Blocked fuel return line?

[Zero Signal]

So the car is up and running again after replacing the head gaskets and valve stem seals and a new water pump. Immediately, the idle loped more than it should and the engine has an erratic shake to it. Then I took it for a spin and noticed that anything more than very slight thottle causes the car to chug and surge. It drives just fine if I stick to just touching the throttle to get around. When I do give it more gas, it's super jerky when I let off it. At first I thought the timing was off since it's so touchy at tip-in throttle, so I adjusted it to 10 degrees to no avail.

The last time I had a similar issue, it was a bad fuel pump. My pump has been whining unusually loud this weekend, but it's brand new. I checked my fuel pressure at idle. It's about 82psi with and without vacuum on the FPR Pulling the vacuum line off the FPR has no affect at all. When I pinch the return line, I can see maybe a 1/2 psi bump in pressure. With the engine off, it holds almost 40psi for quite awhile. Could the FPR fail in this manner, by basically causing too much pressure all the time? I can hear the injectors ticking away when I have the hood open. That's pretty odd since I usually need the stethoscope to hear them. My other thought was that maybe the return line is clogged somehow?

 

[revhead347]

It might be a clog, but more likely a bad FPR.

Kurt

 

[Zero Signal]

I'll just pick up a new one and see what happens. It's an easy enough change. By the time I have all the kinks worked out of this thing, almost every part of this motor & fuel system will be brand new

 

[Zero Signal]

No luck tonight with a new FPR. Still at 85psi all the time and the pump is whining under pressure. Tomorrow night, I'm gonna pull the return line off and try to clear it with the air compressor nozzle rammed into it.

Will I wreck the pump/injectors if I continue to drive it?

I'm getting the CEL on and off. I'm thinking the EEC is reaching its limit on leaning it out.

 

[revhead347]

I think you could cause some problems if you keep driving it.

Kurt

 

[HISSIN50]

Are you totally sure the gauge is correct? Will it prime all the way up to 80+ PSI or does that only occur while idling?

Any idea on what codes it's spitting?

I was trying to think of how one could safely rig up a temporary return line (to maybe just prime the system a time or two and see if pressure stabilizes at 40 PSIG).....

 

[Zero Signal]

It primes to 38psi and holds it, but while idling, its steady at about 84-85 psi. As far as I can tell the gauge seems ok. I think the loudly ticking injectors and whining pump defend the high reading too. I may take it down to Oreilly and run codes. I suppose I could hook up the inverter, get the dead laptop out there and see what the tweecer has to say . . . I may find the PWM why out of wack.

I could probably find a vacuum or fuel line that fits tightly into the return line coupling on the rail and prime it a few times into a gas can or bucket to see what happens. I'm wondering if I could use the air compressor to back wash the line.

 

[revhead347]

I don't think it would hurt anything to wash out the line with compressed air.

Kurt

 

[HISSIN50]

I could probably find a vacuum or fuel line that fits tightly into the return line coupling on the rail and prime it a few times into a gas can or bucket to see what happens.

Since the prime-out pressure is within spec, one would want to do this with it idling to see if the return line was the issue. However, the fire/explosion danger goes up quite a bit with it running vs simply priming.

One can simply use a paperclip to run codes.

 

[Zero Signal]

I'm an idiot

 

[revhead347]

WTF is that?

Kurt

 

[HISSIN50]

Paper towel to keep debris out?

 

[Zero Signal]

I shoved those blue paper shop towels into the couplings to keep stuff out while the manifold sat on my garage floor. I made the mistake of not looking into the coupling to see if any towel got broken off before plugging in the return line

I wonder if I can return my new FPR

 

[kjohnson1]

That I found funny. I'm glad no one said anything derogatory. That's something i would do. I found this post trying to find ideas why I'm 15% too rich across the board with a 95 3.8L Mustang. I'm hypothesizing a blocked fuel return line.