intermittent engine stalling

[kmmcdonald]

I am the original owner of a 1978 Campmobile, which was extensively restored about 12 years ago and has run just about flawlessly since then. I do not work on the bus myself.

For the past few weeks, on a few occasions, when driving it, the engine will lose power for a second or two and recover while it is still moving. There is no sputtering or missing; the engine stops smoothly without drama and recovers just the same. It is as if I had switched off the ignition. Sometimes, this happens with increasing frequency (stall, recover, run for 30 seconds, stall, recover, run for 15 seconds, etc.) until I have to stop. Then, I can restart it, and it runs just fine. It will never do this for my technician when it is in the shop, and he has driven it multiple times for some distance in an attempt to get the problem to occur. He has driven it more than I have, lately. For him, it behaves.

Yesterday, the bus was idling in my driveway, and the engine just quietly and abruptly stopped and did not restart (with two warning lights on) by itself, and I had no trouble restarting it with the key. No missing, no coughing, the engine just stopped. I think that this may be a clue. When I am driving the vehicle and this happens, it has momentum and effectively "push starts" itself to recover, whereas when it was idling at stop, there was no such momentum.

Any ideas?

[Abscate]

Inspecting wiring isn’t sexy but it’s the number one cause of “failure to proceed”

It could be in either the fuel or ignition circuit and it really can’t be diagnosed by symptom. You need someone to put a meter on it and monitor voltages while you drive. I would start with the 12v to the coil

Plan B is start firing the parts cannon.

Ignition switch, fuel pump, fuel pump relays,


How many miles/time on the cap , rotor, points, plugs, wires?
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[VWSunny72]

Lots of things to diagnose, but I had a similar issue and ultimately it was the result of a failing voltage regulator.
Good luck.
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I am owned by a 1972 Westy named Sunny. She has a 1979 2.0L engine w/ dual Weber IDF 40s.

[aeromech]

Have your mechanic hook up a fuel pressure gauge to the fuel rail near #3 cylinder. Open the hatch. Go for a ride while someone observes the pressure
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[Wildthings]

Is it a Federal or California model? Does it have an O2 sensor?

[kmmcdonald]

Thanks all for the suggestions, Here are the answers to the questions:

I do not recall the last time that the cap, rotor, points or plugs or wires were replaced. Presumably, this was done with the renovation 12 years ago. The only parts replaced since that time that I recall were the ignition coil about 10 years ago, and just several weeks ago, the fuel lines due to an obvious fuel leak. The intermittent "stalling" issue, whether coincidental or not, began on my drive home from the fuel line replacement.

The bus is not a CA model; it has no catalytic converter and it never did.

One interesting observation is that, sometimes after I drive it and it is idling, and I am inside the bus, I can hear a whine from the rear that does not vary with engine speed. My technician says that is probably the fuel pump, but he has not been able to reproduce that issue.

If this is a fuel delivery problem, would the engine stall so cleanly? If it was a fuel problem, wouldn't I expect some misfiring or sputtering before the failure?

[aeromech]

I don’t know. Someone suggested firing the parts cannon. I suggest testing fuel pressure. Which one is cheaper?

Replaced fuel lines = failed on ride home
Whining coming from old fuel pump = might be bad

Maybe some crap got swallowed by the pump during the fuel line change?
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[Wildthings]

Points and plugs need to be replaced every 20K miles or so, other tuneup stuff can go further, but not an indefinite distance. Vacuum leaks could be another cause as even some of the original factory boots and hoses would crack and die before they got to 12 years old. Vacuum leaks could potentially whistle and the whistle could come and go with temperature changes.

[Vetterdog]

I know this is an old thread but I had a similar problem- I would be driving and suddenly it felt as though I had taken my foot off of the gas, but it would pick up again right away. Turns out I had installed a crappy aftermarket fuel pressure regulator that was not holding pressure, and basically fuel consumption would outrun supply so the engine was litterally running out of gas. Found the problem by clamping the fuel line in front of the regulator (in front of the tin) and with engine off, air filter apart, ignition on,- opening air door to activate fuel pump and reading the pressure from a gague attched to fuel rail. Went right up to about 100psi until I pulled the clamp off. When running it showed about 10psi at idle. Hope this can help you, or anyone else who runs into this problem.

[jtauxe]

Boy does that all sound familiar. I chased an intermittent stalling and chugging demon for months, including firing the parts cannon at the fuel and electrical distribution systems. In the end, I found the culprit...

It was the wiring harness. I had it running in the driveway and just had the idea out of the blue to wiggle the harness and see if there was a problem. Indeed, at one particular spot of harness-wiggling, the engine died immediately. I got a new harness from Kyle and am back in business, baby!

See this thread for reference:
https://www.thesamba.com/vw/forum/viewtopic.php?t=632034
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[lil-jinx]

wiggle test,Caterpillar actually has it in their electronic troubleshooting manual.
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[Wildthings]

I have been driving my ancient Dodge Truck with an added wire tie supporting the under dash wiring to keep a wire that powers the instrument cluster functioning.

[mikedjames]

The fuel lines were replaced.. So somebody at the garage probably knocked an almost failed electrical connection. Simple things like the spade terminals on the coil..

I call it "Big hands syndrome."
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