazon better or crap.

Also anybody know which fuel line has to be replaced at the same time and part number?
 

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Sounds like its your in-tank fuel pump...
 

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Discussion Starter #3
How would I determine if it is the in tank fuel pump?

I forgot to mention that it runs really rough when I start it.
 

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There is a service port on the fuel rail that a pressure gauge can be connected to after the pressure has been bled from the system.
 

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Discussion Starter #5
Sounds like its your in-tank fuel pump...
Most of the posts regarding p0087 indicates HPFP failure.

I'm curious why you indicate the pump in the tank is the culprit?

Any way to verify the in tank pump failure.
 

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Discussion Starter #6
There is a service port on the fuel rail that a pressure gauge can be connected to after the pressure has been bled from the system.
You're referring to the port with Schrader valve? Any idea what the reading should be? And if low - bad HPFP? Or in tank fuel pump?
 

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I didn't read deep enough into the procedure to see exactly whare the test ports are, but there are two of them, one before and one after the HPFP. There are also lots of warnings about de-pressurizing the fuel system and containing leaking/spraying fuel. The first step in diagnosing a P0087 is to confirm that the in-tank pump is supplying the HPFP at 57-67 psi pressure. If that pressure is low, the in-tank fuel pump is likely to be the problem. If it is correct, the problem is either the HPFP or worn camshaft lobes.
 

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Discussion Starter #8
I didn't read deep enough into the procedure to see exactly whare the test ports are, but there are two of them, one before and one after the HPFP. There are also lots of warnings about de-pressurizing the fuel system and containing leaking/spraying fuel. The first step in diagnosing a P0087 is to confirm that the in-tank pump is supplying the HPFP at 57-67 psi pressure. If that pressure is low, the in-tank fuel pump is likely to be the problem. If it is correct, the problem is either the HPFP or worn camshaft lobes.
Thanks John,

If I install the fuel pressure gauge at the test port upstream of the HPFP, it should tell me if the in tank pump is working?

If pressure is 57 to 67 upstream, then the HPFP is tested by inserting tester at the downstream port?

I have a manual coming from Helminc but won't be here for a few days.

I need to clean the HPFP electrical connection too. It was mentioned on another post re p0087
 

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That's the way it reads. If you have the proper pressure upstream of the HPFP, the next step is to remove it.

Check all of the connections to the in-tank pump also. Other things mentioned are a skewed fuel pressure sensor and faulty fuel injectors.
 

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Discussion Starter #10
IThe first step in diagnosing a P0087 is to confirm that the in-tank pump is supplying the HPFP at 57-67 psi pressure. If that pressure is low, the in-tank fuel pump is likely to be the problem. If it is correct, the problem is either the HPFP or worn camshaft lobes.
Thanks for the tip John,

Fuel pressure at the inlet to the HPFP is 60# so the intank pump is good. The electrical connection to the HPFP is clean.

Time to replace the HPFP.
 

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Discussion Starter #12
The dealer quoted $850 for pump and install.

The pump is $280, fuel line $36 and pump install gauge is $70. Less than $400.

I ordered everything online.
 

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Discussion Starter #14
Installed the new HPFP and pipe yesterday. It took about 2 hours and the process was not difficult.

The GM shop manual did not mention anything about the use of the EN48896 installation gauge that ensure that the camshaft lobe is in the base circle position. At base circle the tool will be flush with the head

Car is back to running normal - no more check engine light and reduced power.

Thanks JohnWR for the advice and ghost for the instructions that mentioned using the EN48896 tool.

Anybody knows what goes out in the HPFP? Pump or solenoid?
 

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That is great news. Glad you got it fixed.

I believe that there are two main failure modes. Pump failure that leaks fuel into the oil, and regulator failure that just results in low pressure.
 

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Discussion Starter #16
I did not have fuel on the engine side so mine must have had a regulator failure.
 
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