Glowplugs work without Control Module

[pacebm]

OK, my glowplugs were not working and the wait light was not coming on. I pulled the glowplug module and was getting started on the TM troubleshooting guide. I had a revelation and took a look at the fuse. It was blown. I replaced the fuse and started the truck without the GPM card inserted. It started fine. Shut down the truck and inserted the card. Again, everything worked as it should.

How did it start without the card in place?
Did I damage anything by starting it without the card?

I read everything on here about Glowplugs, modules, theory of operation sticky and I guess I still don't understand how it would work fine with the card in or out. When I say fine, I mean all lights worked, wait light cycled as it should.

Somebody, please set me straight.

 

[Warthog]

A diesel will start without glowplugs. The compression of the air and fuel heats the mixture until it ignites. The glowplus help this until the cylinders are hot enough to do it itself.

You didn't hurt anything.

Very simple terms: when you compress a gas, the molecules bump into each other and the tempature rises. A diesel has a high comression ratio, so when you compress the air and fuel, the heat generated is enough to ignite the fuel.

There is more to it but that is the basics.

 

[southdave]

OK, my glowplugs were not working and the wait light was not coming on. I pulled the glowplug module and was getting started on the TM troubleshooting guide. I had a revelation and took a look at the fuse. It was blown. I replaced the fuse and started the truck without the GPM card inserted. It started fine. Shut down the truck and inserted the card. Again, everything worked as it should.

How did it start without the card in place?
Did I damage anything by starting it without the card?

I read everything on here about Glowplugs, modules, theory of operation sticky and I guess I still don't understand how it would work fine with the card in or out. When I say fine, I mean all lights worked, wait light cycled as it should.

Somebody, please set me straight.

From what I understand the end result, after all the clicking wait lights and jiration. It just grounds out the circut and powers up the plugs...

 

[Warthog]

From what I understand the end result, after all the clicking wait lights and jiration. It just grounds out the circut and powers up the plugs...

That's what ithe controller does. It looks at all the variables and closes the ground connection when needed.

That is why you can do a single wire manual switch.