Glow Plug Module Problem

[rmesgt]

Hello All... I have been working on trying to fix the Glow Plug system in my M1009. Thanks to the sticky notes and other information in the helpful threads, I think I was able to isolate what I believe is the primary problem. Coming from the GP Module Housing, I noticed that the wires split into two paths. One path goes out into the engine compartment while the other path goes into a 6 pin connection. Within this 6 pin connection only 4 1/2 of the pins are used. I say 4 1/2 because on one side of connector there are 5 wired pins (one of which is Blue w/ Red Chaser that goes into the engine compartment and stops). On the other side of the 6 pin connector there are four wired connectors (there is no mating connection for the Blue w/ Red Chaser wire). These wires quickly disappear into the wiring harness. I chose to call this side of the 6 pin connector "Truck Side".

The four wires on the "Truck Side" of the connector are: Black, Pink w/ Black Chaser, Dark Blue and Purple w/ White Chaser.

Black goes to Ground - Verified with my meter set to continuity.
Dark Blue goes to Glow Plug Wait Light - Verified with my meter set to continuity.
Purple w/ White Chaser goes to Ignition Switch (Not Verified - Information gained from image provided in Sticky Notes)
Pink w/ Black Chaser goes to two places. Place #1 = Glow Plug Wait Light, Place #2 = 12V FUSED Power source when the key is in the RUN position (as depicted on the schematic).

In my case, I do not have power to the pink w/ black chaser wire when the key is turned to the RUN position. According to the schematic, this wire gets it power from a fuse. I determined that this wire (and perhaps the fuse) is only energized when the key is in the RUN position by using my test light on my FMC M1008.

How do I determine which fuse is supposed to be the power source for the Glow Plug Module? As best that I can tell, every fuse in my block is a good fuse. I tested each one with my meter set on continuity.

If all of the fuses are "Good", then the problem could be between the fuse block and "Truck Side" of the six pin connector and/or the wait light, however, it could also be a disconnect between the ignition switch and the fuse block which would prevent the fuse (whichever one) from being energized when the key is turned to the RUN position.

Thoughts anyone???

 

[cucvmule]

Have you separated the the fuse box yet? Look to see if the connections in the box are clean of the water protection paste.

I took mine and separated the box and cleaned the contact points up, enough to make the contacts work and put mine back together and cured allot of my wire problems.

 

[cucvmule]

CUCV Diagnostic plug under dash, is that the wire you are talking about?

 

[rmesgt]

CUCV Diagnostic plug under dash, is that the wire you are talking about?

The six pin connector is not the diagnostic plug. This little guy hides under the steering wheel up next to the fire wall.

 

[rmesgt]

Have you separated the the fuse box yet? Look to see if the connections in the box are clean of the water protection paste.

I took mine and separated the box and cleaned the contact points up, enough to make the contacts work and put mine back together and cured allot of my wire problems.

 

[rmesgt]

I am happy to report that I found the hiccup in my Glow Plug System. The problem was in the 10 amp fuse. Using my meter in continuity mode, I tested the fuse between the test points (see the picture) and it tested "Good". At this point, I assumed the fuse was good. I began looking for the problem elsewhere, but I kept returning to the fuse box. Finally, I yanked out every fuse, thinking that if I put them back in one at a time, the problem may self-correct. What I realized was that even though the fuses tested "OK" between the test points, the fuse spades were so corroded that the energy was not getting across the fuse and into the wires. Once I cleaned the fuse spades, everything began to light up and work.

With most things working OK, I took a chance and started the truck. It fired up within two seconds. Needless to say, I was shocked that I fixed my glow plug problem. I backed the truck out of my garage and cleaned the floor. Finally, I pulled it back into the shop and shut it down.

 

[rmesgt]

I have not yet tried to separate the fuse block from the connection block. I am somewhat hesitant to try this. I do have access to a donor car (89 Suburban). I will practice on it before I chance the same procedure with my M1009

 

[Barrman]

Verify the ‘89 has the same type of fuse panel before you play. I have an ‘87, ‘88 and a ‘90. The ‘90 has a way different fuse panel than the others. They come apart the same, but if you are going to practice at least practice with similar parts.