Hot Start and Bucking Problem

[drober23]

'75 Westfalia with a 2.0L engine ('78 FI system).

I have been driving the bus a lot this summer. Including about 2,000 miles over the last two weeks. Three trips from around Detroit to around Pittsburgh

On the 1st trip, about 220 miles into the trip, I got one "buck". It was like the engine cut out for 1/4 second. Then the bus continued to run flawlessly the last 30 miles of my trip. I cleaned the grounds in the engine compartment, and around the starter and hoped for the best. I have a air fuel meter hooked up currently. The air fuel ratio did not change until the engine actually cut out. This leads me to believe it is ignition-related, rather than fuel pressure related.

On the return leg of the 1st trip, the bucking started after about 100 miles. It was just a few at first. About 180 miles into the trip it increased in frequency and duration. The engine would act like it was cutting out for a couple seconds at a time. Eventually, it stalled out completely. At this point the starter would not engage at all. It was late, and I had my 8 year old with me, and I have AAA plus, so I called a tow truck and had it towed home. When I got home, the starter did not engage when turning the key. It still did not start the next morning.

I swapped a starter in from a bus that has not displayed a hot start issue in the past. Cleaned all the engine and starter grounds (again), and inspected (but not cleaned!) the transmission strap. Bus started great. Drove it to work all week (about 200 miles worth), and hoped for the best.

On the second trip, I had a hot start problem if I drove the bus over an hour. No bucking though Oh the third trip I had two more instances of "buck" on the way there (both about 1/4 second long), but no more. Still have the starter problem though, even after rest now.

Here is my initial diagnosis plan. Please add any advice you may have for me:
1) Remove the transmission ground strap, inspect, clean, and re-install (unless it looks rotted)
2) Test the voltage at the solenoid with the key turned to start (trans in NEUTRAL!)
3) Consider disassembling and lubricating the solenoid (I think I have a spare to practice with)

I would like to avoid a hot start relay. Am I missing something obvious? Wish me luck!

[sped372]

Bucking while running and trouble starting are two separate issues. Are you aiming to tackle the starting issue first and then see if the bucking persists? Are you running points? A flaky connection there (or to your coil) can cause intermittent bucking, too, not just the ground strap.

[zabo]

yes ive had a bad coil cause this before

[drober23]

Yeah, I do have two issues that are only tenuously related.

I am focusing on the starting issue for now, since it has went from a hot start to a "lots of the time start" issue. The bucking only happens after I have been driving for a long time, and I won't drive the bus that long at once again for a while. Not sure what to do with that, but I hope the general cleaning of grounds and such will help.

I have Petronix instead of points to answer that question from above. The coil is relatively new (8,000 miles, and one year old), bosch blue coil. Haven't had time to do much yet, as my wife's Saturn has decided it needs my attention more at the moment.

Thanks,

[drober23]

I tested the voltage getting to the solenoid today with the engine cold. Disconnected the red/black wire and my helper engaged the key. The reading was 11.7 v. Reconnected the red/black wire and had my helper turn the key. The reading was 11.9v and the starter engaged.

My plan is to test this voltage again the next time I am in a no-start situation. This should let me know if I have an electrical problem that only shows itself when hot, or if the solenoid needs more juice to fire when it is hot. Is it common for the voltage to deteriorate when the wiring gets hot?

[grandfatherjim]

It is common for the solenoid to want more current when it's hot, and since current it has to travel from back, to front, to back again, through perhaps crusty contacts in the ignition switch, it is common to see a low enough voltage at the solenoid that it won't engage. It's not that the wiring is hot but that the solenoid is being cooked by the hot air coming out the flapper valve.
I'd go for changing the ignition switch wiring harness. Maybe that's related to your other problem too.
Jim

[drober23]

I'm afraid that is what the answer is. Going to do a few more things before following that one up.

Although, could a faulty ignition switch cause intermittent lack of the "run" signal? Hmmm...

I think my next steps are to clean and lubricate the solenoid (hoping to reduce the current it wants), replace the transmission ground strap (it looks a bit crusty), and replace the TSII (on principle, but I think I will keep it as a spare, always want a spare one of those anyway).

If that doesn't take care of the problem, the switch surgery is probably in order. Bleh.

[Amskeptic]

I'm afraid that is what the answer is. Going to do a few more things before following that one up.

Although, could a faulty ignition switch cause intermittent lack of the "run" signal? Hmmm...

I think my next steps are to clean and lubricate the solenoid (hoping to reduce the current it wants), replace the transmission ground strap (it looks a bit crusty), and replace the TSII (on principle, but I think I will keep it as a spare, always want a spare one of those anyway).

If that doesn't take care of the problem, the switch surgery is probably in order. Bleh.

You have an Itinerant appointment to share the bleh with . . .
Colin
(p.s. update your list for us via PM. With the 1,267 Volkswagens on your property, we need to carefully determine which ones we shall focus upon)

[drober23]

Progress!

I replaced the fuel filter and transmission ground strap, then took the bus for a spin. It cut out for an instant within a mile. Guh!

I drove a couple more miles, with just one more hesitation. Then, on the way home about 2 miles from my house on a side street, it cut out completely. As I coasted to a stop, I tried to restart (ignition on, clutch in gear, moving...) but nothing. I pulled to the side of the road. Starter worked, but no attempt to fire.

So, I looked in the engine compartment thinking that I didn't really want to walk 2 miles home and get my wife to help me tow it home. I wiggled the coil connections and the ground connections for the FI (that I have cleaned and re-connected at least 5 times) and something caught my eye. The wire from the fuse in the left rear corner (brake light line) had a piece of electrical tape on it.

I immediately thought to myself: "That shouldn't be there... I don't remember it being there... WAIT! I DO remember!" Flashing back to another not-so-happy occasion... One day I was driving (without my fan screen, shhh!) and the bus died on the road. The wire and fuse assembly had been sucked into the fan and the wire was severed. I did a quick repair and drove home, then promptly forgot all about it.

I not only did a quick repair, I did a poor repair. I simply twisted the wires together and taped it up, probably figuring that I would do a proper repair later. Well! It's later! I took the tape off, cleaned the wires a little and twisted them back together. Started right up! I'll solder them together and cover it up with some shrink tube tomorrow. Here's hoping that has been my problem with the bucking.

I'll report more in a couple days.

[dtrumbo]

The wire from the fuse in the left rear corner (brake light line) had a piece of electrical tape on it.

Actually, that's your reverse light line and it gets it's power directly from the poor coil that's desperately trying to keep your plugs a-poppin'! An intermittent close encounter of those twisted wires with your bus' body would certainly explain your issue. Good find!

[Amskeptic]

The wire from the fuse in the left rear corner (brake light line) had a piece of electrical tape on it.

Actually, that's your reverse light line and it gets it's power directly from the poor coil that's desperately trying to keep your plugs a-poppin'! An intermittent close encounter of those twisted wires with your bus' body would certainly explain your issue. Good find!

Actually, that's your double relay entire FI/fuel pump relay electrical supply that branches out upstream of the reverse light fuse and goes to the double relay via a black wire.
Colin

[dtrumbo]

That too!

[drober23]

Actually, that's your double relay entire FI/fuel pump relay electrical supply that branches out upstream of the reverse light fuse and goes to the double relay via a black wire.
Colin

Actually, I knew that! Which is why the "That shouldn't be there" thought rang so loudly through my brain at the moment I saw it.

I'll try to put a couple hundred miles on it before your visit next week. If I don't get any more cutting out, we may be able to focus on other things. Like why it doesn't want to idle when the engine is cold, or any of a number of possibilities.

[drober23]

Well, phlegmballs!

Driving home today, the bus cut out completely on the exit ramp of the highway. My newly discovered wire was still making good contact and futzing with it did not help this time.

When I came back 90 minutes later to tow it home it started right up. Next up is driving with someone so that I can put a meter to it when it fails. If I find where the voltage is and isn't it might help. Of course, ideas are welcome!

[Amskeptic]

Well, phlegmballs!

Driving home today, the bus cut out completely on the exit ramp of the highway. My newly discovered wire was still making good contact and futzing with it did not help this time.

When I came back 90 minutes later to tow it home it started right up. Next up is driving with someone so that I can put a meter to it when it fails. If I find where the voltage is and isn't it might help. Of course, ideas are welcome!

Be focused. When the bus dies, you are being presented with an excellent opportunity to narrow it down.
Start with a spark check at the center coil wire. Do you get a spark while cranking?
I would do a fuel experiment next, but you have to be coordinated, a little shot of gas down the decel valve clear plastic tube to the wye where it goes into the intake plenum.
If it fires up briefly, then you can determine that the fuel supply is being interrupted.
Failing fuel pumps can play these games when they get hot.
Colin