ignition problem

[Wannabay]

I have had a deteriorating 'hot start' problem for ages ie starts OK from cold but thereafter no joy; turning key meets with an eerie silence, no 'click, nada. As a fall back I have a 'hot wire' to the solenoid/starter in the engine bay with an inline fuse holder, so turn ignition on to position that oil/gen lights up, nip round to back of van, insert fuse in holder, starter kicks over, engine fires up, take out fuse - fail safe works every time but it's becoming a bit of a drag. Last w/e I put a new transmission earth strap on, cleaned the battery earth strap where it earths to van and checked connections to solenoid. This has made matters worse as van won't even start from cold on the key, but fail safe is fine. So I guess the solenoid/starter are OK an dthe problem lies either in the ignition switch itself or the near 40 yr old wiring - it's a july 1971 RHD. How easy/difficult is it to swap in a new switch? Am not sure if it's a steering wheel off job or not. Presumably I could get the new switch's internals adjusted so that it works on existing one key? If it's not the switch then it's the wiring. Problem here is that van has belly pans so I can't run cables under the van so would have to run up and along side of floor to switch and back again.
Any help/ideas?
Am off for a long w/e, by train unfortunately, but will crack on following w/e
cheers
gerry

 

[Bookwus]

Hiya wanna,

If I'm going over territory below which you already understand, my apologies.........

It takes about 9 to 9.5 volts to kick the starter solenoid. In an ideal system (no corrosion, everything hooked up properly) your battery should be putting out just over 12 volts. That 12 volts from the battery has to to travel up to the ignition switch and all the back again to the solenoid. The problem here is that this system works quite well as long as everything in the system is within operating specs. After 40 years there's a lot of room for problems.

Much of the problem occurs in the wiring between the battery and the ignition switch and the switch and the solenoid. Corrosion, dirt, crud, loose connections can all drain voltage between the battery and the long trip to the solenoid. And this is assuming that the battery is putting out 12 volts which it may not be. And now we arrive at the solenoid. The solenoid is really what makes up the hot start (it should really be hot no-start) portion of the problem. It too gathers corrosion, dirt and crud which make for more friction on the plunger pin. Add in the expansion of heat and moving that plunger pin will require more than 9.5 volts to engage. So, while you may be able to start the Bus when it's cold, the heat of operation has effectively locked your solenoid up. You need more voltage at the solenoid.

You need to go through the wiring and polish those contacts. ANY contact point in that ignition system should nice and shiny. In addition Bosch recognized (quite a long time ago really) that this was an inherent problem in Bus (Bugs too can suffer from this) design and so designed their WR-1 Low Voltage relay kit for just this situation. I'd suggest that you look this up - it will cure your problem.

 

[Araon]

as above, spend a quid on a fibre glass pencil and polish your contacts you may as well go through the fusebox while your at it.......