Weird fuel pressure (zero) loss

[WhalePirot]

Zero fuel pressure - fixed

Finally; the engine all ready to fire. It rotated well and acted like it wished to run... no start.. CRAP! Someone is getting weary of this project, accentuated by the humid heat wave.

The first suspect, after checking the fuse, is the relay, having caused recurring problems. Consulting my self-colored, well-worn wiring diagram, I suspect the hot lead orange, or hopefully not, the ECM. A spare relay, that checked operable, proved no cure. I had been considering changing ALL those relays to solid state, like my fan now uses. There'd been no voltage at the fuse with the key on, but I later discovered there was indeed, w/in the initial 5 second turn-on, i.e. once I moved fast enough.

I applied 12vdc to the left pin of the fuse, and with a quiet garage, heard the pump run but there was zero fuel pressure! Okay, probably a filter; when did I last change it?

Meanwhile, I popped off the intake nozzle, ala 1987, to manually inject some gasoline past the TB butterflies. Crank; FIRE, for a second, as that meager squirt became exhaust noise. Okay half the requirements for a running IC engine are okay: ignition. I'd nailed TDC with the help of a boroscope. It is so cool to watch the valves open and close!

Back to no fuel. Using a troubleshooting technique from my Bell & Howell TV course; half-split the circuit. I removed the steel fuel filter and could easily blow through it.. yummy! Then, using compressed air, the line to the tank seemed good but to the fuel rail, no indication of any pressure. Strange. Only hard line forward, so what could obstruct? Did a steel line get twisted? Nah.

I removed the shraeder valve and applied compressed air both directions, through it and to it. Some fuel exited rearward but nothing moved forward. The local brain trust thinks the flexible portion of the fuel line has deteriorated internally and is acting like a flapper valve; a one-way valve.

I really hope someone else has seen this and knows a fix; hopefully not removing all the A/C, hoses, etc. that are in the way.
That, though, is still preferable to (also) removing the SuperRam ..... again!



Yes, Alice, there is plenty of gasoline in the tank.

 

[WhalePirot]

line from filter to rail connection okay.

 

[WhalePirot]

Zero fuel pressure with pump running via jumper wire; everything plumbed up. Seem some small fuel puddling atop the intake.

dammit

 

[WhalePirot]

Removed the SuperRam to inspect the fuel rail, etc. Everything looks normal with no leaks when pressurized, however zero psi indicated.

Despite the AFPR (aftermarket) [AFPR= Adjustable Fuel Press. Regulator] appearingfine, holding vacuum from my hand pump and is only 6 or so years old, I removed it. The diaphragm looks new new and installed properly, as do other parts, minimal as they are. Reinstalled; no change.

Removed the AFPR again, and ran the FP.. nice squirt of gasoline! I checked the pressure and it pegged my old gauge which only goes to 15 psi or so; way below what is correct. The only FP gauge I have has a Schroeder connector so I am weighing getting another gauge before throwing another $90 or so via a new AFPR. The stock one is hiding in my garage, of course.

Things do that, until I don't need them. ad

 

[John Robinson]

I had a similar experience with a motor cycle. It turned out to be a small electrical wire twist connector had somehow gotten sucked up into the pick up tube in the gas tank and it was lodged there acting as a plug in the fuel line. It took me 3 days to find this one. The bike was a BMW with a igntion fuel system almost like the Corvette.

 

[WhalePirot]

thx

Grateful for a reply, John. That's a weird one, too. I may pull the fuel pump to inspect the sock-like filter, but would prefer to verify adequate pump pressure. I don't want to throw parts at this.

I won't start on "German engineering", either.

ADDED: I made up an adapter to check the FP at the AFPR internal hole, using my gauge. FP was 60+/-, so I am changing the diaphragm.

No luck. Then I learned from a kind expert that it IS possible to connect the feed and return lines backwards. He was man enough to explain that he'd done it. The fuel enters through the larger steel line into the rails, then goes to the FPR, which returns excess fuel through that '3rd' hole in the FPR to the smaller steel line, to the tank.

The squirting from that 3rd hole meant the return line was pressurized... only. "I hadda feeling.. a feeling deep inside, oh yeah".

 

[John Robinson]

Backwards lines sounds like a real possibility. Are you saying you checked it out and they were backwards? Last month I had the right side door panel off and I had removed the wires from the power window switch. The next day I put them back on the switch and found that my memory was not so good as the up button had the window going down and the down went up. It only took me 7 days to find which wire went were. My FSM simply did not make any sense because the switch they showed was not the same as what is in my car.

 

[WhalePirot]

I am about to try to reverse those lines. The steel has a definite memory and shape, which seemingly would disallow revefrsal.



Added: I reversed the fuel lines at the rail and got 44 psi, with the old regulator. The car runs, after 4 hours or SuperRam reassembly, but needs tuning... in progress.

 

[Schrade]

Start with static fuel pressure, including bleed-down time - plotted on paper time vs pressure.

Bleed-down through injectors, FPR bladder, leaks in line, etc.