Cucv goes to WOT on startup

I recently purchased another project m1009, I put a new starter relay in it and it started right up, but always needed the block heater for it to start. It sounded like the glow plug controller was bad because the relay was just clicking on and immediately back off so I wired u button into the light blue wire and the relay cycled properly with the button, but it still would not start without the block heater. I put in a new set of 60g glow plugs and now the controller turned the plugs on, but I did not hear it click off even after the light went out. I went ahead and tried to start it anyways and it immediately fired up, but went to full throttle. I turned off the key and it cut off and I have not tried to start it since. It only sat 1 day between when I last drove it and then trying to start it with the glow plugs and all that was changed was the glow plugs and vacuum regulator, but I don’t think either would cause the issue. Could it be because the relay is keeping the glow plugs on? If it makes a difference the truck does have a decent amount of blowby, with the cap on you can still see the steam coming out. It did run and drive great before replacing the glow plugs except on cold starts. Sorry for the long post, but I want to make sure I give the whole story so it might help figuring out the issue.

Sounds like the GP system is working properly. The glow plugs will stay on for up to 45 seconds after the wait light goes out. This "after glow" time depends on how cold the engine temperature sensor is.
The GP system will keep the plugs supplied with power for a short period of time even after the wait light goes out.

The GP system and the throttle system are two different systems. I would look and see if new vacuum regulator has caused the IP to go to full throttle.

Ok, thanks. I was a little concerned about the glow plugs because on my other cucvs it clicks off before the light goes out. I was unaware that the regulator could cause that, but I will check that. I’m always learning new things about these trucks from this site

I checked the regulator and it was not holding the throttle so i figured I would disconnect the high idle solenoid and it started and idled normally, so I guess that was somehow causing the issue or the issue fixed itself somehow. Since it was running right I waited to see if the glow plug relay went off after a while and it didn’t so I just wired up the button to completely bypass the controller and all is good now. Now I just have to do some body work and track down why the turn signals and hazard lights do not work on the passenger side

Idle speed is set by spring tension, the metering valve is nearly wide open when the engine is off. If there is the slightest varnish in the injection pump, this WOT can happen. Often, the metering valve will then slam shut from the governor overshoot, if there is varnish there, this will kill the engine.
Pull the IP cover, remove as much diesel as possible and replace with Diesel Mechanic in a Bottle. Reinstall the IP cover , carefully noting the shut off solenoid lever!!!! Let the IP clean itself over four hours. Varnish will be softened, allowing the engine to run. Continue with 1 ounce per 5 gallons of diesel until it runs right. Its magic in a bottle.

Maybe check linkage and position of high idle solenoid, may just be out of adjustment, or mounting bent or such.

Ok, Thanks guys. It seems like it was just a coincidence that it didn’t go wide open after I unplugged the high idle solenoid because it has still done it a couple times. It only does it if I have not held the glow plug button long enough and have to crank it for a while, then if I pump the throttle a ton and restart it, it will idle fine. If I hold the button for around 20 seconds the first try when it is cold it will start right up and idle fine. I will try to clean it out with that diesel mechanic in a bottle. I always run stanadyne in the fuel, but I guess that isn’t in high enough concentration to really clean out heavy stuff

Diesel MiB is a different solvent than others. Smells like concentrated 409 so its probably a glycol ether which would explain its cleaning power. It will remove oils from your skin and rinse with water. Also dissolves engine oil varnish.