Chasing my tail!

[87GN87GN]

Have a stock 87 GN with 90,000 miles. Car was running fine but then intermittently started falling on its face around 3000RPM and just not making power. Turbo will make a little boost but engine will not get over 3200RPM and engine makes some low popping sounds as it stumbles and dies. Now the problem is there constantly. The fuel pump was replaced with a new stock pump a few months ago and have put at least 500 miles on car since it went it. Since chasing this problem have replaced ECM, chip, MAF, coil and ignition module and no change.

Finally hooked up a fuel pressure gauge and when key turned half way pump comes on and gets to 40 psi but dies off to 10 psi in a few seconds. With car started at idle getting steady 30 psi. When revved to 2000-3000 RPM gets to around 45psi then drops back to 30 at idle. While at idle pulled fuel pressure regulator vacuum line and pressure jumped to around 40.

The rapid loss of pressure when key turned half way and steady low 30 psi at idle makes me think the fuel pressure regulator is bad. Am I on the right track or are there other things I should be considering??

 

[No disintegrations]

You should keep this all in one thread so we can refer to stuff already discussed.

I think it's majorly hurt or.... What's it look like in the air filter box? Check for something that blocks most of the airflow to the air filter. Or a horribly clogged air filter. Can you see light through it with a flashlight?

 

[Chuck Leeper]

Or a horribly clogged air filter. Can you see light through it with a flashlight?

What does this have to do w/ fuel psi??

Could well be the fuel feed hose from the pump to the hanger is either loose, split open, or is not efi hose, and has disintegrated.
Pump hot wired?
Volts at the pump? Ground wiring good?
Filter fresh?
Adj regulator? If not, suggest you get 1.
Any other monitoring devices, such as Scanmaster, gauges, etc?
Injs clean? If not, could be the psi loss is leaky injs dumping into the engine.
Have you done a "spring cleaning"? Sounds like you are throwing parts at it....Gonna get expensive, REALLY quick.
NE1 around you that has experience w/ these cars?

 

[87GN87GN]

What does this have to do w/ fuel psi??

Could well be the fuel feed hose from the pump to the hanger is either loose, split open, or is not efi hose, and has disintegrated.
Pump hot wired?
Volts at the pump? Ground wiring good?
Filter fresh?
Adj regulator? If not, suggest you get 1.
Any other monitoring devices, such as Scanmaster, gauges, etc?
Injs clean? If not, could be the psi loss is leaky injs dumping into the engine.
Have you done a "spring cleaning"? Sounds like you are throwing parts at it....Gonna get expensive, REALLY quick.
NE1 around you that has experience w/ these cars?

Yes, throwing parts and $$ at it and I know that is an expensive "plan" if you can even call it that. I am a new GN owner and have been reading everything I possibly can about the cars on this forum and other places but this is a new beast to me. Lots of Buick experience but with big block 68-70 Gran Sports but this is first GN. I live in northern San Deigo County (Poway area) so if anyone is in the area who might be able to assist that would be awesome.

Fuel filter is new, ground to pump has been checked several times, air filter and air intake plumbing has been check and there is no blockage, running a test pipe so there is no cat converter blockage either. Scanmaster going in within 48 hours and will post data once I get some.

Adjustable fuel pressure regulator is on the way from G Body, have hotwire kit and I know I need to get that installed like now.

With such a rapid loss of pressure when key turned half way, if it were the injectors leaking wouldn't the oil smell strongly like gas? It goes from 40 psi to 10 psi in seconds and I can't imagine the injectors can leak down that quickly? Thanks as always, this is a great forum.

 

[No disintegrations]

What does this have to do w/ fuel psi??

Could well be the fuel feed hose from the pump to the hanger is either loose, split open, or is not efi hose, and has disintegrated.
Pump hot wired?
Volts at the pump? Ground wiring good?
Filter fresh?
Adj regulator? If not, suggest you get 1.
Any other monitoring devices, such as Scanmaster, gauges, etc?
Injs clean? If not, could be the psi loss is leaky injs dumping into the engine.
Have you done a "spring cleaning"? Sounds like you are throwing parts at it....Gonna get expensive, REALLY quick.
NE1 around you that has experience w/ these cars?

My air box comment has nothing to do with fuel press. I was trying to think of things that will make a car not go over 50 mph. LOL. ( from op earlier thread) 40 psi seems like enough to at least go 75. haha. with dash mounted gauge it could be dropping more at high demand and I realize that too.

But the press bleed down could be loose hose at the pump hanger in the tank.

Can you put a temporary fuel press gauge on the windshield so you can see while driving? should rise 1 to 1 for each pound of boost yada yada. 43 base + 15 boost = 58 psi fuel press ( I think we all know this but has to be said)

 

[TexasT]

With it loosing pressure wouldn't worry about that if the car starts and runs. I would worry what you put in there and call a "stock" pump. Sounds like it is a low volume piece that can not keep up with the needs of the engine.
I would seriously consider a larger pump when going in with the hotwire kit. You need a sizable amount of fuel to make power in one of these and it needs to keep up as the boost comes up or you will have bigger probs than it wont rev.

 

[dynoman]

I agree with Chuck and TexasT on either loose/cracked internal hose or bad pump , but your going to have to drop the tank either way . While it's down check all connections at the top of the tank and at pump.

 

[larrym]

Did you replace the rubber hose at the pump when the pump was replaced? Could be burst or a loose clamp at the pump.

 

[Gene Van Horn]

I dont know where you are in maryland, if not to far shoot up 95 to Jim Dunn rite when you get i to philly.

 

[turbofrank]

He is in California u in need to hit search tool and invest in scan tool.

 

[TexasT]

It happens. Drop the tank and check it out. I bet it has something to do with the rubber connector.

 

[John Larkin]

If the hose is split or loose it won't make fuel pressure much. The pump pressure will find the path of least resistance. BTDT. I had a split hose once. Car basically wouldn't run.

 

[87GN87GN]

Thanks for all the info guys. TexasT, appreciate the picture too, I definitley understand the concerns with the rubber connector hose in the fuel pump assembly. Wallbro pump and adjustable fuel pressure regulator on the way from G Body. Once I get parts installed I will send an update.