Fuel Pressure Question ?

Mr. Quik · Nov 16, 2009

Hey Guys, I'm in need of a lil help.......
I installed a FPR on my 94 and what's weird is that when I prime the system before starting the car my pressure gauge doesn't display any pressure, but when the car is started and running, vacuum off the gauge reads 39psi. My question is, shouldn't when I prime the system see a pressure reading on the gauge, as in the system is holding pressure ?

Paul · Nov 16, 2009

Yes, if you cycle the key on a few times, you should get pressure in the system.

toyman · Nov 16, 2009

Paul said:
Yes, if you cycle the key on a few times, you should get pressure in the system.

Why does he have to do that? The FP starts as soon as the ignition is in the run position. My gauge shows pressure immediately.

Paul · Nov 16, 2009

The pump only turns on momentarily when you first goes key on. The hall effect sensor in the distributor is what keeps it running. So your pump may not pressurize the whole system with the first key on. It might take two.

MustangChris · Nov 16, 2009

Paul said:
The pump only turns on momentarily when you first goes key on. The hall effect sensor in the distributor is what keeps it running. So your pump may not pressurize the whole system with the first key on. It might take two.

is this why you are supposed to turn the key off and on 3 times before starting the car after it runs out of gas? or is that an old wive's tale?

toyman · Nov 17, 2009

Paul said:
The pump only turns on momentarily when you first goes key on. The hall effect sensor in the distributor is what keeps it running. So your pump may not pressurize the whole system with the first key on. It might take two.

Okay, I guess. As I have a high pressure/high volume pump I've only seen full pressure on the gauge when the ignition is turned on. Good to know that there are always exceptions.