mbz

OK I think I found the problem..... clogged fuel return line (the metal one under the car - I tested the rubber fuel return line 2 weekends back and it was fine.). Follow this to see if I am correct. 1) Removed the FPR. 2) Clamped off one of the fuel input lines on the fuel rail. (the right side closest to driver) 3) Connected a 50 psi fuel hose to the return line where the FPR fuel return would go. 4) I blew into the return fuel line hose that I hooked up. 5) After about 50 seconds it got more difficult to blow into the fuel return line and I noticed air coming back from the fuel return line 6) About 10 seconds later, gas started flowing back from the fuel return line (almost like a siphon). I clamped it off so it would not keep gushing fuel out. I am guessing it would only be as much fuel as was in the return line to the tank where the clog is. If that's the case I would venture a guess that the clog would be about 1/3 to 2/3 down the metal line based on how long I blew into the return hose. let me know if this is the correct diagnosis.

DaveWM, what about a set up like this....? And, if this will work, let's make sure I understand the test and the potential results. Without the FPR in the way of the fuel return line, the unrestricted fuel flow should go right back to the tank and the fuel pressure on the gauge should drop. If the fuel pressure does not drop, then I have a CLOG somewhere in the metal fuel return lines going back to the fuel tank, which is causing the high fuel pressure. Do I understand this correctly?

OK so I'm getting a little twisted up here..... Should I focus what is left of the time today to trouble shoot this on checking for a clogged return line? Or should I focus on testing the vacuum at the FPR and the manifold?

Is it possible to just use a plastic T with hose barbs? Like something from a plumbing store?

You mean something like this diagram?

OK so if the return hard line is plugged up, how do I clear it out? Why not just test that and clear it out? This would eliminate the clogged return from the puzzle. It seems that I would want to disconnect the fuel line going into it and coming out of it, then flush it out with something? Or is there a snaking wire I could run down the length to clean it out?

Correct me if I'm wrong, but isn't there supposed to be an anti-stall dash pot right there?

OK so maybe I should get a vacuum gauge and test the vacuum AND, get a vacuum puller to pull the proper vacuum on the FPR to ensure it is functioning properly? IF the proper vacuum is applied to the FPR and it functions properly AND the fuel pressure goes down when proper vacuum is applied to FPR, then it stands to reason that there is a vacuum leak somewhere causing the FPR to not function properly. At that point it seems that checking vacuum at various points will give more info as to if and where a vac leak may be present. Regarding the fuel pressure gauge, I'm not defending it, however at worst I think it's maybe 1-2 psi higher than it should be. That last set of fuel pressure data was pretty consistent (albeit high).

JONATHANRUSSEL: Yes the AFM flapper moves easily. ZED HED: I ran a set of 10 tests and got consistent results: Fuel Pressure Engine Idling: With Vac. Connected to FPR: 41 psi (every time) Without Vac. Connected to FPR: 44 psi (every time) I did not think of trying it with the hose clamp to prevent vac leak at manifold, but will try that next. <------------------------- START SIDE NOTE -----------------------> I am starting to believe that the PO's Mech may have adjusted the AFM to pass smog (his notes state that he "leaned out" the mixture when trying to pass smog.... but this does not explain why the car is running rich). Take a look at these videos.... the first one shows the AFM while idling WITH the Vac hose connected. The second one shows the AFM WITHOUT the Vac hose connected. Also, when the vac line to FPR is connected, if I hold the AFM flap in position (lining up the white marks) and do not let it fluctuate, the idle returns to normal and the fuel pressure drops to 34 psi (acceptable level). However, when I let it go, the pressure rises back to 41 psi and then the symptoms return (rough idle), fuel pressure rises, and then engine dies. <------------------------- END SIDE NOTE -----------------------> AFM_idle_with_Vac_hose_connected..MOV AFM_idle_without_Vac_hose_connected.MOV

I also took the lid off the AFM, it was silicone sealed shut. It looks like some of the silicone sealer stuck to the metal coil on the upper right side. (see photo #2) Anything look wrong with the AFM?

You mean like the clear plastic connector in this photo?

I get it, sort of. Re-run the fuel pressure tests several times to "try" and get consistent data. However, only do it with the vac line to the FPR open or closed..... yes? If so, do you think this rig will work to quickly check fuel pressure with vac and without vac? (see photo) Where the VAC is open (or ON) if the hose clamp is open and the VAC is closed (or OFF), if the hose clamp is closed.

You mean something like what I drew in this picture?

It is possible, however the PO's Mech's notes indicate that the injectors were re-sealed with new mount holders and all fuel hoses replaced in July of 2018. Point being, it's not like It's a 40+ year old fuel rail that has not been serviced recently.

I'll give this a try. How many pressure readings do you think is sufficient? 10 on 10 off? More? Less? I'm going to go hook up a longer hose.

Can I just put a valve in the vacuum line between the manifold and the FPR so I can get quick readings without having to replace the hose every time? That tiny hose is a PITA to get on and off and tears frequently.

ditto  OK I just did that and there is vacuum present, although I do not know how much. The engine seemed to idle better when the vacuum hose was disconnected. Fuel pressure was still very high (40-42 psi).

Both good points, and no I have not checked either yet. Was focusing attention on the electrical (spark plugs, battery, ignition coil, distributor), and fuel delivery (fuel filter, fuel pressure, fuel flow to return, etc). I'm really starting to think the vacuum leak theory has some credence. The engine is getting too much fuel and the fuel pressure is too high. The return fuel lines are functioning, and the FPR has been replaced with a new one, yet fuel pressure is still too high. The engine is confirmed running rich (new fouled spark plugs and taking oil cap off valve cover have confirmed this), and it is not getting enough air AND/OR getting too much fuel because FPR is not functioning properly due to no/weak vacuum. Which leads me to believe that there is a vacuum leak somewhere in the air intake system that is substantial enough to cause the FPR to not function properly. So for today's round of diagnostics I am planning on the following: 1). Check the vacuum at the point where the FPR vacuum connects to the air intake manifold. 2). Inspect and test EGR Valve (apply vacuum) and solenoid for proper function. 3). Disconnect and inspect the hose that connects the AFM & TB. 4). Check TB flap to make sure it is functioning properly. 5). Perform visual inspection of intake manifold for any obvious signs of wear / damage that could result in vacuum leak. Am I missing anything from today's list of diagnostics? Does this seem like a reasonable / logical next set of tests? If so, I need to head over to HF and pick up some test gear (vacuum gauge, vacuum puller / brake bleeder, inspection mirror) pronto so I can get started.

Good questions..... 2 weekends back I checked for blockage in the fuel return line. With the pressure gauge inline after the fuel filter, I disconnected the fuel return line where it connects to the metal return line running back to the tank, and drained it to a bucket. While the engine was running and the fuel return was draining to a bucket, I looked at the fuel pressure gauge and there was no change in the fuel pressure. If I understand this correctly, this tells me that the high fuel pressure is not a result of a clogged fuel return line since the pressure was still high (40+ psi) and the fuel return was functioning properly. My question is this...... Would a large vacuum leak at or near the air intake manifold cause the engine to get too much fuel, thus resulting in running rich and ultimately flooding and stalling? It stands to reason that if there is not sufficient vacuum present from the air intake manifold, then the FPR would not function properly. Any thoughts on this theory? I'm trying to determine where to focus my diagnostic efforts.

I'll pick one up (brake bleeder) tomorrow and test the FPR. Again, that's why I want to talk to the POs Mech and find out what his notes meant in regards to the "leaking vacuum".

I'll pick up a vacuum gauge and a brake bleeder (can pull a vacuum) as well tomorrow. I'll need them both anyway and HF is having a big sale. Should be able to get them both for about $30 bux including tax.

Yes it looks pretty simple, and probably best to inspect anyway. However I am very keen to find out what the "leaking vacuum" was that the PO's Mech referred to in the last repair notes from July 2018. I'll put a call into him tomorrow AM and see if I can get any relevant info.

OK re-reading service records from PO's mechanic as to the last work done on the car. Service notes state: "reseal fuel injectors, replace mount holders and all fuel rail hoses - leaking vacuum and fuel cold" (it ends abruptly but I'm assuming this means fuel cold start valve - but not sure) It further states: "reseal thermostat upper housing" I think a phone call to the PO's Mech is in order to get some clarity on the "leaking vacuum" that was repaired.

FPR to Manifold EGR Valve Solenoid to EGR Valve: EGR Valve Solenoid to metal line going to throttle body: Other end of metal line from EGR Valve solenoid: Vacuum line connected to Throttle Body: From the throttle body, the vacuum line connects to a " T " which splits it to the distributor and also to the charcoal canister.

Not sure I follow......