Fuel Pressure

fuel pressure should be 55-60 psi look for a clogged fuel filter first. it should hold that for 5 minutes after car shut off.otherwise may be the pump. also clean the throttle plate on both sides with choke cleaner and iac hole.

what is the fuel pressure supposed to be.my tested at 25lbs?

Pressure 52-59 psi
KOEO Key on Engine Off

Here is a guide to help you

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please let us know if you need anything else to get the problem fixed.

2002 Pontiac Grand Prix V6-3.8L SC VIN 1
Pressure 48-54 psi
KOEO Key on Engine Off

2002 Pontiac Grand Prix V6-3.1L VIN J
Pressure 52-59 psi
KOEO Key on Engine Off

For 2002, I'm showing the same pressure for both engines.

I see what the difference is........

It's the non-supercharged 3.8 (VIN K) that is 53 to 59, same as the 3.1. The supercharged version is a little lower.

I've been working on an issue with my car for some time already. I have dropped from getting 28mpg to 22 mpg. I am also getting codes for misfire and running rich. After a major tune up as well as a few other repairs (with no positive results), I have just found out my fuel pressure is 43psi when the key is in the 'ON' position but then jumps up to 83psi after I start the car. When I take the vacuum line off from the Fuel Pressure Regulator while the car is running, there is no change in the fuel pressure or the performance of the car.
Does it seem like the problem is the Fuel Pressure Regulator or is there a problem elsewhere?

Check the fuel return line if its clogged-up if not replace the regulator then report back asap.

How would I check to see if the return line is clogged?

Disconnect the fuel return line on the fuel rail and apply air pressure to it, if not clogged-up replace the fuel pressure regulator

Do you know if there is a trick to disconnect the return line? I was trying to disconnect the line where the steel line end and changes back into rubber/plastic line. The rubber/plastic line slips over the steel line and it has 4 clips on the inside of the rubber/plastic line that clip onto the steel line. I can't seem to get all 4 clips pushed back at the same time in order to disconnect the line.

Do you have vacuum on the vacuum hose to the fuel pressure regulator?

Yes there is vacuum. When the car is running and I take the vacuum line off from the regulator, there is vacuum on the vacuum line. When I remove the line there is also no change in how the car runs. I still get the same amount of pressure on the fuel rail.

You probably need a special disconnect tool.

Note: When you remove the vac hose on the regulator the pressure should rise to about 8psi-sounds like the regulator

I changed out my FPR earlier today and to my surprise, and disappointment, it still didn't solve my problem. I really had high hopes that this would do the trick.

With the key turned to ON, I get closer to 48psi now compared to 43psi before I changed it. After I start the car I am getting 84psi compared to the 78psi to 84psi before I changed it. I also pulled off the vacuum line with the engine running and there was no change. I was able to position the pressure gauge so I can see it from inside the car. While the car was in gear but holding down the brake, I am able to rev the engine enough so that it bogs down. The fuel pressure is still above 80psi while the engine is bogging down.

I'm not exactly sure of the mechanics behind the supercharger but it also seems that the bogging happens whenever the supercharger is giving boost according to the dashboard gauge. Could part of the problem be that the engine is getting extra fuel because of the boost but not enough air to match and is therefore dumping in way too much fuel with out enough air to back it up? Like I said, I'm not sure of the mechanics behind the S/C but I'm grasping for straws. I still don't think this would explain the reason for such high fuel pressure.

Any suggestions would be greatly appreciated.

does this engine have a supercharger?

Yes it has a S/C. It's a 99 GTP.

this car runs on very high fuel pressure when hard accelerating. there is a resister located behind the passengers side headlight that reduces voltage to the pump when running at idle to reduce fuel pressure then when accelerator is pressed fast the fuel pump relay bypasses the resister and gives full power to the fuel pump which pushes 90 psi. this is normal. however it is not normal for 90 psi when at idle and running. does the fuel pressure stay at 90 at all times? even at idle when hot?

Shakes or Wobbles problem
1996 Pontiac Grand Prix 6 cyl Two Wheel Drive Automatic

i try to find the fuel pressure check port and cant find it the people at the shop said it was somewhere behind the engine but i cant find it i did find something on the passenger side engine look like it was at the end of the fuel rail but i wasnt sure it was under the power steering thing that you put you fluid in

When I checked it today, I checked it when it was cold after first starting and after the car warmed up and the idle slowed down to 800rpm. Both times the pressure was still around 84psi. Even when I put the car ingear and the rpm dropped another 100rpm, the pressure was still at 80psi.
Do you know exactly where the relay is and what it looks like?

Its on no.3 see pic

it would appear that the fuel pump speed relay may be stuck on.

I located the relay and I have attempted a few things to see if I would get any changes in the pressure.
1. I swapped the fuel pump relay with the fuel pump speed relay since they are the same part and there was no change in pressure.
2. I opened up the relay so I could bench test the relay to make sure it would switch between the 2 possible positions. It worked as it should.
3. I reinstalled it in the car while the cover was still off. I manually switched the relay while the car was running and the pressure went from 84psi while it was idling to 93psi-95psi when I forced the relay to the other position. I'm assuming this would shpw that it is not stuck open as I normally have not gotten a reading of 90+psi.

I also put my car on ramps so I could get under it to inspect the entire path of the fuel line. Everything appears normal. There are no kinks or other types of damage to the line that may be causing an obstruction.

can you check the voltage to the fuel pump on the gray wire while idling to see if there is the low voltage or the regular current of 14v. if there is 14v while idling with car running we will check for a short to power in the circuit, if the voltage is 9 volts then we need to find a restriction in possibly the fuel rail.

Where do you mean to check the voltage? Should I check it directly by the fuel pump? It it accessible through the trunk?

right at the pump. its accessable under the car. the harness goes on top of tank and i think it enters from the rear of the tank. grab the gray wire

I got to the wiring harness right before the pump. I got 11v on the gray wire while the car was running and at slow idle. The engine was running at 800rpm. I was testing this by myself so it was a little hard but as soon as I turned the key to ON, I think I was getting 12.5v on the gray wire.

I got the quick disconnect on the fuel return line seperated. This is the one directly on top of the motor. I tried to blow some compressed air (40psi) into the line to see if there is a clog. It doesn't appear to be pushing the fuel in the return line back to the tank. Does anyone know if there is a trick to it? Does the key have to be turned to ON? If this does point towards a clog, where could it be and how can I get rid of it?

Hold everything. I was trying to blow air into the supply and not the return. I figured this out the hard way when I turned the key and fuel came shooting out what I thought was the return line.

Now that I have this figured out, I removed the real return line and ran a hose from the return line to a gas can, started the car and it was running at 48psi. When I disconnected the return line i could hear the faint sound of the fuel spilling back into the tank. I blew some compressed air (45psi) into the line and I could hear bubbles in the tank. I raised the pressure up a little(80psi) and it didn't seem like there was a larger amount of bubbles since there was alot more air. I reconnected everything and I was back to where I started. 90psi.

I'm going to double check the return line again tonight to see if I see any kink or damage but I'm pretty sure there wasn't any from when I checked it out the other day.

I checked under the car again to inspect the entire length of the return line starting from on top of the motor to where it goes on top of the gas tank. I did not see any damage or any sign of a possible kink in the line.
Any suggestion as to where I should go from here.

this is a real uncommon problem. i just had a camaro with the return line plugged with what appeared to be possbily sugar. next step is to remove fuel line at rear of fuel tank and run it into a tank of gas and see if the pressure is low, where it should be, if it is then remove fuel tank and fuel sender or check for a kinked fuel line at top of fuel tank. this is a fairly easy tank to remove.

Thanks for responding. I thought everyone gave up on me.
I have actually disconnected the return line by the rear tire and right above the fuel filter. I had the return line draining into a gas can and the pressure was still high. Now I also disconnected the line directly above the motor so with both ends disconnected, I basically have a line with both ends open. I tried to blow air into the line and it should be like trying to blow air through a straw but it's not. I have tried blowing air from both ends and almost no air at all will go through the line. So it seems the blockage is in this section of the line. I have checked the entire line again from the motor to the rear of the car and I again haven't found any kinks, crushed areas or any other type of damage to the line. I tried to push a small wire into the line from both ends but all of the bends are preventing it from going very far.
Any ideas would be greatly appreciated.

unfortunately the only thing to do is to cut it and narrow down where the blockage is. they have repair line kits for the plastic lines.

I'm sorry I never got back to posting my resolution on this problem. I think I started to write up the post but got involved with something else.

I ended up replacing the entire return fuel line. That did the trick in lowering the fuel pressure. I eventually got around to cutting the line up into pieces to see if I could find the blockage. Right at the spot where it changes over from the plastic/pvc line to the steel line, there was a white substance blocking the line. There was a pretty good amount of this substance that had a consistancy like toothpaste. I still have some on my tool box that never disappeared and it seems dry now and almost a little powdery if you rub it between your fingers. Any idea what the junk is?

I still have another problem which I was hoping would go away once this was fixed but it did not. I started another post titled "CAR BUCCKING ON ACCELERATION". Hopefully my car will be running right eventually.
Thanks for all your help.