All_Z_Way

I think I know the answer to this already, but for a little confirmation can someone let me know about how to verify a fuel pressure regulator failure.

On my '93 Camaro-Mustang Challenge race car, I yearly have to have a dyno certification.

I had my dyno a week ago and the numbers looked bad and the car is running extremely rich.

In the yearly process, we have to record our fuel pressure. Now the fuel pressure itself looks normal and appears normal. It is around 40psi with the vacuum hose connected and roughly 42-42 with the vacuum hose disconnected.

However, I noticed that when I pulled the vacuum hose, a considerable amount of fuel was coming out of the vacuum hose.

This is a sign that the regulator is bad.. correct?


On a '93, do you have to remove the fuel rails to replace it?

If the regulator is not working correctly, could this be the reason the car is running so rich and also a possible cause of the poor dyno run?


Thanks,

James

RamAir95TA

Fuel in the vacuum line is a dead giveaway that the regulator is bad. What happens is the fuel that leaks through the vacuum line and into the manifold is also being burned, which is why you're running rich. There is a rubber diaphragm in the regulator that if torn will cause it to leak.

You PROBABLY could replace it on the car, but the fuel rails come off with four bolts - just take the rails out.

All_Z_Way

Thanks Joe... When I found fuel in the vacuum hose and haven't seen it in the past... I figured it was bad.

I am now hoping that also caused my poor dyno. If not, I may still have other issues causing the engine to be down on power so bad.

Injuneer

When the FPR leaks fuel into the vacuum line, that fuel ends up pouring into the intake manifold, between cylinders #6 and #8. It is important that you immediately check your oil for fuel dilution. The excess fuel washes down the cylinder walls, gets into the oil, diluting it, and can do serious damage to the engine. Would definitely explain poor dyno results. But it should have shown up on the dyno wideband graph.

All_Z_Way

Thanks Fred... I will be changing the regulator before I start the car again and I just changed the oil, so I should be good there.

James

97WS6SCharged

If you made any changes to the fuel or spark curves you may want to undo them once you change the regulator.

JFR

I'm going to change my fuel regulator, I have close to 90 lbs when I turn the key, and pump comes on. (will not start,too rich) No fuel out of vacumn line of regulator.
I have hear all the problems with low pressure from the regulator, anyone with high pressure?
Frank

Injuneer

I believe you just changed the fuel pump. Did you have the high pressure problem BEFORE you changed the pump? Or only AFTER?

Is is possible you hooked the pump up wrong and something is blocking the return line? When the pressure rises, the fuel pressure regulator opens up, to allow the fuel to return to the tank. If the return line is blocked, or for some reason the FPR isn't opening, you will see the shutoff pressure of the pump.

Or, remote possibility, do you currently have an Aeromotive aftermarket adjustable fuel pressure regulator?

JFR

Thanks,
Just for info. I worked for 3 days trying to get the 3/8 inch line off fuel rail using plastic tools.
When and bought a metal one from Napa and took 30 seconds and it poped off, also the 5/16 inch one also, one tool does both.
Hope this saves someone else time and brusied hands.
Fuel return line plugged, no return, high fuel pressure....bugs in the line from sitting 7 years.......
10/08/13
Had high fuel pressure again 60 lbs. Checked return line, it was clear.
No fuel leaking from regulator vacumn hose. After removing old regulator,found dirt in screen, dirt flakes both in and out lines of reg.
95lt1 stock
You guys are the greatest.
Frank