Fuel pressure test help!!!

**curt93t/t** · 03-16-2014, 07:44 AM

My car idles erratic and when I push the gas to the floor it sputters and RPM's don't really do anything. I'm thinking it is either my FPR or my pump is on its last leg. I got a pressure tester from AutoZone, but as you know our cars do not have a test port. I was able to connect an inline after the FPR where the return line comes off. Will I get an accurate reading by doing this? I am showing 9 psi on the gauge.

**mb3000** · 03-16-2014, 09:45 AM

Have you worked on the fuel system recently? I know that sounds similar to when the O ring on the pump/whatever else is being used is leaking. Could be a possibility that if a fuel hose was used to connect it could be one that was not approved for submersible use and is now leaking.

Could also be the pump dying. You said it makes 9 psi, you could disconnect the return from the FPR and run it to a bucket. Let the pump run for say 10 seconds. Measure the volume of fuel in the bucket and multiply by 6 to get the hourly flow rate. Compare with the pumps rated output at 9psi. Obviously doing this several times will help verify your results.

**OhioSpyderman** · 03-16-2014, 09:49 AM

Excuse me, but wouldn't he need to multiply by (6*60)?

Bob.

**Checkered vr4** · 03-16-2014, 09:56 AM

You have to read the pressure before the regulator to see line pressure. After is just a dump to tank. If your FPR is working correctly then it only dumps into the return after the pressure in the supply line is at 43 psi. (Or close to it)

**curt93t/t** · 03-16-2014, 10:17 AM

Haven't worked on the fuel system. A few days before I deployed on Feb 2nd my car lost power and would only idle erratically. I thought maybe the ECU was jacked because the car started working fine after I disco'd the battery and cleared two faults that popped up (barometric press sensor, ign coil) the same time the car started messing up. Went for a drive and after a few blocks the faults came back and car acted up again. Sent the ECU to AVPro and they said it was fine. I started looking at the MAP-ECU being the problem because I couldn't access the program, but it's working now and I still have the issue. Got a guy who upgraded his fuel pump, so I'm going to borrow his old pump and his FPR.

**curt93t/t** · 03-16-2014, 10:19 AM

Originally Posted by Checkered vr4

You have to read the pressure before the regulator to see line pressure. After is just a dump to tank. If your FPR is working correctly then it only dumps into the return after the pressure in the supply line is at 43 psi. (Or close to it)

So what you are saying is if I don't have any gas come out I'm more than likely not getting 43 psi through the rails?

**curt93t/t** · 03-16-2014, 10:51 AM

I cranked up the car with the vacuum line off the FPR and let it run for a minute. I pulled off the line on the FPR and didn't notice and fuel residue in the line. Cranked it up with the line off and the RPM's jumped to about 2 grand and I shut off the engine. A lot of gas came out of the FPR, so I hooked up the line again. Cranked up the car again and RPM's were still at 2 grand, but if I pushed the gas in the RPM's would fall and stumble.