Not starting.. Resolved

[mikeybjettaman]

I am surprised that the ignition unit is earthing to the block when there is a chassis earth nearby.. I guess the distro needs it to be earthed on the block but I can't think why. All other earthing is done through the gearbox to the shell. On a side note, when people replace this with a starter earth, where on the chassis is the best location? I have just temporarly put it to a hole I threaded in the bulkhead but I am not satisfied with that. It will be ok, but not great.

[tonytech]

If VW earthed the ignition amp to the block, why change it?
There will be a volt drop across the engine/gearbox earthstrap, particularly when cranking.
This means that there can be a couple of volts between the van chassis and the engine block.
The output of the hall sensor on the dizzy is sent to the ignition amp, This signal can be disrupted by a poor earth.

T

[mikeybjettaman]

I managed to do a few tests. The carb sounds like it's squirting, I used the timing light to check for a spark and I can confirm a pulse is going down the ht lead although I need to check for a real spark next. I checked the battery earth and found the bolt a little rusty so I chased the threads of the bolt, the hole and cleaned up the connections. It is turning over better but still no start. Next job. .. set up the camera and test the spark performance.
I also discovered the rubber pipe at the top of the filler neck is a bit holey. Good to spot. .

[mikeybjettaman]

If VW earthed the ignition amp to the block, why change it?
T

I'll not change it but it does perk my curiosity.

[mikeybjettaman]

Last night I had a friend around to pick up my battery charger for his T25. I jumped at the chance and with his help we could see it was sparking. With that he suggested some petrol in the carb and sure enough, Rusty kicked back to life. I'm pleased I did all of the work on the earths. It turns over nicely now.
Time to start MOT prepping...