I have a 93 chevy dually with 6.5L turbo diesel. The glow plug light will come on if the truck is dead cold (haven't been running for atleast 7 hours). If the engine is warm at all though i will not get the glow plug light at all. All it does is sit there and turn over and doesnt come close to firing. I have replaced the glow plug moduel relay thing, didnt do any good... when i try to read the code with my snap on scanner my scanner says that there is no communitcation. yes i did check the ECM fuse its fine. The truck also has a code 21 It like a high idle circut or somthing.. Could that code have anything to do with it starting? Any suggestions on what to do from here? My dad thinks the trucks temperature sensor is bad but idk i really dont want to take it to the dealer.. plz help if you can..

 

It could be the temp sensor but I had the same problem with a 93 6.5 and never figured it out but what you can do to fix it permanatley is go to your local NAPA STB6301 and about 8 ft of 10 or 12 gauge wire run to each post and install switch in dash problem fixed in less than 1 hour

 

Is STB6301 the same kind of relay that is needed for the glow plugs? I wire in the relay on the positive or negative side? or does it not matter? would i turn the toggle off once the truck is strarted? Also you mean the posts of the glow plug controller thingy right?

 

STB6301 is a push button it works only when depressed take your finger off and the circuit is open and yes the terminals to the GP relay do that and your problems are over

 

ok so after i put all this in. Turn the key to on press the button, the glow plug light will come on like usual, and when it turns off take my hand off the button and start it??

 

Glow plugs draw about 115 amps-no push button switch can handle that,you must add a ford solenoid or a snow plow solenoid to the circuit.


The glow plugs stop getting activated by the thermal switch on the passenger side cylinder head after about 120F so as described above the "glow plug override modification"(google it) will help with warm starts.

Another common problem with no start hot is a worn out IP,try pouring some water over the IP at your next warm start-if improvement you have your answer.
The water cools the housing and makes the plungers tighter in their bores with less fuel bypass/blowby at cranking RPM to activate the injectors.

Also the ECM is only for the trans on a 93.

 

so racer are you saying that i shoulden't use the glow plug mod?

 

Use the glow plug mod but do it properly.
Google "glow plug override modification",you will get a link that describes the proper way to do the mod.

Or buy the kit from leroydiesel.com

 

ok so i found out how what was wrong with my truck after days and days of diagnosing. The glow plug light aparently doesnt need to come on when its warm. it should just be able to start off of the compression. The head gasket is blown and isnt allowing enuf compression for the engine to warm start...

 

Good chance that the IP is worn a little also.