CUCV Glow plug wiring

[83k30]

Hey guys. I have a 1986 M1009 that I picked up from a local VFD. Since I've had the truck I have replaced the Gen1 alt, glow plugs, and a GM spin on filter mod. The truck came with a manual glow plug switch already installed by the VFD. The truck has been starting and running fine until yesterday. I held my manual relay switch to cycle the plugs, which are 3 month old AC60Gs, and when the truck fired up it ran for a couple seconds and the WIF light flashed rapidly. I let go and the WIF immediately stopped. When I tried to cycle the plugs again, the relay would not click. Found a burnt 20 amp fuse and checked for any loose wiring. Replaced the fuse and the wait light and WIF light came on. When I attempted to cycle the plugs again via my switch, I shorted my 20 amp ignition fuse again. I checked my voltage to my glow plug relay and had 26v. The lead feeding the relay was attached to the 24v bus on the firewall? I started looking at the wiring and comparing it to schematics and pics from Google and changed some of the wires. I now have 12v to the relay via a short jumper from the engine wiring block. The switch is working properly and allowing 12v to pass through to the glow plugs. The truck will not start up and after my attempted wiring fix my Gen1 alt light no longer lights up on my key on position. I could really use some help as this is my daily driver right now. Thanks.

 

[cucvrus]

Check your fuses again. And wiggle the bulb in the circuit board. I think I would check the glow plugs also. Make sure you are getting power to the bottom side of the relay on the firewall when you have the button pushed. Good Luck. Report back.

 

[83k30]

I checked the driver side glow plugs and none of them got hot when I supplied 12v via jumper cables...I'm guessing that I had the glow plug resistor go bad and that killed my plugs. The relay is working fine and the terminals that supply the voltage for the plugs are OK. Did I hurt the Gen1 alt or is it not wired back the the block correctly?

 

[MarcusOReallyus]

I checked the driver side glow plugs and none of them got hot when I supplied 12v via jumper cables...

Did you pull them to verify that?

I'm guessing that I had the glow plug resistor go bad and that killed my plugs.

Possible, but not likely. The common failure mode is that the resistor opens, meaning, it allows nothing through. In order to fry your plugs, it would have to short. But it's easy enough to test. Got a multimeter? If not get one. Measure the resistance across the resistor pack. Resistance should be 0.28 ohms. (TM9-2320-289-20. page 115)

More likely is that your push button method just wore them out from overcooking.

The relay is working fine and the terminals that supply the voltage for the plugs are OK.

When the system is stock (which yours appeared to be before you started moving wires around!), you should see 24 volts at the input from the resistors to the top of the relay, when the glow plugs are NOT operating. When the GPs are operating, you should see ~12v there. Only when the GPs are operating.

I suggest you put things back the way you found them, replace your GPs, and then start troubleshooting following the steps in the -20, referenced above. To get the best our of your beast, replace the GP controller with a new one and run it stock (except perhaps for the GP resistor bypass, which Rick doesn't like. ).

But get it working as stock before you try to modify anything.

 

[83k30]

I pulled the plugs and checked them and they all were bad so I didn't bother to pull out the 4 on the passenger side. I will move the wires back and put new plugs and report back. Thanks for the help!

 

[MarcusOReallyus]

You can get a new GP controller card from http://www.glowplugcards.com/ Made by a well-respected member here, antennaclimber. There is an excellent video on this site that explains how the GP controller works. Make sure to see the "helpful threads" sticky. Lots of very good info.

 

[83k30]

Can you confirm this wiring at the relay and wiring block? I have the 24v feed through the resistors to the relay input. The wiring for the manual switch is the same as before. The wiring block has the 12v supply from the #2 batt (-) terminal. On the same tab I have both alt connections and a red lead that bridges between both tabs on the wiring block. I will have the glow plugs by Saturday and will post back. I appreciate all the tech support as I'm always trying to learn.

 

[83k30]

Hey guys, I put in some new AC60Gs and a new manual switch. The truck is back in action. The only problem now is when I switch the key to run my Gen1 light and oil pressure light do not register. Once the truck is running, the Gen1 and oil pressure lights come on then quickly go out. I checked and the alt output and everything is getting charged.