Fuel pressure problem!!

**Ain't Right** · 08-19-2011, 11:40 AM

Hello! I've found tons of life-saving info on this site over past couple years, and now I have a question I hope some of you may can answer for me. I have a 2001 Trans Am, automatic. I recently replaced the fuel pump motor, and made the trap door to make re-entry easy for future problems such as this. I drove the car with a fuel pressure gauge, at Idle it maintains 55-60 psi but as soon as you take off it goes as low as 20psi and lower. No SES or check engine lights come on. They have come on before if the gas cap wasn't on tight, so I drove it a few times, restarting the engine each time, with the cap off, and the car ran just as crappy and still no lights were triggered. Would this indicate a bad fuel tank pressure sensor, fuel pressure regulator(intank), or fuel pressure regulator sensor, or are these each one and the same? If it is the tank pressure sensor (which looks similar to a MAP sensor) is it possible to change without actually removing the pump assembly from the tank since it is visible on top of the assembly? If more info is neede, please ask, and thanks in advance for any input!

**cammed goat** · 08-19-2011, 03:16 PM

What pump are you using?

**Too Fast** · 08-19-2011, 03:32 PM

Fuel tank pressure sensor is for emissions only, it does not check fuel pressure at the rail. So, that won't have any effect on fuel pressure. When was the last time you changed your fuel filter. How is the integrity of all the fuel lines from the tank up to the injectors? Any kinks? Especially near the filter.

**Cutlass** · 08-19-2011, 03:50 PM

fuel filter or pump, I'd guess

**cammed goat** · 08-19-2011, 03:56 PM

I was also thinking that if OP is possibly using a Racetronix, there is an amplifier harness that, if not used, will cause running/drivability issues.

**Ain't Right** · 08-21-2011, 05:47 AM

I have a 255 pump from TRE Performance. Install went smooth no problems. New fuel filter. Recently had fuel sytem flushed at the dealership. No leaks anywhere. I've found a regulator for inside the pump at ABC auto and the tank pressure sensor. May have to throw the regulator at it and see how it turns out. Concerned however that the ses light no longer comes on with the gas cap off as it has before. I didn't know it the pressure sensor in some way told the computer to control the pressure regulator what to do or what. Probably should have just bought the whole assembly to begin with. Anyway, it drives around ok for the most part, but it's when you get on the gas the presuure drops drastically. The pump has been in for two months before this started. Just got the car back from a transmission rebuild on the last week of the 1 year warranty and now this. Transmission has been rebuilt about once a year since I bought it, and noone seems to be able to do it right or figure out what causes it. I pamper this thing and it doesn't see any abuse other than the occasional back country highway highspeed cruising. There is no redlight to redlight drag racing or anything like that.I knew when I bought it 7 years ago I'd be throwing parts at it but now I'm just ready to turn it into a rolling ball of flames. I love this car, but I think I see the real reason they stopped production back in 2002.

**Kordril** · 08-22-2011, 09:50 AM

I have a 2001 WS6 6M that now has an LS6 in it...and I have the exact same symptoms and was assuming either a dying fuel pump or FPR...I'm curious to hear others opinions on these symptoms.

**Ain't Right** · 08-22-2011, 11:24 AM

Thanks for the input. I think I'm going to go aheaf and try replacing the in-tank pressure regulator. Does anyone know thw part number and or where I can aquire one? Seems all I can find is the fuelrail one for older models.

**cammed goat** · 08-22-2011, 01:53 PM

Keep us posted. If it isn't the regulator, then maybe the pump isn't putting out enough fuel for the engine's demands.

**Cutlass** · 08-22-2011, 05:42 PM

Originally Posted by Ain't Right

Thanks for the input. I think I'm going to go aheaf and try replacing the in-tank pressure regulator. Does anyone know thw part number and or where I can aquire one? Seems all I can find is the fuelrail one for older models.

Good luck. I don't think they are sold separate. You could try calling a few parts stores and see if they can come up with something. Or buy a used 99-01 fuel pump bucket and hope the regulator is ok.

**Ain't Right** · 08-23-2011, 04:59 AM

Found regulator seperate at racetronix and NAPA. Nobodyelse can get it.

**Cutlass** · 08-23-2011, 05:56 PM

nice!! good to know

**nomasterase** · 08-24-2011, 01:30 AM

Might wanna check and make sure the hose that connects the pump to the bulk head isnt split in the tank or otherwise leaking too

**Too Fast** · 08-24-2011, 02:13 AM

If the regulator doesn't help, I'd be double checking the fuel line again, and if that all checks out, I'd get a different new fuel pump.

And if you are just going to burn the car down, please let me have it before you do!

**Ain't Right** · 08-24-2011, 10:46 AM

Will definately be checking everything when I pull the pump. At least I don't have to drop the tank!

**Ain't Right** · 08-27-2011, 09:19 AM

Just finished installing the regulator from NAPA and all is good!

**cammed goat** · 08-28-2011, 01:57 PM

Good to hear!

**Ain't Right** · 08-29-2011, 07:59 AM

Well, ran like a new bird then started bogging down and feeling like the breaks were on. Las time this happened was 30,000 miles ago when the cats failed, literaaly at 79,890 miles, just in time for federal warranty replacement

) this morning however, it ran like a champ on the way to work. I had reset the computer for idle as soon as I finished the install, hopefully it just needed to purge the line since before I pulled the pump, I let the motor idle with the pump wire harness detached to clear fuel from the line and release the pressure. Hopefully it will run as well this afernoon when its 108 degrees outside as oppossed to the 79 this morning.