Glow Plugs not working on a 93 K3500

[Acesneights1]

Hey,
It's for my buddy in NY. He says they cycle very briefly but are not staying on long enough to start the truck. I am not familiar with the 93 and the truck is 200 miles from me right now and not running. Can anybody with a 93 post a pic of the controller and where i is because I am going to have to do this over the phone with him and I don't know where to tell him to look. Also does the controller have a coolant sensor ? I can only imagine what could be wrong given how horrible the PO hacked all the wiring. He is stuck right now in NY. Atleast if I could see some pics and send them to him I could maybe walk him through a Manual override for now.
Thanks.

 

[bk95td]

The controller is in the same place as the newer 6.5s. It is a different controller from the 94+. It is the same as a 6.2 controller. Not really connected to a coolant temp sensor. More of a timer/resistance thing.

 

[NVW]

Is it similar to the later ones where if the batteries have been disconnected, it won't go through a complete glow cycle?

Wondering if he had the bats disconnected.

 

[buddy]

Its actually temperature dependent. If the controller itself is hot from radiant heat the time is less. Like bk said, its independent of coolant sensor.

So if its not glowing long enough it could be because the controller itself is bad.

 

[Acesneights1]

OK. I'll try to send him a picture of mine. Do they look the same ?

 

[bk95td]

Yep except one less contact on the weatherpack connector

 

[chevyCowboy]

Its actually temperature dependent. If the controller itself is hot from radiant heat the time is less. Like bk said, its independent of coolant sensor.

So if its not glowing long enough it could be because the controller itself is bad.

is that why some times in warm weather when i go to restart the truck the glows wont cycle at all?

 

[Acesneights1]

IDK, if it's the same as a 6.2 the 6.2 has a temp sensor/inhibitor because when my CUCV is hot the glows will not come on at all but the truck starts right up.

 

[bk95td]

I guess I should have been more specific. The late model 6.2s nbs 88-93 2500hd and 3500. The LDs and possibly older models did have a temp switch on the rear of the passenger side head that somehow connected to the glows and cold advance/high idle. The HD didn't have that temp switch.

 

[WarWagon]

I guess I should have been more specific. The late model 6.2s nbs 88-93 2500hd and 3500. The LDs and possibly older models did have a temp switch on the rear of the passenger side head that somehow connected to the glows and cold advance/high idle. The HD didn't have that temp switch.

This switch in the head inhibited the old 9G's from coming on in a hot engine and getting the white hot tips blown off by the injector spray. Failure of this switch could ruin your engine. Ask me how I know... Some models do not use this head switch.

The 1993 controller has a cranking sense wire. Otherwise it uses it's own internal temperature sensor and timers for the glow plugs. No other connections change the glow time. It will not cycle the plugs after the controller gets to a certain temperature. This is why the fragile electronic device is attached to the head with 2 studs - so it can sense the head temp (and not vibrate loose...)

I would check the ground for the controller and take apart the glow plug power wires to check for corrosion.

After that replace the controller: likely the timer capacitor, a large heavy item on the board, has cracked it's solder connections from vibration and is short timing the plugs. ECM controlled controller do not have this heavy component to break loose...

Jump the controller glow plug connections for 10 seconds with a screwdriver. If that doesn't start it you have other glow plug issues or no fuel...

 

[iamdave0887]

Yep except one less contact on the weatherpack connector

My 6.2 controller has one more contact in the weather pack connector. 6.2 = 4 pin IIRC, but i'll have to check the spare in the shop. 6.5 94+ i have sitting here next to my computer is a 3 pin.

Easy way to tell what controller it is while it's hooked up in the truck would be to go by color of the controller. The 6.2 style controller is gray, and the 6.5 ECM controlled GP controller is black.

IDK, if it's the same as a 6.2 the 6.2 has a temp sensor/inhibitor because when my CUCV is hot the glows will not come on at all but the truck starts right up.

My blazer is the same way, although your cheating with that 24 volt starter:rof:. After a certain temp the glows do not come on at all. That inhibit switch is in the passenger side coolant block off plate. The switch in the rear of the passenger side head is for the cold advance/high idle. There are 2 separate switches. Two totally different circuits.

 

[WarWagon]

Wiring diagram for 1993 posted here.
http://www.thetruckstop.us/forum/showthread.php?8908

EDIT:
Not sure what year that is as my 1993 does not have a cold advance relay...

 

[daustin]

My '93 has the cold advance relay, it's ran through a "switch" in the coolant crossover. The switch turns off the cold advance at 140F, high idle as well.
Don