I need help, my car is stranded at work. I'm pretty sure my fuel pressure regulator has died. When you turn the key to 'on' you can hear the fuel pump prime, but the FPR won't hold the pressure. It goes up to 40lbs but drops to 0 with in 5 seconds. If you crank the car the pressure will stay steady but when you stop cranking it, it drops to 0 again.

Its an Aeromotive A1000 and it's got to be less then a year old. Has anyone heard of these things dying all of the sudden? Could it be something else like the fuel pump letting the fuel flow back thought it?

 

The fuel pump doesn't run with just the ignition on. It will run for a second at first to prime the system prior to starting but won't keep it on.

The fact that it holds pressure while you're cranking says that it works like it's suposed to.

 

probably an injector(s) stuck open. It will drain pressure just like a pressure regulator letting pressure by.

if an injector is suck open...then...you're flooded too...which will cause the engine not to start.

just another possibility...

the fuel pressure regulator is a very simple mechanism and is very unlikely to fail...imho...i've never heard of one failing.

john

 

I pulled my FPR off and replaced it with one of my friends and it does the same thing.

I checked the impeadance on all the injectors and fired each one indivdualy, they all seem fine. Someone noted that I should test the check valve in the fuel pump. Does anyone know a good way to go about doing this?

 

I am not certain about this, but I have heard that some pumps don't hold pressure when they aren't running. Perhaps your pump is one that doesn't.

Are you having any other problems with the car that led you to investigate this? If not, I wouldn't worry about it.

-Max

 

Nothing is WRONG with your fpr , thats how they are designed to work , mine does the same thing and its a PAXTON of the same design. Those regulators are normally closed , when the pump starts the fuel pressure pushes it open , whatever pressure you get is based on the spring pressure you put on it with the adjustment screw. The vacuum pressure at idle has little or no effect on it especially on rotarys (lower vacuum , mine is -7"Hg), the reference line and diaphragm are for RAISING the fuel pressure when under boost.
You have another problem , if you have fuel pressure then what you need to look for is your spark (there could be two problems which cause the "lack of spark" , bad coil / wire or no ignition pick up signal to the Haltech) it can even be bad plugs , you just have to check over everything, most times its something very simple.

 

The vacuum does lower the fuel pressure, as it should. The regulator should maintain the same pressure difference between the manifold and the fuel rail. Lower pressure (vacuum) in the manifold should reduce the fuel rail pressure accordingly. Try disconnecting the manifold reference signal from the regulator at idle -- the fuel pressure should increase.

This doesn't really relate to the suspected problem at the start of the thread, though. His system won't hold pressure with everything off. That might be a leaky injector, or it might just be that his fuel pump doesn't hold pressure when it isn't running, which might be normal for that pump. The stock pump does hold the pressure when it is off -- I think most stock pumps do that for faster starts (since you have full pressure right from the start).

-Max

 

I did that already ( disconnect the reference line ) and at normal idle there is no change to my fuel pressure , only at deceleration where the vacuum can go as low as -19 or - 20 mm Hg would the pressure fall and it wouldonly fall by 2-3 psi.
Most after market pumps do not hold the pressure because they dont use a checkvalve in the discharge to hold the pressure when the pump stops, the regulator also would not allow the pressure to be held as it operates differently to the stock regulator . The stock one is normally closed at atmospheric pressure which is why it would hold the pressure when the car is off , vacuum in the manifold would pull it open to allow recirculation at light loads. As I said above the aftermarket reg.s are pushed open to the preset position by the fuel pressure .
I know it doesn't "really relate" , thats why I suggested some problems and possible solutions , but there isn't any reason why he and others can't benefit from some information at the same time.

 

That's not how my aftermarket, adjustable FPR works. I'm using the Aeromotive one. It maintains a constant pressure difference between the manifold and the fuel rail, which is what any regulator should do with the exception of ones without a manifold reference, or a "rising rate" (not 1:1) regulator.

Your pump might be overpowering your regulator or return lines, artificially raising pressure at times of low injector flow rates (which happens to be the same time you have manifold vacuum -- idle, light cruising).

Absolute vacuum is about ~33 inches of mercury. Since atmospheric pressure is 14.7 psi, you can estimate how many psi your fuel pressure should drop under vacuum -- vacuum / 33 * 14.7 = drop in psi. For 16 in Hg, your fuel pressure should drop about 7 psi, for example.

-Max

 

This happened to me because I had a haltech. You need the tach signal to fire the fuel pump during ignition.

Not sure if this is the case for you. Does your tack jump up and down when you crank the motor?

 

Yes, my tack does bounce. The car has been running fine, I've got almost 200 miles on it (fresh rebuild HBP )

Ever since I install my FPR it has ways held pressure, that is how I was able to set it to the proper fuel pressure with the car off.

I believe I have it narrowed down to one of two things.
A) either the bypass value in my fuel pump has gone bad and is allowing the gas to flow back into the tank
or
B) my connection where the haltech wires join up to the injector clips is lose and allowing one of the injectors to ground out and fire at random or fire continuesly.