John Gloyd

So, in the process of hunting down my running rich problem, some of you suggested checking my fuel pressure. Yesterday, I checked and at Idle I have 40psi but when I rev it, it drops to around 28psi and the the higher I rev the more it drops. When I shut the car off, the pressure drops to 0 instantly my Walpro 255 has only been in for ~1year but the Aeromotive FPR was in when I got the car. Which one do you think is the problem.

Please, all feedback is welcome.

F-Body drivers are: SMARTEST ON THE PLANET so Never drive faster than your guardian angel can fly.

____________________________________
Yellow Green 96' z28, M6, LT4 Hot Cam kit, 58mm BBK TB with bypass, Pro Mag 1.6RR, Comp’s Hardened pushrods, Comp’s HE Lifters, Extreme duty timing set, Aeromotive FPR, Pacesetter Headers, Flowmaster cat-back/no Cats & 3” pipe, K&N CAI, 160 Stat, Vortech Elbow, March pulleys, LT4 KM, B&M ripper, NGK TR55's, MSD Blaster coil, BMR STB, Walpro 255, 4.10’s, PCMFORLESS tune.

evilundisguised

What's the fuel pressure do when you disconnect the vacuum reference line to the FPR at idle? Replace your fuel filter lately?

ulakovic22

Check for fuel in the vaccum hose that goes to the regulator that will let you know if the diaphram is cracked or not. If the pressure is decreasing when you are asking for more why would you be running rich? Duck tape the guage to your windshield and find a road you can do a few WOT runs on and see what the engine does under load. I would think it would be your fuel pump since it can't hold pressure running or when you shut it off.

John Gloyd

I haven't tried removing the vacuum line but I replace my filter every three months. What will the vacuum removal tell me?


F-Body drivers are: SMARTEST ON THE PLANET so Never drive faster than your guardian angel can fly.

____________________________________
Yellow Green 96' z28, M6, LT4 Hot Cam kit, 58mm BBK TB with bypass, Pro Mag 1.6RR, Comp’s Hardened pushrods, Comp’s HE Lifters, Extreme duty timing set, Aeromotive FPR, Pacesetter Headers, Flowmaster cat-back/no Cats & 3” pipe, K&N CAI, 160 Stat, Vortech Elbow, March pulleys, LT4 KM, B&M ripper, NGK TR55's, MSD Blaster coil, BMR STB, Walpro 255, 4.10’s, PCMFORLESS tune.

Injuneer

Removing the vacuum line tells you what effect the intake manifold vacuum is having on your fuel pressure. Not likley it would be the cause of the pressure dropping to 28psi, unless by "revving" the engine you mean letting it sit at idle, and watching the gauge jump around, which proves virtually nothing. You need to check it on the road, under max RPM/max load. Snapping the throttle at idle is a huge waste of time.

The other advantage of pulling the vacuum line off is that you can see if fuel is in the vacuum line, indicating a leak in the fuel pressure regulator vacuum diaphragm.

You also need to consider that the Aeromotive AFPR's have been problem prone for years, to the extent that a couple years ago an Aeromotive rep came on this board and offered a free replacement of the AFPR's, no questions asked.

Why do you replace your fuel filter every three months?

Sweetred95ta

I was wondering the same thing. Unless he thought oil filter instead of fuel filter.

John Gloyd

The fuel filter is an inexpensive part so I change it after every three oil changes which I change once a month. I know it's not needed but I do it anyway. I will check the vacuum line for fuel but if there is none could the FPR still be the problem? Can a bad FPR cause the pressure to drop to 0 immediately after turning the car off? Or am I focusing on the wrong thing and should be looking at the pump.


F-Body drivers are: SMARTEST ON THE PLANET so Never drive faster than your guardian angel can fly.

____________________________________
Yellow Green 96' z28, M6, LT4 Hot Cam kit, 58mm BBK TB with bypass, Pro Mag 1.6RR, Comp’s Hardened pushrods, Comp’s HE Lifters, Extreme duty timing set, Aeromotive FPR, Pacesetter Headers, Flowmaster cat-back/no Cats & 3” pipe, K&N CAI, 160 Stat, Vortech Elbow, March pulleys, LT4 KM, B&M ripper, NGK TR55's, MSD Blaster coil, BMR STB, Walpro 255, 4.10’s, PCMFORLESS tune.

Injuneer

You can't be serious?

Loss of fuel pressure on shutdown:

-leaking fuel pressure regulator
-leaking injectors
-leaking check valve in the fuel pump.

You've got a couple items in there that are known problems..... the Aeromotive and the Walbro. They both seem to fail at a much higher rate than they should. Not unusual at all for the Walbro to lose the check valve, generally blamed on dirt getting into it during installation.

Also looks like you are copying and pasting your "quote" and your "signature" with each post. Why not use the "signature" field?