Who's an Electrician? My Van Keeps DYING.

[Furgonzo]

Hey there. I continue to be plagued by an annoying problem. My '89 1.7 KY vanagon is dying upon leaving the freeway after 15-20 minutes, minimum. She runs great around town and even long distances as long as I'm not spending long periods at high RPMs. On the freeway, I pull off an exit and as I shift to neutral or brake to a stop, the battery light comes on, she dies and won't start up again for 20-30 minutes. I have replaced the fuel filter and lines, checked the cut-off solenoid (audible click with key ON) and checked that there is fuel getting into the system. The tank was off last year for a cleaning so it seems doubtful there is crud getting in the lines. Occasionally, when I try to fire her up before 20-30 minutes, she turns over and over and finally fires up laboriously, sputtering to life, then runs fine. Otherwise, always fires up first try.

Now for the clincher...My van has an ignition bypass that a previous owner installed. It sits in the engine bay fore of the battery tray and, when connected can start the van from the rear as long as the key is ON. Today, stranded for the 3rd time in a few hours, I tried everything to get her started and nothing was working. On a whim, I connected the bypass and POOF - she fired right up. I am no electrical wizard and am still new to the T3. Where does this leave me? It seems weird that an electrical problem would only manifest itself when the engine is super hot, but that's where this leaves me, right?! A bad ignition switch? I'm so stumped, but feel like this is a no brainer for someone with electro know how.
Any suggestions?

Thanks...

[ewenmaclean]

Hello,

if I understand correctly, it seems this switch at the back of the van is a starter switch by which you can crank the van from there? If that's the case and it helps, then perhaps it is bypassing the solenoid making it turn over quicker if the solenoid is not great - that's just a complete guess. Not starting when hot could be IP timing, or loss of compression, or possibly a bad earth connection to the starter making it turn the engine over slower. I suppose it's just conceivable (IIRC you are in Chile) that your fuel might be getting very hot, and you could do with a fuel cooler, but I doubt it.

It would be helpful to know more about exactly how this ignition bypass is wired up to help diagnose the problem

Ewen

[Furgonzo]

Thanks for the reply. The ignition switch is wired directly to the battery and the starter. Two wires. It doesn't make any sense?! Like I said, I'm no electrical engineer, but I understand the basics and it isn't working out in my head. If it was a compression/IP timing issue, the bypass wouldn't make any difference would it?

[BOXY]

The length of the wires can make a difference. Voltage drop is effected by the cross section of the wire and its length Δ V = I · R = I · (2 · l · ρ / A)

Ignore everything else I suggested. I missed it was a diesel. You haven't got an ignition amp.

[Furgonzo]

Personally I think your problem is probably the ignition amp failing when hot. There was a post on here recently about replacing the thermal paste between the amp's circuit and the aluminium heat sink it's mounted on, maybe that would help?

Can anyone tell me where to find the ignition amp? I have searched, but can't find the post referred to here about replacing the thermal paste...

Thanks!

[kevtherev]

You ain't got an ignition amp...

[VWCamperfan]

If you have an ignition bypass wired up in the engine bay of your van and activating this makes it work again, then it has to be an ignition problem somewhere in the original circuit. I would be going for the ignition switch on the steering column.
If I'm reading this correctly though, the bypass is to the starter motor, not the ignition. If this is the case and using this bypass to turn over the starter motor when the original ignition is on works, then I would suspect the original starter switch is loosing the ignition connection when turning to the start position... Still time for a new ignition switch but test it to make sure beforehand.

[Furgonzo]

Ahhh, the saga continues. After several more annoying break downs, I have confirmed that in fact the bypass is not solving the problem. The one time it did must have been after waiting just the right amount of time. What I and my mechanic pal have added to the puzzle is this...the engine is extremely hot when it happens - coolant is raging - and after a brief moment, pouring cool water on the injection pump allows it to start again. When it still will not start and I turn it over, heaps of black smoke, presumably un-ignited diesel, is spewed. I have checked that the cut-off solenoid is working and have even replaced it with an extra to no avail. My friend, who is a T3 mechanic and knows these engines well, seems convinced it's a problem with the IP having to do with a build up of pressure due to the extreme heat of the engine. I have an extra pump we are going to throw on to see if that makes any difference. If this is glaring another problem to anyone - I'd love to hear your thoughts.
Thanks.

[VWCamperfan]

Possibly a higher revving engine could be keeping parts just cool enough to continue running but when slowing down, a heat build up could create something like 'vapour lock'. This is so uncommon and rare in a diesel that I would have thought it very unlikely because the pressures involved and the fuel itself prevent this from happening.
Running out of answers!

[BOXY]

Are you sure you're not looking at this from the wrong starting point? What if the problem is with the cooling system not working properly and that's letting the engine get so hot that its starting to sieze and stall at low speeds?

[Furgonzo]

Entirely likely. Is it possible that a head gasket of inferior quality could be causing substantial overheating? Coolant seems to be boiling coming out of the head when engine is good and hot (20 minutes of highway time). I replaced it recently and all that was available (in Chile) was a custom made jobby that I now recognize as a poor replacement. I'm still kicking myself for not waiting the 2 weeks to mail order something proper - I've since done that and will be replacing it as soon as it arrives. I also plan on pulling the thermo this weekend to test that it is working properly. The dash indicator never seems to get above halfway, only occasionally kicking on the fan in low speed, though it seems to jump quite a bit when the van comes to a stop - still light never comes on. I am still learning about the cooling system, so troubleshooting is a slow process for me. Any suggestions on good starting points would be a huge help...
Thanks

[Oldiebut goodie]

It does sound like a vapour lock due to heat.
Has the water pump been checked? - Has it got all it's vanes on the impeller? These can 'disappear' causing overheating. Is the radiator heating up correctly?