by passing glow plug controller on 6.2

[kidatheart]

I bought an old '84 GMC with a 6.2 diesel. I really don't know what I am going to do with it, but I don't want to put any money into it right now, but I would like for it to start easily. The glow plugs don't work, and I think it is the controller. Is there an easy way to bypass it or "jump it", like you can do on a starter solenoid? Then put a toggle switch on it? Thanks for the help. Doug

[Tiger Joe]

I think the 6.2 is just like the 6.5. You can put a button in to bypass the relay. I wouldn’t put a toggle switch I’d use a push button you have to hold on.

[Dannyboy1966]

Originally Posted by kidatheart

I bought an old '84 GMC with a 6.2 diesel. I really don't know what I am going to do with it, but I don't want to put any money into it right now, but I would like for it to start easily. The glow plugs don't work, and I think it is the controller. Is there an easy way to bypass it or "jump it", like you can do on a starter solenoid? Then put a toggle switch on it? Thanks for the help. Doug

From the looks of the wiring diagram it can be done, but I'm no expert, maybe someone else will chime in on this that knows more about the diesel glow plugs. Good luck Doug.

[kidatheart]

The push-button is a better idea. Thank you.

[hatzie]

The 84 system is a thermal timer in the intake that drives a golf cart contactor.
You can drive the contactor with a push button just like a Ford starter relay.
If you are not very very very careful you will burn out any glowplugs that aren't already crispy and swelled up. I've had to pull the heads off a truck that had all eight AC 11g plugs swelled up and stuck so I could pull the prechamber inserts and remove the swelled tips that way. Not fun at all.

Your other option is to use a 1985 and later 6.2/6.5L glow controller/contactor... they cost about $35. The time to wire the newer contactor up will be your largest cost in the project.

There are five connections to the 1985 and later glow plug contactor/timer # 12015982 Metripack 280 four position plug. You can rob all but one off the old controller.

1. --
2. Starter Glow Inhibit ( hook to the Purple CRANK wire on the start stud on the starter solenoid )
3. Glow Plugs Active Sense ( wire to the glowplug contactor output stud on the controller [Green off the output stud of the 1984 glowplug contactor] )
4. Power ( Hook to the Brown Ignition Power wire from the 1984 Glowplug controller or tee into the injection pump fuel cutoff solenoid connection )
5. Ground ( Hook to both black ground wires from the 1984 Glowplug controller or run to a good ground )

The two big posts on the 85 and later controller are incoming Battery power and output to the glowplugs from the big posts on the 1984 glowplug contactor. Just move the wires from the old contactor to these studs.

I would highly recommend replacing all eight of the old AC Delco 9G or 11G "slow" glowplugs with AC Delco 60G PTC golwplugs or PTC aftermarket glowplugs before the old ones swell up and make changing them an all day ordeal.

[kidatheart]

Thank you for your reply, and all of that information. I am pretty sure I am going to part this truck out, so that I can use the running gear. But I may use it around the house for a while first. That sounds time consuming. If I just wanted to put a push button in it for now, where would I wire it in at? Thank you.

[hatzie]

EDIT... Looked at the wiring diagrams rather than relying on my memory... The contactor has a small gauge Light Blue activate wire. Feed that wire a Ground and it'll close the high amperage contacts.

This will not fix dead and swelled up glowplugs and you will burn out the remaining glowplugs pretty quickly without a timer if they are not changed out to AC60G PTC glowplugs.

The 6.2L will not happily start below 50°F ambient without glowplugs. I've bought several 6.2L trucks with "bad engines" that someone installed a pushbutton on the glowplugs that burned out and swelled up all eight. I installed the later controller and new PTC plugs and did no other significant work and they easily started at -20°F.

[44th Miss Inf]

To add to the 85-93 controller, with 60g plugs, add a 5 ohm, 2 watt resistor in the wire going to pin C on the controller and it adds 4-5 seconds of glow time (mine is now right at 10 secs) which is needed with the 60gs.

My truck has been set up this way for at least 15 years with no issues

[kidatheart]

Thanks to all for the information.
That's why I like this Board-there is a world of information out there, and so many have it, and are on this Board. Thanks again.

[hatzie]

I never did the resistor mod.
I just turned the key off and on after the WAIT lamp went out to cycle the glows twice... I got used to doing that on the VW 1,471CC & 1,588CC diesels in the Rabbits and the habit stuck...

BTW the 1994-2002 glow controllers only have three wires on C-E. GM decided to dispense with the CRANK sense after 1993. It's a good excuse to use the BROWN wire from the 78-84 controller... it doesn't stay powered when cranking. The injection pump fuel cutoff power stays live while cranking.

[kwmech]

Push button is easiest. BUT, the controller is a grounding circuit. So one side of the button has to go to a good ground. When you turn the key on the ignition powers the glow plug relay, then the controller grounds it making the contacts close. So just ground that wire with the button. Only need to hold the button for about 5 second intervals to prevent blow out on the tips

[44th Miss Inf]

The 60g plugs are self limiting if you go with them, but they do take more time to heat up, hence the reason I specified them in my post.

There was a test done years ago with a new 60g where it was hooked directly to a battery with a charger on it and run for 6-8 hours straight with no swelling or loss of color/heat intensity.

[kidatheart]

Originally Posted by kwmech

Push button is easiest. BUT, the controller is a grounding circuit. So one side of the button has to go to a good ground. When you turn the key on the ignition powers the glow plug relay, then the controller grounds it making the contacts close. So just ground that wire with the button. Only need to hold the button for about 5 second intervals to prevent blow out on the tips

So I would run a wire from a good ground to the push-button switch. On the other side of the switch, where do I go on the controller to make it ground the contacts?

[kwmech]

Just unplug the controller and forget about it. Go directly to the glow plug relay itself on the inner fender. You can either cut the wire there or splice in. On the face of the relay there is a connector with 2 wires. One pink and one black or blue. You want the black or blue wire. Follow the harness towards the firewall and you will see a 6 way connector with the wires in it. You can cut or splice it there. When you turn the key on, the ignition will throw voltage to the pink wire and the controller and the thermal sensor would ground the black or blue making the relay work. Make sense? So just unplugging the controller deletes the circuit and you complete it when you want by just pushing a button

[kidatheart]

Originally Posted by kwmech

Just unplug the controller and forget about it. Go directly to the glow plug relay itself on the inner fender. You can either cut the wire there or splice in. On the face of the relay there is a connector with 2 wires. One pink and one black or blue. You want the black or blue wire. Follow the harness towards the firewall and you will see a 6 way connector with the wires in it. You can cut or splice it there. When you turn the key on, the ignition will throw voltage to the pink wire and the controller and the thermal sensor would ground the black or blue making the relay work. Make sense? So just unplugging the controller deletes the circuit and you complete it when you want by just pushing a button

Sounds simple enough. I can cut the black or blue wire by the 6-way connecter, connect a wire there and run it into the cab to a push-button switch. On the other side of the switch, run that wire to ground. Correct?

[kwmech]

Yup, make sure it is the correct wire, I was doing that off of memory

[kidatheart]

Originally Posted by kwmech

Yup, make sure it is the correct wire, I was doing that off of memory

Thank you. If the weather and my wife ever get better, I am going to give it a try.