What should my fuel pressure be?

slc10844 · #1 11-06-2012, 02:58 PM

What should the fuel pressure be on a 87 Ranger 2.9? I checked my with a gauge and it has 40psi when you turn the key on and 28-30psi with the engine running. If I disconnect the fuel pressure regulator vacuum line while the engine is running it goes to 40psi.

Psychopete · #2 11-08-2012, 10:13 AM

28PSI is kind of on the low side, but everything else looks OK

FireRanger · #3 11-08-2012, 10:29 AM

All perfectly normal. That vacuum line's job is to reduce fuel pressure at idle.

slc10844 · #4 11-09-2012, 07:11 PM

Quote:

Originally Posted by FireRanger

All perfectly normal. That vacuum line's job is to reduce fuel pressure at idle.

Is 28-30 a little on the low side? I get an occasional hesitaion when I let the clutch out. I have 2 manuals. One says fuel pressure should be 35-45 psi and the other 40 koeo with 3-10 psi less koer. Thought 35 might be what it should be running.

FireRanger · #5 11-09-2012, 07:22 PM

nope, this all looks perfectly normal.

Psychopete · #6 11-10-2012, 03:24 PM

28 is low side of the spec, normally I have seen 30 and up running, but probably not low enough to screw up fuel atomization. at least change your fuel filter if you're not sure the last time it has been replaced and recheck. dirty filter will slow down fuel flow and hard on your pumps since fuel is what cools them and it makes them work harder.

FireRanger · #7 11-10-2012, 03:35 PM

At idle, the pressure is supposed to be lower. Vacuum is highest at idle, and causes the reduction.

Psychopete · #8 11-10-2012, 03:45 PM

it still needs to be high enough to get good fuel atomization despite the conditions, that's why the pressure is so high on EFI systems because of the injector spray pattern. I don't disagree that it's going to be lower at idle, but he is at the bottom of the spec

slc10844 · #9 11-10-2012, 04:03 PM

Been through the fuel system (fpr, filter 2X, injectors) and ignition (plugs, rotor, cap, wires). Even replaced tps. Hesitation less than it was, but is still there. Also has a rough idle. Other than that it runs great. Thought it might be a fuel pressure issue. If I pull the vacuum hose off the fpr with the engine running the fuel pressure goes to 40psi, rpm goes up and runs nice and smooth.

FireRanger · #10 11-10-2012, 04:52 PM

Quote:

Originally Posted by Psychopete

it still needs to be high enough to get good fuel atomization despite the conditions, that's why the pressure is so high on EFI systems because of the injector spray pattern. I don't disagree that it's going to be lower at idle, but he is at the bottom of the spec

That low end of spec is only at idle, when it is supposed to be like that. He even said that it reads 40 before starting the engine, as in no vacuum. Which is also perfectly normal. That indicates the regulator and the pump are working fine.