1972 Bus - Dies At Highway Speed/Average Temp/Long Distance

[Kregol]

Hey folks. I’ve had some recent problems with the bus and was wondering if anyone had some suggestions of where to start looking. Long story, but I wanted to make sure folks got enough info.

72 Campervan.
Dual Webers.
Rebuilt engine around 5 years back.
Tuned up about 10 months ago and runs great around town.
No obvious problems, no backfires, engine purrs.
Pretty mechanically sound throughout.
Distributor cap is clean and secure.
All spark plug wires secure.
No wires visibly detached.
Oil checked and proper level.

Details:

120 miles round trip.

On the way: No problems. Everything great
At Destination: Bus had some trouble starting up when we initially arrived at our destination. After some coaxing it started up and we parked.
On the way home: It started to just die on the highway. Flat road, no jostling, no bumps, 65 mph, engine temps pretty consistent with my “normal” highway driving temps on the VDO.

I would be driving, everything would be great, sounding like it should and all of a sudden the engine would turn off. By turn off I mean it sounded like if one were to push start a bus and leave the key turned off. The engine was turning, it just wasn’t allowing itself to push the bus (makes a fading "burrrr...." sound).

The problem could be fixed EVERY TIME by pressing the clutch in and allowing the bus to coast for around 5 seconds. I would then release the clutch and it would start moving again. We could then drive for around 2-15 min (random length of time) and then it would do it again. I didn’t turn the key off and nothing else was changed.

Nothing I couldn’t handle, just scary as all hell. This type of thing happened once last summer as well, but it hasn’t happened since. I cannot get it to reproduce this effect and it seems to happen intermittently after a long bout of driving.

I would like to stress that this doesn't happen around town no matter how large a pothole I hit so I'm leaning away from a short.

Any ideas?
Thanks in advance for your time.

[Randy in Maine]

I like a bad fuel delivery problem. What kind of fuel pump do you have? How do you have it wired up (if it is an electrical pump)?

So when it dies, go you get good fuel squirt out of the carbs?

[Kregol]

I like a bad fuel delivery problem. What kind of fuel pump do you have? How do you have it wired up (if it is an electrical pump)?

So when it dies, go you get good fuel squirt out of the carbs?

I have to apologize for my lack of knowledge of the inner workings of the bus.

I believe it’s the OG fuel pump. It looks similar to this:

Editors note: The link to the photo and part description removed as they were no longer valid.

I opened it up last summer and cleaned the screen inside (via Bentley). There was no build up on the screen. I also replaced the fuel filters at the same time. Any other way I could verify that it’s working properly?

I’d be willing to try looking into the fuel delivery to the carbs as a next step. Would that by chance be in a section of the Bentley or VW Alive?

[vdubyah73]

Lots of things could cause this. Fuel tank not venting properly until fuel pump can no longer pump against the build up of vacuum in tank. Fuel lines too close to a heat source and developing vapor lock. Fuel pump worn out. Power to coil interrupted by worn out ignition switch and too many keys swinging on it. Worn out spade connectors to the coil. Condenser on it's way out. Points worn out. The fact that it restarts after coasting with the clutch disengaged and restarting when you let the clutch back out would have me looking at the fuel supply, but first I would check the points adjustment because of the hard starting. The rubbing block that rides on the cam in the distributor does wear out, closing the gap, giving a hard start. Someone on here recently had a long road trip and experienced a similar situation. They were able to limp home and it turned out to be a simple points adjustment.

[Kregol]

Thanks for the ideas folks! I'll give it a once over and report back.

[Randy in Maine]

Can you stick your 0-15 psi fuel pressure gauge on the pump outlet and see what it says? I would sort of T it into the carb feed line set up and see if it changes when it all dies out. You probably only need about 3-5 psi in this thing.

[Kregol]

Hey folks. I wanted to say thank you again for all the feedback.

I went through the bus today with some of the suggestions above.
Checked:
Valves
Points (adjust and visual inspection)
Dwell
Timing
Wires to/from coil as well as spades
Inspected fuel lines: I have the fuel line going over the top of the starter and part of the line is sitting close to the transmission, but there’s no real lines sitting directly on something hot.

Everything was in good working order, but it happened again last night after all this. It was driven to a friends house, then parked for 4 hours and then happened 10 min into the drive home and it only happened once.

It's not really crippling my bus, but it's scary as shit to have this happen at 65 and I really do want to get to the bottom of this. I would appreciate some advice on where to start procedure-wise.

Questions:
1.) How would I go about checking to see if the fuel tank is not venting properly?
2.) Is there a way to diagnose a bad ignition switch? (Bentley pages?)
3.) Randy: Are you referring to a fuel pressure gauge? I'll spring for one next paycheck if i can. The hard part would be that it seems to only do it once. I push in clutch, wait, and it’s fine again. It would be hard to get it to die like this when I’m back there.

Where should I go next? Thanks again!

[Bookwus]

Hiya Kregol,

So..........in all the times before the engine was hot when this occured? And this last time it was just warming up?

With the dualies, does it seem like the cutting out just might be coming from one side of the engine?

[Amskeptic]

Wires to/from coil as well as spades

Sounds electrical. Inspecting wires is tricky. They just sit there looking pretty. Try idling the engine and yanking wires gently to see if you can stall it.
Some specific places are:
The black inline fuse for the back-up lights can short and kill ignition temporarily, check to see that the clip doesn't hit a wire coming out of it.
The cut-off solenoid wires can sometimes short at the throttle lever/crossbar lever when you apply throttle.
The ignition switch itself gets wonky, try pressing in the key the next time the engine dies to see if it recovers.
Think creatively and investigate keenly.
Colin

[Gypsie]

Valves
Points (adjust and visual inspection)
Dwell
Timing
Wires to/from coil as well as spades
Inspected fuel lines: I have the fuel line going over the top of the starter and part of the line is sitting close to the transmission, but there’s no real lines sitting directly on something hot…

Also look for cracked wires that can short out against other grounded parts.

How hard is it to pull the fuel pump apart to check the screen? Might be worth a look see, if it's not too hard It may not be there but I wonder about constricted flow. Pre-pump filter, no? Can you see stuff in the filter element?

There's been a couple of nasty tank issues around here lately and I have had crap block the flow and kill it. Rust flakes make nice stoppers.


Gypsieabitstumped.

[RSorak 71Westy]

Sounds like inconsistent fuel delivery to me.

[midatlanticys]

Hey folks. I’ve had some recent problems with the bus and was wondering if . . . .

Kregol, did you track this down?

V. newb neck-out just parroting the others opinion here, but I'd look to fuel starvation as well: plugged filter(s?) or dirt/crud/corruption in the tank at pick-up tube.

My gut tells me depressing the clutch pedal and coasting may act as a pressure relief in the fuel system, which *relaxes* all the pressure in the lines & components, the blockage falls away or is dislodged just enough to restore flow . . . . for awhile!

Good luck

[Kregol]

Hey folks. Thanks for the replies. I haven’t had a chance to buy the fuel pressure gauge yet, but I may have found at least some of the problem.

First: I checked the filters and everything seems to be pretty clear in there, nothing too gunky in the fuel or filter.
Second: I checked the wires by jiggling them to see if I could provoke the problem but it didn’t happen.
However: The last time it happened, I took off the distributor cap and noticed that the inside of the cap is slightly scored where the rotor would be spinning. The following edge of the rotor arm on both sides is also slightly worn.

I imagine that this could atleast be part of the difficulty. I have a new cap/rotor coming in the mail and I’ll check back after it’s on and running.

Anyone have any advice for tightening up the clips? I may just go after them with a pair of vice grips to make sure there’s no play in the cap. (none noticeable though)

Thanks again for the help!

[Gypsie]

I'm dubious....


but hopeful.

[Amskeptic]

Hey folks. Anyone have any advice for tightening up the clips? I may just go after them with a pair of vice grips to make sure there’s no play in the cap. (none noticeable though)

Tighten up the clips by bending them slightly with some visegrips. Oh, and make sure the rotor is fully seated on the shaft. FYI, some Pertronix magnets create the above-mentioned interference.