Fuel pressure issue

[Green72]

I have a 67 GTX with a 440. About two years ago I installed an Atomic EFI throttle body. Intank pump is a PA series from Tanks Inc. and the pressure regulator is from Aeromotive. I recently noticed that the fuel pressure was a little lower than it had been. It is running at about 38lbs. and was set at about 50lbs.. So I attempted to adjust the pressure with the regulator but can't change the pressure up or down what so ever. My question is would you suspect the regulator or the fuel pump? Any tips on trouble shooting would be great.

Thanks

 

[493 Mike]

I have a 67 GTX with a 440. About two years ago I installed an Atomic EFI throttle body. Intank pump is a PA series from Tanks Inc. and the pressure regulator is from Aeromotive. I recently noticed that the fuel pressure was a little lower than it had been. It is running at about 38lbs. and was set at about 50lbs.. So I attempted to adjust the pressure with the regulator but can't change the pressure up or down what so ever. My question is would you suspect the regulator or the fuel pump? Any tips on trouble shooting would be great.

Thanks

Does the gauge drop when the system is bled down? Sounds like a regulator problem otherwise.
Mike

 

[wagonman]

If you have a return line plug it at regulator then pump should go max pressure. Or hook up a gauge at the pump supply line. Got a fuel filter on it? You can rent the gauge at most parts houses, just hope some animal did not drop it.

 

[Green72]

Does the gauge drop when the system is bled down? Sounds like a regulator problem otherwise.
Mike

Yes the gauge goes to zero when bled down.
For testing purposes I eliminated the filter, it is not the problem.
I suspect the regulator, so your tip about plugging return line should tell me what I need to know.
The regulator is not very old and has very few hours on it. I believe after looking at things that it is just letting fuel flow freely through with no restriction
Thanks for the input
Green72

 

[HT413]

Only things I can think of besides what was mention is to check the pump is getting full voltage. Also, if the EFI is controlling the pump, check that it is calling for enough fuel. Some EFI’s can knock the pump down to below 50% capacity by pulsing the voltage to the pump (called PWM - pulse width modulation)

 

[steve340]

I would check the gauge first. When you know it is right you can make moves.

 

[tonysrt]

I don't have a regulator on my F.I. because the pump supplies 58 psi. Your regulator is probably restricting the pressure. Does Atomic require 50 psi?
I have FiTech and they want 58 psi.

 

[wagonman]

Yes the gauge goes to zero when bled down.
For testing purposes I eliminated the filter, it is not the problem.
I suspect the regulator, so your tip about plugging return line should tell me what I need to know.
The regulator is not very old and has very few hours on it. I believe after looking at things that it is just letting fuel flow freely through with no restriction
Thanks for the input
Green72

All good ideas, but lets start at the pump. Remove the pump wire connector to take the ECU out of the picture. Then hook up a gauge to the pump or filter. Apply 12 volts ( fused 10 amps please ) and ground. This will be dead head pressure = max. Observe pressure. If it goes to max and holds pump is good. It should hold max for about a minute,the check valve inside the pump wont hold it forever. If good then move forward in the system. I would be nice if you have a Lab scope to check pump wave form. Is this a returnless system IE one line?

 

[Green72]

So problem solved. It was user error I have to admit! When HT413 mentioned the EFI controlling the fuel pump it made me go investigate. Somehow I had set the controller for the EFI to the wrong type of pump. Had it set for a PWM pump but I have a non PWM pump. I have tendence to over think things.
Thanks for all the help

 

[Green72]

Also if anyone is wondering the Atomic EFI is awesome