Fuel pressure low?

[Cwhatfield40]

I put my fancy fuel pressure gauge on today and I am getting 30psi at idle. 42 psi at idle with the regulator unplugged. 40 psi WOT with the gauge taped to the windshield. That sounds real low to me, is this normal for a 1984 SVO?

[BrianO]

not normal for any of them.. 1 psi for every psi of boost it should rise.. maybe your FPR is toast or the pumps are shot.

[Cwhatfield40]

Well, i am worried about running lean and so I pulled my plugs... they look normal, but I plugged my knock sensor back in until I can diagnose the FPR or pumps (Prolly replace the pumps with a filter and 255lph). Car still pulls strong to 6200rpm. I am going to check the calibration on my gauge too. Thanks Brian!

[BrianO]

don't forget to upgrade the ground wire for the tank pump when doing that swap, our cars need it to be enlarged. it's here somewhere...

[svono50]

Like Brian mentioned, you should get ~1psi increase with each 1psi of boost, so considering you are seeing 42psi with the regulator unplugged (i.e.- = 0psi boost), you should see ~57psi of fuel pressure @ 15psi of boost. If your gage is showing only 40psi off fuel at full tilt you have something restricting flow. I would surely recommend to keep your KS plugged in with your current information.

Your FPR could be the culprit and easy to change, but make sure your filter is clean/new to start with too. A lot of 84/85 owners here prefer to keep the dual pump setup, so you may want to do some searching to determine what route you would rather go, single or dual. Your low pressure in-tank pump may be having issues restricting what the high pressure external pump can pull. 84's are also known for their wiring insulation issues, so make sure you have good power back at the pumps. Good luck.

[Cwhatfield40]

You would think that with only 33000 miles this thing would be mint, but 27 years is still a long time for everything to rot! I just keep finding more little things... diaphragm here - diode there.

[SVOeric]

most of the guys with low-mile cars found that time seems to be harder on them than usage.

[Cwhatfield40]

OK, so the other day I noticed that the in-tank pump was real noisy... squallering and surging even though the idle was smooth. Then today it just quit making noise. So it comes and goes, I guess that new fuel pump is closer than I thought!

[Cwhatfield40]

Update: the in tank pump got very loud the other day... I mean I could hear it over the wind noise with the windows down. I could almost go 55mph just barley pushing the gas in each gear to get there. Limped all the way home with people driving crazy all over my seemingly conservative rear. I assume the inline pump is the only reason the car was still running. You could turn the ignition off and back on and the pump would run for a bit then crash again over the slight bump in the road. I ordered a Walbro GSS340.

[Desi]

Ok, not to hijack, but where do you test the pressure at? I can't find a schrader valve anywhere on/near the fuel rail.

[Cwhatfield40]

I use the schrader valve on the firewall. It points towards the front of the engine. The fuel pressure should be similar anywhere on the primary side of the fuel system.

[Cwhatfield40]

A closer pic of the schrader valve.

[Desi]

Ok, yes, I have that.. didnt realize what that was, I thought it was part of the AC system... you don't have an adj. fuel regulator by chance do oyu? if so mind posting a pic of how it looks?

[Cwhatfield40]

I do not have an adjustable fuel regulator on this particular car. The fuel regulator is located to the front of the intake just behind the alternator. It has a vacuum line going straight into the side of the intake. Usually all you have to do is loosen the nut around the adjustment screw and turn the screw back and forth and observe the reading on the fuel pressure gauge attached to the schrader valve. READ the post above from svono50 for the settings.

[SVOeric]

Well even if you did have a pic of YOUR adjustable regulator, that don't mean it's going to be the same as his adjustable...
Each one is different, it depends on the brand and design as to where the adjustments are