'77 FI stalls and dies while driving

[GreenFootprints]

For about 4-5 months I've been dealing with intermittant stalling, shuddering and occasionally the engine turning off completely while driving. When it happens, all of a sudden the accelerator will act almost like a break when depressed, and then the dash lights will come on like I've turned the key to on before starting it, but haven't turned the engine over yet. Because of the symptom with the accelerator, and because replacing the fuel filter tended to solve the problem for a couple weeks a a time, I assumed it was a fuel delivery problem. I replaced the gas tank and fuel lines (and sender, which had stopped working for months, but is likely unrelated), which were full of rust and gunk, and re-timed the distributor (electronic ignition), which was a few degrees off. Ran like a dream for about 2 months, so I thought the problem was solved. Now, its back in full force, stalling hard and dying while driving. Sometimes it will restart right away after it's cut out, other times it takes 10-15 minutes or longer before it will start again, just as before. I'm a little at a loss of what it could be-- my 2 best guesses at this point are the pump, which does fine if I run power directly to it (and have pretty good fuel pressure when I test it, but that won't tell me if there some intermittant problem or a bad electrical connection), or a faulty temp head sensor, which also seems unlikely due to the intermittancy of the symptoms. Would love some ideas or input if anyone has any!

[Wildthings]

The dash lights coming on while the engine was still spinning would indicate some form of electrical problem, not sure what kind of electrical failure would cause this though.

If you have an automatic and the engine just quits spinning then the dash lights coming on would be expected and likely unrelated to your problem.

Check and recheck your fuel injection grounds and other connections. A pin pushed back out of one of the connectors can cause intermittent contact and might have worked fine for a while if the harness has been shifted about.

[GreenFootprints]

Wildthings, engine isn't spinning, whole thing shuts off and goes out, then the dash lights come on because the key is still in the ignition in the on position. Like if you were to turn the key to light your headlights but didn't want to crank the engine over.

[Wildthings]

[Tram]

I'm going to go out on a limb here and say that I think you fingered your suspect... the pump.

Best way to tell is with your fuel gauge hooked up to a long hose so you can see what the gauge is doing when this happens. I bet you'll be able to see it start dropping off even before it stalls.

If it doesn't, then you've eliminated it as the issue.

The problem with these pumps is that gasoline cools them- sort of counterintuitive, I know, but you know how cold gas can be if you've ever taken a shower with it. If you've been having to replace filters this means your pump has run starved and overheated.

Don't just jump to it though... verify it or eliminate it first.
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[Greg in GA]

what is your fuel pressure on the rail?
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1969 Beetle
1974 Westy 1800cc FI conversion, L62H

Need a really good mechanic for your VW bus? Consider making an appointment with Colin (Amskeptic) next time he passes thru your area.

[bbrowncods]

Make sure your tank is venting and not pulling a vacuum.

[GreenFootprints]

Fuel pump did buzz pretty loudly a lot before the tank was replaced, I assume because it was straining for fuel. It hasn't lately.

[SGKent]

Following a string of good questions by others that led me to ask this - is the tank an FI tank with an inlet and outlet, and was it cleaned professionally before use? What did you do with the vent lines?

Also have you ever monitored voltage at the coil when this happens? A bad ignition switch could cause a problem with intermittent dying too.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Egan Custom Guitars]

Sorry to revive an older thread, but did you ever resolve this issue? I just got my bus back from the mechanics and I think I'm dealing with the same issue. Brand new fuel pump and filter installed along with some other work done.

[Tcash]

FI grounds one on Double relay and two r on top of engine.

Test fuel pump circuit on Double relay.
https://www.thesamba.com/vw/forum/viewtopic.php?t=334340&highlight=

Floaty in gas tank.
Things Found In Gas Tanks

AFM air flow meter fuel pump contact points dirty.
Pump contact

Bad ignition switch. Wiggle the key, engine running.

Transmission ground strap.
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Good luck
Tcash

[Egan Custom Guitars]

Ground wires all look good. I cleaned up my battery terminals as well. The contacts in the AFM box all look clean as well. Pretty rookie here, not too sure how to actually test the Double Relay circuit, but the double relay was replaced last week as well.

[Egan Custom Guitars]

The bus went in for what was projected to be a fuel issue. And we ended up replacing the pump/filter along with 2 of the injectors. The tank was drained of all the old fuel, but I suppose there could be a chance of some larger particles hanging in there.

[SGKent]

is it doing the same thing it was before it went in?
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Egan Custom Guitars]

No, this is a new problem. It fires up and runs great, just seems to have a little hickup. On the 25km drive home, it happened 5 times. 4 out 5 of them occurred when I was shifting gears coming from a dead stop at traffic lights.

[SGKent]

start looking at and wiggling wires while it is running. Might be a bad connection. Also - how heavy is your key chain?
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Egan Custom Guitars]

Just the single key on the chain. I crawled around trying to find something loose or suspicious. Not sure if it would be the problem, but my - terminal on the battery was a loose fit and quite dirty. I cleaned it up and went for a cruise trying to recreate the problem but no issues. Could a poor battery connection have been the culprit?

[Wildthings]

[Egan Custom Guitars]

Just did a 25k trek on the highway and some backroads. No issues after cleaning up the battery terminals, lets hope that was is.....for now