L300 start problem. Glo plugs cycle instead

[JHelzer]

Hey, wanted to pick your collective minds.

First off, this is a transient problem. Happens and then does not repeat for months. Only happens when the engine is warm, ie, I have shut down the van for a few minutes and want to re-start.

I've spoken to my mechanic and he is hesitant to start ordering parts and charging me all sorts or labour to chase down an electrical problem that hides like this one.

I have a '92 L300 and there is a manual glow plug switch installed. On a normal start, the manual switch is used to activate the 24v glow plug relay. After start, the 12v relay clicks over several times until the engine is happy.

When the problem occurs, the manual switch stops working (the 24v relay is disabled) and turning the key to start just starts the 12v relay cycling and does not engage the starter.

I imagine that the 24v relay is automatically disabled in conditions that the 12v relay is in use. My thought is that the 12v relay is confused and thinks that the van is running which kills the 24v relay and prevents the starter from engaging.

After 30 minutes of cursing and wiggling wires and looking around, the van always decides to start normally. Something resets, maybe a solenoid relaxes, after the van cools a bit.

Anybody have an idea what the culprit might be?

Thanks

John

[jelbon]

You're going to have to be a bit more specific on how your manual system is wired.
Is it just bypassing the ignition switch?
Or is it eliminating the glow plug controller and using the relays?
Or have you wired directly to the plugs?
There is no 24 volt circuit, just 12 and 6.
The starter relay is located right beside the glow plug relays and the wiring may be messed up there by however the manual switch was wired.

[JHelzer]

Okay, guess my terminology is off. The manual switch is wired directly to the one glow plug relay, the second one from the outside. Next to the two cylindrical relays is a rectangular relay, this is the starter relay?

When the problem occurs, the rectangular relay is the one which is clicking.

The switch was installed when I purchased the van so I cannot say exactly how it was done.

John

[jelbon]

I think you just have a bad starter relay, that only fails when it's hot.
The only way to test it is to check the terminals for power when it occurs.
There are a few threads relating to this, just do a search to find them.
There's also an excellent thread regarding the glow plug system operation in great detail.
I bypassed the entire glow circuit using a manual switch, circuit breaker, solenoid and 11.6 volt glow plugs. It has worked fine for 2 years now.