Fuel Pressure Regulator Problem

Fuel pressure is set at 4o psi on an adjustable FPR, with the vacuum line disconnected & plugged. When the vacuum line is connected, fuel pressure should drop to 30-35 psi at idle with 20-22 inHg vacuum. Mine doesn't drop at all. Diaphram is not torn or leaking. It holds vacuum properly with my hand vacuum pump. It was not a problem with the old fuel pump which would only supply pressure at idle. The new pump is a 255 lph high pressure Walbro in-tank pump (GSS-342). Can a 2 year old Kirban just wear out?
Everything is reporting a fuel rich condition: EEC bad codes (HEGO's out of range), poor engine idling, exhaust popping, my nose, my ears.
I had a Mallory AFPR working with no problem for 15+ years. It needs a new o-ring. The Ford one might go back in, it needs a new o-ring, too.

It takes me a lot longer to change, must be doing something wrong. Yes, connected & disconnected with engine running, no change at all, i.e. both dynamic & static tests, same results. Diaphragm is replaceable, pulled the cover, all looks normal, but diaphragm doesn't seem very stiff. The Mallory is a lot more rigid. Tried to set pressure lower, but 1 turn was like 1 psi; didn't seem to do much when engine was running. With fuel pump only running it was more responsive. This was the 2nd time the car was running with the new fuel pump. BTW, there is no piston inside. I'm calling Kirban today.
http://www.kirbanperformance.com/product/776/Mustang BILLET ALUMINUM ADJUSTABLE FUEL PRESSURE REGULATOR #5005.html

UPDATE: Kirban says the only thing that would cause these symptoms is a restriction in the return line. The new high pressure/high flow pump will overpower the FPR if there is any kind of restriction. The FMU is coming out. Might not need it, Kirban AFPR does boost compensation. The inside is quite a bit different from my Mallory AFPR.

Took the FMU out of the return line & the FPR functions normally under static testing. Not sure why. FMU should have no effect at vacuum conditions. It only begins to close at positive pressure (boost). It has something to do with the high pressure, high flow fuel pump, since that was the only thing that was changed. Will be dynamic testing (engine running) soon.

Car was running 7 days ago, enough to get to the gas station. It was running rich, but making good power & idling fine. Pulling vacuum line from FPR had no effect on gauge reading 40psi, even though FPR has dedicated vacuum line & vacuum is 18-20 inHg. Removed FMU & now vacuum line connected to FPR has desired effect of reducing fuel pressure. Not sure what FMU has to do with it because it doesn't begin to close until pressure builds in vacuum line. It's all new except for the housing. Bench testing verifies it's all good.

Take it out again 2 days ago, & engine is breaking up under load like nothing was ever done.

Yesterday. disassemble FPR, all looks good. Disconnect return line fitting at tank & blow out entire line with compressed air from the FPR. Then blow from disconnected hose to tank where it seemed it dislodged a blockage in the hose. If there was something in there, it's now in the tank. Reassembled FPR, connected remote Fuel Pressure Gauge to the Schrader valve & road tested. Power is good, fuel pressure is good, but now it won't idle. It just dies after start.

Found Schrader adapter for remote pressure gauge to be defective, too tight or too lose would not allow fuel to pass through it; disassembled adapter, modified it & now works as it should.
http://www.actron.com/product_detail.php?pid=16173

Bad Codes, all codes were cleared before testing today.
29-C -Insufficient input from vehicle speed sensor. Not connected to EEC, don't care.
66-C - MAF sensor went below 0.4 volts during the last 80 warm-up cycles.
67-O - Neutral safety circuit failure.
95-C - Fuel pump secondary circuit failure. The EEC senses infinite resistance to ground from the fuel pump on the Fuel Pump Monitor circuit.

67 & 95 make no sense at all. 66 may account for the no idle condition.

Every time I fix something, another gremlin appears.

txstang84 said:

1. Damn...so you can hold the idle up, and it's ok, but if you let it idle down, it dies...
2. You reconnected all the vac lines and such right?

Click to expand...

1. Correct. If you let it coast to a stop it will die, too. Will have to rebaseline TB & IAB, but all was good a week ago except for the rich condition.
2. All reconnected when the upper went back many weeks ago. I suppose a vacuum line could have broken in the interim. Will have to check again. I do notice that vacuum went from 20 to 18 inHg at idle, but it doesn't really idle unless the throttle is feathered. Could be an electrical connections problem because I'm getting codes never seen before. First time I ever saw 29-C, Vss has never been connected, never seen any of those other codes, either. I checked the 10-pinners a few months ago, may have to go back & do it again.

Zombies
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Zombie Hunter weapons aren't working. Call in Seal Team 6.