Hey again, I checked all g plugs and all are good. I replaced gp relay and light just flashes once real quick. Yesterday a guy left the ignition on for an hour but it ran after that. I heard the cam sensor could cause it but sounds remotely possible. I am stranded if anyone can shed light i'd appreciate it

 

More than likely the controller. There is no cam sensor on an IDI.

Glow Plugs 101 Tutorial

 

Is that what I am calling the relay. I replaced what is behind the air filter and when I took the old one out the two bracket screws fell down into the black base and I left it only being supported with the metal wavey piece that is secured on one of the big posts (positive ??). Do those screws act as a ground ?

 

Both are back there. The relay is the brown or black cylindrical piece with the 4 posts on it, similar to a starter relay. The controller is the black box it sits on, with several wires coming out of it.

Def. read the whole post on GPs that Chevy_eater posted. Evey question on GPs has pretty well been asked already. Here's a little extra info anyways if it helps.

Here's a picture of the controller and relay. You don't mention the year of your truck; I hear that the earlier engines had a different controller, just confirm that yours looks like this one. (note this one has some of the wires disconnected)


First, yes, bolt the relay back onto the controller, and ensure that the black wire from the controller is connected to a good ground. (You can see the ground wire just south of the controller in the pic above)

Then make sure that the controller is wired correctly. Refer to this:
(note that some of the colors are different for different year trucks; this is for 1994. Should be able to figure it out anyway)


If everything is good, check the fusible links. These are essentially combustible wires that act like fuses; there are two coming off the controller going to the GP harness (off the bottom of the wavy metal thing, one for each bank of 4 GPs) and replace if necessary.
This is what a failed one looks like:


Checking all the bullet connectors that push on to the GPs would be a good idea as well, as they are known to be a bit sketchy.

The wavey metal piece is a resistor, and it heats up, so don't hang anything off it or allow it to short.

Good luck!

 

Yours is an '87 or newer correct? On the new system (87+) the relay bolts to the top of the controller. Sounds like you replaced the relay and left the old controller in.

And yes, I'm pretty sure the relay grounds through the mounting bolts.

 

Ooops, ND beat me too it, sorry for the redundant post.

 

Thanks for all info I have the controler ordered and will be delivered to my breakdown position (Walmart). Slept in the truck last night and woke up ready to pull the trailer the rest of the way to get paid but no start. I have put 70,000 on this baby in 6 months and only regular maintenance , two flats and alternator, I love this machine. Thanks again

 

Not sure if anyone will see this. My problem is still there after all that. All the wires are intact and hooked up correctly and it will start but only with a shot of either and the light still just blinked real quick. After it sits at night and is cold it won't start but after its been running throughout the day it starts quick and everytime.

 

Double check your glow plugs. By design the new system won't cycle properly if two or more plugs are bad.

Also remember that a manual GP switch is an option too if you can't get the bugs worked out.

And be sure if you must use ether to disconnect the GP system first to reduce the chances of destroying your engine.

 

use a jumper wire to jumper the relay, from the hot supply side to the small post that trips the relay if no click check for bad conection at long post of start relay,,(it is used for a binding post for all loads)the power for the GPs comes from this point..check for bad fuseable link..you may find a test light usefull at this point...sounds like bad conection, loss of power to gp relay...diferant power sourse than controller..