Wont start when warm. Wheres realy at?

[fordsux8269]

My girlfriends family's got an 82 gmc suburban diesel and after it gets warmed up the glow plugs wont come back on atleast the light on the dash doesnt come on. And it wont start, you have to wait for it to cool down before they will work again. They went to the chevy house and they said that it was either a relay or a circuit board. So he bought the relay but prob is is that he has no clue where it goes. Does anyone know what relay this might be and where it is located at?

[john8662]

Welcome to TDP forums!

Feel free to use the search feature above and search the 6.2 forum for articles and threads on glow plug controllers.

If the glow plug controller system is original on the '82 then it will have a separate relay.

The 82-84 glow systems have a complex thermal switch type controller (cylinder shaped on the drivers side rear head) that commands the relay (that handles the amperage the glow plugs consume) to turn on the plugs.

The relay is located on the drivers side fender and is directly connected to one of the battery terminals. The relay is probably NOT the problem in this scenario.

The controller is what can be replaced to help the starting issue (maybe).

A couple of other things come to mind on a hot no-start problem.

How fast is the starter turning over the engine in general? If slow, then the engine will have a tough time starting when hot and no glow plugs. If it's turning over really fast (good batteries plus good starter) and no glows, most time the engine will start. A starter can still work but be dragging, or batteries worn.

Next, the last thing to check/replace that is has a great bearing on hot starting ability is the injection pump. There is a preticular condition that some older pumps (worn, high miles) have, in that the head and rotor in the pump is worn enough to where it won't start hot (when clearances increase due to heat). This shows up only when hot and during starter cranking (lower rpm, and equals lower pressure).

Anyways, start with the simple...

A lil more info than ya wanted first go round right?

Good luck!

[fordsux8269]

Thanx alot Ill try out all of the scenarios and see what works.

[ZZ]

The best & easiest fix for the warm issue is to make the glow plug relay manual. I've had to do this to three 6.2L's and two 5.7L's and one 4.3L. The starters & IP were fine on all of them. They just didn't have enough compression to start without the glow heat.

[Peter J. Bierman]

Had this problem too after the reconstruction of my engine.
turned out to be the pump timing, a little bit more advance of the pump cured the problem.
Might have the timing checked.

Good luck, Peter

[eclipsefence]

The best & easiest fix for the warm issue is to make the glow plug relay manual. I've had to do this to three 6.2L's and two 5.7L's and one 4.3L. The starters & IP were fine on all of them. They just didn't have enough compression to start without the glow heat.

I actually had the reverse problem(well, smae prob, reverse situation). My glow plugs were switched to manual, but I didn't relize it because the button was broke, and the dash light still blinked. My mechanic changed the wiring back, and now they glow when the light goes on, and it always starts.