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Bus won't start when warm - coil check?
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telford dorr
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PostPosted: Sat Dec 04, 2021 1:55 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

To check the meter, connect it across the battery. If it reads correctly, then the meter is OK, and you have a power supply problem from the keyswitch. When the bucking happens, does the gas gauge read properly? Does the generator light come on?

If all of that is OK, then it's time to start looking at possible fuel problems.
- when the problem happens, remove the gas cap and see if there is was a vacuum in the tank.
- check any in-line fuel filter for crud.
- check the sock screen on the fuel outlet in the tank for crud or rust.
- carry a small bottle of fuel. When the problem happens, pour a small amount into the carb and see if it then starts up.
- disconnect the fuel line to the carb and stick it into the fuel bottle (above). Crank a couple of turns and see in the fuel level in the bottle increases [have a fire extinguisher handy for this test, just in case...].
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Starbucket
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PostPosted: Sat Dec 04, 2021 2:38 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Starting to sound like you got a bad ign. switch. Try running a jumper from battery pos. to coil pos. and see if that cures it (remove jumper to stop the motor).
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Nicholas D
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PostPosted: Sat Dec 04, 2021 4:06 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Thanks again for the tips. I let it sit for a couple margaritas, called a wrecker and swapped the old condenser back in for no real reason. Fired up and drove fine the rest of the way home. The volt meter did read fine across the battery terminals so think it was accurate when it read zero on coil positive with key turned. No generator light on and the gas gauge reads correctly throughout.

I have replaced the sock filter as well as the two in line filters fairly recently and they both look fine and had fuel in them during the problem. Fuel pressure was consistently between 2-3 psi the whole time as well. I'll check the gas cap for vacuum next time it happens and it's got dual carbs so not sure about adding fuel to the bowls when it happens? I'll also throw a jumper wire and try the battery positive to coil to check ignition switch. Sorry for the ignorance but it does have what I think is a hot start relay where I turn the key on and then mash a button to engage starter, not sure if that matters.

Thanks again for all the help!
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PostPosted: Sun Dec 05, 2021 12:08 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

When checking the timing at 30° at max rpm I notice the pulley mark is bouncing around a good bit, I guess "scatter" when compared to the same situation in my bug. It bounces around at idle and is even more pronounced at higher rpm. On my bug the mark is totally still. Hopefully that makes sense. Could this scatter potentially part of the problem. Thinking about it more last night the bucking and hesitation first appears at high rpm's like right before my shift points. Maybe the mechanical advance (it's an 09 distributor) isn't advancing properly?

I also noticed the orientation of my distributors is different betterment the two. The wires are in the same order but different locations on distributor. Bug on left and bus on right. It's this a problem? Thanks
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PostPosted: Sun Dec 05, 2021 12:34 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

A worn distributor can cause the jumpiness. If you get a little too much advance, it can "ping" and damage the engine. Consider replacing the distributor with a stock Bosch unit.

Depending on the distributor and how the drive gear was installed, it can be clocked differently. If you use a stock vacuum-can distributor, you may have to reset that drive gear position in order to have clearance for the can.
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PostPosted: Sun Dec 05, 2021 12:38 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Quote:
and swapped the old condenser back in for no real reason. Fired up and drove fine the rest of the way home.


is the bounce after the condenser was replaced? The bounce can come from a bad condenser, or can come from many other things. If the condenser was bad it may have burned the new points, and the bounce you are seeing is from that. Inspect them, and if damaged replace them again or try filing them a touch, then reset the dwell. See if that helps.

Also IF YOU REMOVED the distributor to work on it, make sure it is all the way seated. If it isn't, or you accidentally pulled the spring out, that can cause the gear to float on the brass gear and hop around.
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PostPosted: Sun Dec 05, 2021 1:38 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Nicholas D wrote:
The volt meter did read fine across the battery terminals so think it was accurate when it read zero on coil positive with key turned. No generator light on and the gas gauge reads correctly throughout.

Then it's NOT the ignition switch! Consider:
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Note that the black wire from the ignition switch goes to the fuse block supply buss, and then another black wire goes from the fuse block supply buss back to the coil. The fact that the gas gauge and generator light are working normally indicates that the ignition switch is supplying power to the fuse block. I'd check the integrity of the connection at the fuse block of the wire which goes back to the coil. If this connection was loose or corroded, it would heat up during use, and likely get worse over time. This would also explain why it improves after sitting for a while (and cooling down). Also check the fuse block buss bars for signs of overheating or poor connection.

Could get lucky on this...

Note: DO disconnect the battery before removing the fuse block for access, because of the pain in the a.. location of the fuse block. [Personally, I think VW screwed up big time when they moved the fuse block location from the earlier lip-of-the-dash location of the earlier bays to the almost inaccessable location of the later buses. I know that they did it because of the integrated plug-in relays, but still, they could have done much better... Just my opinion.]
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Nicholas D
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PostPosted: Sun Dec 05, 2021 4:02 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

I'll definitely check the wire from fusebox back to coil - thanks for the tip.

I checked across the coil with a different voltmeter again with the key in the on position and got just shy of 12v. The scatter happened before I switched the condenser out and it ran so shitty with the new condenser I didn't even check it at that point - just put the old one back in. The dwell checks out at 47° and the points look nice and clean. I also tried the jumper wire from battery positive to coil positive and key on but got nothing. However, it started right up with the hot start relay and ran fantastic on a short test drive.

I really cleaned the transmission ground strap again as well as all the connections on the starter solenoid, which were pretty filthy. It may be correct but when I was looking for the negative battery ground strap it appears there isn't one? The only cable coming off the negative post goes to the starter. If this is correct I think my plan is to check every connection and make sure they're clean and keep a new condenser, points, rotor and cap in the bus and just switch it all out next time old "one-way" stands me.

Thanks again for all the advice!
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PostPosted: Sun Dec 05, 2021 4:21 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

The scatter happened before I switched the condenser out

Ok - so are you saying that when you had problems, the timing scattered, then you replaced the condenser, putting the old one back in, and you have not checked it again? That the dwell with the condenser that works is 47 / stable, and the bus runs fine with the old condenser put back in?

The chronology is -> is this correct?
Condenser A, ran fine
Condenser B (new) put in during tuneup.
Ran poorly and died when warm
Timing scattered when it would run
Put original condenser A back in
Runs Ok and dwell stable at 47
Have not checked for timing scatter again?
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PostPosted: Sun Dec 05, 2021 5:06 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Sorry, my timeline is getting pretty convoluted. Here it is:

Condenser A has been in the bus for a year and has always had slight scatter. The bucking/hesitation has always occurred while this condenser has been in the bus. Yesterday, when it was starting but running very poorly I swapped out the condenser A with condenser B (which is brand new) and that is when it ran even worse and died all together. I put the original condenser (A) back in and let everything cool off and it started and ran well. Today when I was checking everything over I noticed that the scatter is still there but it ran well (dwell at 47) on my test drive.

I checked the fuse block and did find some indication of overheating so I'll address this next.
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PostPosted: Sun Dec 05, 2021 6:13 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Nicholas D wrote:
..........I really cleaned the transmission ground strap again as well as all the connections on the starter solenoid, which were pretty filthy. It may be correct but when I was looking for the negative battery ground strap it appears there isn't one? The only cable coming off the negative post goes to the starter. If this is correct I think my plan is to check every connection and make sure they're clean and keep a new condenser, points, rotor and cap in the bus and just switch it all out next time old "one-way" stands me. ......

Where on the starter?, and where is the positive cable attached?
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PostPosted: Sun Dec 05, 2021 7:11 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

The picture will explain it better than my ramblings. I would assume that the negative is grounded here? Kind of hard to see because everything is still so filthy but that's it.
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PostPosted: Mon Dec 06, 2021 1:40 am    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

That location for the battery ground, while unconventional, is fine, as the starter is the highest current drawing load on the bus. Needless to say, the trannie ground strap must be functional to power the rest of the bus.

The real battery ground point is on the angled surface of the diagonal brace next to the right side taillight. There's a m8 captive nut there which takes the ground strap bolt.

Do yourself a favor: seeing as how both of your battery cables are black, wrap a little red vinyl tape or install red heat shrink tubing on each end of the positive cable to act as a reminder where they go, and to help keep someone from jumping the bus backwards...
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PostPosted: Mon Dec 06, 2021 7:14 am    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Your bucking issues- Have you checked for vacuum leaks on your carb, intake manifold and at the heads where the castings bolt down?

Vacuum leaks can give symptoms of a bad condenser or a condenser going bad. It becomes more apparent while driving with the engine under a load.

My 69' bug had similar symptoms. I found 1 of the two carb mounting studs was pulling out of the carb body casting, thus the carb wasn't tight anymore against the manifold. Once fixed, it resolved that.

Spray some carb cleaner or ether at the carb at idle and at all the junctions of the carb manifold. Be careful to not start a fire! If the RPMS change, you found a vacuum leak.
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PostPosted: Mon Dec 06, 2021 7:56 am    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Thanks for the idea about a vacuum leak. I've definitely had to chase them down on my beetle before but for whatever reason I hadn't really thought about that with my current bus problem. I'll give everything a shot of carb cleaner when I get home today and see what I find.

I'll also mark my positive battery cable with red - easy enough and better safe than sorry.
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PostPosted: Mon Dec 06, 2021 5:18 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Think I'm (hopefully) getting close to a resolution so with any luck I can leave all you patient bay window forum people alone soon! Found this on the backside of the five wire connector for my ignition. Obviously this is a problem and I plan to get a new connector and replace but do I assume it was a lose connection right there that caused this or could it be a loose, or bare wire somewhere along the line and this is just where the heat accumulated? If that makes sense? Sorry, my electrical knowledge is even less than my general mechanical knowledge, which is saying something as I'm just slightly above inept in that department.

So I guess I need to know what I should do (if anything) before replacing the connector. Should mention all the fuses in the fuse box look intact and fine.

Thanks again
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PostPosted: Mon Dec 06, 2021 5:45 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

that means there was corrosion in the connection. Corrosion equals resistance, which creates heat. Yellow and black is probably the right head light. Another possibility is that the filament broke in a way that made it shorter so it pulled more current than the circuit was designed for. Or someone put a higher wattage bulb in the bus.
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PostPosted: Mon Dec 06, 2021 6:40 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

That wire is black/yellow not yellow/black. It's the X terminal off the headlight switch, going into the T5 connector before becoming a red/black wire.

The black wire to coil uses the fuse box as a junction, but doesn't actually go through any fuses. You can blow all the fuses and a VW will still start and run.

Common VW wiring terminals:
30 - always has power from battery. Usually red.
15 - always has power with key on OR starting. Usually black.
X - only has power when on but not starting. Black/yellow.
50 - only has power when starting. Usually Red/black.
31 - ground/chassis. Usually brown.


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PostPosted: Mon Dec 06, 2021 7:19 pm    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Thank you for that information and what you're saying is that while that is a problem, it is not causing the rough running issues? I will replace the T5 connector but in the interim can I pull/cut those wires out and butt splice them? Only temporarily.
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PostPosted: Fri Dec 10, 2021 8:03 am    Post subject: Re: Bus won't start when warm - coil check? Reply with quote

Nicholas D wrote:


So I guess I need to know what I should do (if anything) before replacing the connector. Should mention all the fuses in the fuse box look intact and fine.

Thanks again
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Like Robbie said that is the X wire to the ignition switch. If that shorted I wonder what it did internally to the ignition switch? I have seen newer switches with contacts that have sunk in the plastic due to heat. This can cause no or intermittent contact through the switch.

Bypass the ignition switch and see if the problem still coours.
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