This is the story of my CUCV 12V glow plug conversion.

[mistaken1]

I installed all new Wellman 070 glow plugs. The truck started just fine one time. On the second attempt at starting all eight new glow plugs burned out (see picture).

The lot of glow plugs was bad, or the glow plug relay pulled in but did not release, or the resistor on the firewall went bad or the controller failed. I will follow the troubleshooting guide this weekend although the controller cycled the plugs on and off during the burnout phase as well as my one after conversion test start. Anyhow this post is just to document the 12V glow plug conversion not the overall troubleshooting issue.


I went to O’ Reilly auto parts and bought an isolated coil relay (BWD P/N: S603 - $48.99), a 175A stud mount fuse (Bussman P/N: BPAMG175 – $5.29), a 72” #4 battery cable (BWD P/N: 08499 - $11.99), a #4 copper lug with a 5/16” hole (BWD P/N: BH143 - $1.29) and ( 8 ) self limiting glow plugs (AC Delco P/N: 60G - $8.99e). I should have used a BM108 lug as it would have worked better with my crimping tool. Also a longer length of battery cable would have allowed neater cable dressing at the batteries.


First things first, I disconnected the front battery negative cable and the back battery positive cable.

I removed the wires from the original glow plug relay. All the terminals were like new and needed the gunk cleaned off but they were not damaged or corroded. I installed the new relay; it bolted right in place of the old one without modification. I coated all of the terminals with dielectric grease and reconnected all of the wires in the same places except for the 24V feed from the resistor pack.

I insulated the 24V feed terminal by using a layer of sticky-side-out vinyl electrical tape, then a double layer of linerless rubber splicing tape followed by a layer of cloth electrical tape and finally two layers of vinyl electrical tape. The sticky-side-out layer keeps the self fusing rubber tape from sticking to and gumming up the terminal. The rubber splicing tape seals and provides electrical insulation, the cloth tape provides some abrasion resistance and the final covering of vinyl tape holds the cloth tape in place.

I cut the battery terminal end off the battery cable and crimped on the #4 lug. I then used a 5/16-18 stainless steel bolt, lock washer and nut to fasten the remaining factory end of the battery cable to one end of the fuse block. I cut the protruding threads of the bolt off flush with the nut. I wrapped this connection with same four layers of tape as I used to insulate the 24V feed from the resistor pack.

I fastened the new lug end of this cable to the top post of the glow plug relay and routed the cable along the firewall attaching it to the existing 12V feed. I then bolted the fuse end to the positive terminal of the front battery. I cable tied this new cable to the existing battery cable to provide some strain relief for the fuse. I could have used the negative terminal of the back battery but I already have my 12V radio feed connected at that location.

Now to the glow plugs. I removed the burned out Wellman 070s. About half were swollen and I needed slip joint pliers to get enough grip to gently work them out. None broke during the extraction process. I installed the new AC Delco 60Gs using some copper based high temperature anti-seize compound (from O’ Reilly’s). Next I cut off the old terminals from the glow plug wires. I installed new 0.250 x 0.032 female disconnect terminals (Panduit DNF18-250-C) using an electrical anti-oxidant compound on the wires. I covered the terminals with shrink tubing after installation. I coated the glow plug spades with dielectric grease before connecting the wires.

I then connected the battery terminals and started the truck for the first time in a month. Yeah! Now to test out the glow plug controller.

 

[Warthog]

Great looking installation !!!

You will never overload that cable.

Alot of people will use a smaller wire and tap the power off of the 12v terminal right next to the glowplug relay.

 

[mistaken1]

Today I tested the GP controller as per the TM. My voltages were low until I changed my ground location for the meter and then they looked better. The controller appears to be working, the glow plugs cycled on and off.

It was maybe 28 degrees when I tried to start the truck. Lots of cranking and it finally fired up. I immediately started to back off the throttle and the engine sounded like it was going to quit so I gave it full throttle but it seemed to starve out. Some more cranking and no joy.

Looked under the truck and no leaks or spots on the drive. Crawled under the truck and so no leaks or wet spots until I got to the oil pan. Dirty looking oil that felt thin and smelled like diesel. Crawled on top of the engine and looked around, the fuel filter and base are dry but there is fuel in the valley under the intake. Could not find a specific leaking point but it looks like it is time to replace the rubber fuels lines leading to and from the filter.

So I took a rag and an air hose and put a little pressure in the tank and went back to cranking the starter. It did not take long for the engine to fire up and run fine after that.

Right now I suspect that somewhere between the filter and the IP I am trading a little fuel for air. Just enough to make it hard to start after setting for several days. I don't see any way to replace those rubber lines without removing the intake manifold.

 

[mistaken1]

After more reading here it could be shaft seals in the IP leaking fuel into the valley as well.

Start with the fuel lines and see what happens.

How hard is it to replace the shaft seals in the IP assuming everything else in the pump is okay?

 

[Barrman]

The pump really needs to be pulled to change out those shaft seals.

Think of it this way. If those seals are leaking from being 25 years old, how are the plastic pieces inside the pump doing? Might as well just pull it once, get the IP redone or replaced and then go back to not giving the engine a second thought.

Oh, if you have a 1/4" socket set with a long flexible extension. You can snake your way onto the fuel line clamp under the intake to get it loose. Going back on is funner.

 

[mistaken1]

I checked the IP return check valve yesterday. No crud inside of it, the glass ball is intact and moved freely so I would like to think the IP is not in the process of disintegrating.

After setting just under 24 hours and at approximately 28 degrees it fired right up so I am thinking that it is losing prime after a week or two of setting around doing nothing but looking good.

 

[mistaken1]

These are the glow plugs that failed during the second use. They can be purchased through a dealer on ebay or that same dealers web page.