75 1.8 L-jetronic, Fuel Pres?, Regulator? Pump? Returns??? Options

[Donaldo88]

Hi again. Second post...again on the 75 1.8, a sort of time capsule car, with only 39K miles, which seems to be plausible, and it still has L-jetronic FI. Virtually no miles driven in the year we've had it, because there's one problem after another. The latest, it quit running, with clearly a fuel problem, but I'm not ready yet to tow it. Using Haynes manual, it recommended checking fuel pressure. I special ordered a guage from Auto Atlanta, but I gave up on it ever coming, and canceled it. Rigged up my own guage, but had no tee, so end-connected it into the fuel line on the left bank, looking for 35#. Got 90# on the guage, and squirted a little gas out the return line on the right bank, so shut off switch momentarily. Called Auto Atlanta to see if they recommended a new regulator, as my Haynes book recommended. The guy I talked to asked George, who said "the regulators never screw up, sounds like the return line is plugged up". Seems like if I had crud in the line, it would plug injectors way before plugging the return line. Do you know...if my left bank distribution was open, does that screw up a feedback signal from the injector, causing the over-pressure? Apparently there's check valves in the returns, because the open left fuel line didn't flood the engine compartment with gas, which would be the case if both banks connect together. I see some braid lines when I look up from underneath, but I don't see the two poly lines which exit the engine and go into the tunnel. It looks like I have to take out the fuel tank to see more or clear the lines.....any suggestions, or experience with this?
Thanks,
Don

[SLITS]

In one of the rails (passenger or driver) there should be a tap in the middle .... it is a 7mm bolt (also the fuel line to the cold start injector could be attached there). That is where you tap for fuel pressure. You "deadheaded" the pump and that's why you saw 90 psig.

And 35# is to high and might cause injectors to leak. 30# is the setting.

If you can't find a tap then connect your guage to one of the injector taps on the rail.

Fuel flow: Tank to filter to suction side of pump to discharge of pump to pass side fuel rail across engine to driver side fuel rail to pressure regulator to return line to tank. Fuel pressure to system is measured in the bold area.

The return line is a free discharge to the tank. Take the line off the fuel pressure regulator (hose runs on back of engine to passenger side) and blow into it. If you hear bubbling in the tank or can even blow thru it, it's not plugged.

[Dave_Darling]

L-jet pressure is higher than D-jet; I think it's about 34 PSI with no vacuum on the line to the regulator? Haynes has the numbers.

Oh, and your post is a much better explanation than my own attempt over on the Bird board.

--DD

[Donaldo88]

Thanks everybody. I found that itty-bitty tee, but having no connector to screw into it, I tried the barbed connection into the rubber fuel line. Gotta cut it and find a barbed tee so I can try it w/o deadheading the pump.

[SLITS]

Thanks everybody. I found that itty-bitty tee, but having no connector to screw into it, I tried the barbed connection into the rubber fuel line. Gotta cut it and find a barbed tee so I can try it w/o deadheading the pump.

You don't screw anything into it. Take a section of 7 mm hose (normal fuel line size), slip it over the nipple and use a hose clamp to secure it. It won't blow off.

Oh, the other end of the fuel hose goes to your guage. If your guage has a 1/8" NPT inlet, you can screw it into the 7 mm hose and secure it with a hose clamp.

[Donaldo88]

Wow that was really stupid of me not to think of just hooking hose to the fuel rail instead of looking for a threaded connection. Got 35 psi. Yes, I can blow through the return hose and hear bubbling in the tank.
The diagram in Haynes was really confusing because they left off cylinders, fuel rails, direction arrows, and labels, and I was confusing the regulator with the cold start valve. There is only a regulator on the driver side.
So with the help of Dave and Tobra at Pelican and SLITs and Dave at 914 club, I got re-motivated after letting it sit for weeks.
So the symptoms were that after sitting a few weeks while I was dealing with the alternator belt, it ran about 6 miles, started sputtering and farting, and died. Sat overnight and started again, but sputtered worse and worse the 2 miles back home, and I pushed it into the garage, then I started my fuel system research. I may have done it to myself by putting Chevron Techron in the tank, AND a new fuel filter, to clean up the system in preparation for the 10% ethanol gas being sold now in NH. The timing indicates that. This method was recommended by a mechanic for older cars.
So if I have a free return, is there any other diagnosis BESIDES PLUGGED INJECTORS? (no Tobra, it's not a drivability problem it's STARTability, so I'm not thinking air leaks for the present, but thanks for the tip)
Thank you all.

[mnementh]

Donaldo,
I know this may sound silly, but I have experienced the same thing myself on a 75 1.8. Check your Cylinder Head Temperature Sensor, the number are in Haynes. This sensor leans out the fuel mixture and the car just will not start if is is an open circuit. Mine went bas during the Porsches to Oxford drive, and it missed, popped and bucked really bad. The other thing that I had an issue with is the flap in the air box. The guys here (correctly) suggested I check the resistance of the pot attached to the flap (which turned out OK), but in the process of moving the flap with my finger, I found places in the travel where it was sticking. I had to take it apart and grease the pivot points and get it moving smoothly. Hope this helps.
Roy