...on a 1988 S4 stock engine could my malfunctioning Fuel Pressure Regulator cause low enough pressure on the fuel rail that would not allow fuel past the injectors?
thanks for any advice.

 

BUMPITY

 

You still having problems, Harley? j/k...First of all, if the car won't start, this won't work (or maybe it will?), but pull the vac line of the FPR, this will (in theory) raise the fuel pressures in the fuel lines (same thing happens during a hot-start condition if the system is functioning O.K.)...This MIGHT let you know if the FPR is going bad or not, I dunno...If the injectors are opening at all, the fuel pressure would have to be awfully low to prevent lightoff, IMO...

 

Yes. Im still having problems...installed a fuel pump cutoff switch to stop what I thought was leaky injectors and that did not help so I now know that the problem is that at times there is no fuel getting past the injectors and I know the pump is good , lines are clear, new filter, and then all of a sudden she will fire up and outrun my other REX without missing a lick,,,I've got to find out why no fuel is getting by the injectors, now I think its because for some reason the fuel pressure drops and I've tried crimping the vacuum to the FPR and that doesnt help either. Im thinking the diaphram in the FPR is loose and sometimes stops the flow, but would not that cause an increase in pressure.
One thing for sure, when it doesnt start, she is NOT flooding and the PLUGS are dry as heck...

 

I've never torn ours apart, most most pressure regulators I've worked with over the years are nothing more than a ball, a spring, diaphram, and sometimes a pneumatic or liquid source for reference pressures (like the vac line on ours)...that being said, they're such simple animals they rarely go bad (unless it's been sitting, varnishing up over time)...Are you seeing/ smelling any fuel whatsoever in the upper chamber when you disconnect the vac line? If not, I wouldn't suspect a bad diaphram...Also hate to sound like a broken record, but have you certified a good ground on that rear rotor housing? If questionable, make a new ground with a ring terminal on both ends, and attach one terminal directly on top of that existing rotor housing ground, and the other to the firewall, using one of the many bolt hole locations in the area aft of the engine...see if this helps, if you've run out of options...

 

Wayne, are you talking about the ground from that bolt that runs to the bare connector coming out of the firewall ? I can redo that one,,,it looks ok but maybe its been compromised...

 

Bump

 

No Harley, the ground that is already there goes to the tranny bellhousing area...the problem I see is that it happens to be the closest ground to the one on the rotor housing upper surface we've been talking about- which means current has to run through the rear housing/ rotor housing interface to reach that harness ground (and if your engine's like mine, there's no metal-to-metal contact there- it's all hylomar )...I am talking about adding an entirely new ground cable- from the one on the rotor housing (leave the original in place) to a spot of your choosing on the firewall...

 

OK..there is a bolt just past the oil filter so I took it out, cleaned around it and ran a ground...it appears to be on top of the rear rotor housing just in front of the tranny...I'll try it over the next few days...thanks as usual Wayne...and everyone else that always tries...