I've been trying to correct the problem of my glow plugs continuing to operate for about 20 seconds after the engine is started even when the engine is at operating temp. I changed the oil temp sending unit today (thank you Itfox for the part number! ) and the problem actually got a little worse. The glow plugs stay on for about 29 seconds now. Any ideas?

 

I didn't think this was a problem my truck does this when it's cold out even if the truck is up to normal operating temperature. May be it just take this long for the computer to shut em down?

 

I suppose you could be right but there is really no need for the glow plugs to operate when the engine temp is up (or outside temp for that matter). The thing I'm after is to prolong the life of the of the glow plugs. My understanding is that the computer gets input from the oil temp sensor and also considers atmospheric pressure (don't know how it gets that data).

 

Guys, this is a good point I have seen before as well. I seem to remember reading here, guys putting a switch to kill the GPR all together once they crank her for the first time and get the PSD to operating temps. Then when they park the PSD and its allowed to cool all the way down, flip the switch back on allow the relay to cycle the GP's.

Would be easy enough to do with putting a switch inline on the trigger wire of the GPR and running the wires into the cab with the switch. Might be something you would be interested in.

 

You can get a temperature switch from napa, it is used to turn on a fan for vehicle with electric fans, I had the part number but lost it and then install it in the thermostate housing right by the engine temp sensor, cut the wires from the PCM the GP solinoid, run them down to the new Temp switch and as long as the engine is warm the GP will never turn on, but once it cools down to the set temp of, I think 170* they will work normal. since you only splicing into the control wiring and not the actual GP wires it is real easy quick and cheap. and work nice.


Diesel Rod

 

I guess I'm gonna have to start looking at doing something like a switch or maybe the fan switch idea. Thanks for the ideas guys!

 

fastfreddie-
I'm willing to bet that you've got a '95 truck with an automatic, and that you're computer box code is TEE5. The glow plugs cycling whether the truck is warm or cold is a function of the pcm programming. What you're describing is exactly how my truck acted before I got my first chip. Later programs, like the TDE0 or TDE1 only cycle the plugs when they're needed. Imagine that!!

 

Quad that would be AWESOME. how and where do you learn about these box codes. I hear all about them but have never heard of anywhere I can read about them. and While we are on the subject of box codes. Where is the computer in these things (OBS) just to clarify I have not done any looking yet to find it will be doin a swap tomorrow. must find!!!

sorry for the hyjack, back to the GP's do the fan switch. I lied a lil earlier and fergot about the relay!!!!! since the switch is a normaly OPEN, you will need a Normaly closed relay, once the switch is hot, it closes, thus opening the contacts on the relay and disabaling your GP's.


Diesel Rod

 

I've got over 2300 posts on this forum, well over 3000 on another one, plus about 500 on various other ones. I obviously spend a lot of time on forums, and most of it is reading and learning. What I know about box codes I learned doing the research on my own issues: glow plugs cycling regardless of how warm the truck is, poorly spaced shift points, lousy torque convertor lockup characteristics, etc. I merely asked a lot of questions, and paid attention to the answers.
Your pcm is located behind the emergency brake pedal, in the bulkhead. You can see it if you remove the plastic kick panel surrounding the emergency brake, then pull the three 13mm bolts that hold the emergency brake in place. After pulling the emergency brake off, you'll see the pcm in the recessed hole. You won't be able to remove it that way, but you'd at least be able to get a look at the black plastic cover on the end of the pcm, which would tell you what your box code is, unless someone has already removed it.
To remove the pcm, you have to go in through the driver's front fender. You can disconnect the wiring harness inside the hood. It's attached to the pcm at the firewall. Then, after pulling back the inner fender lining, you'll be able to work the pcm out through the fender.
I hope this helps.

 

OK, I know I'm dense, so here's my question...
Which wire would I put the switch on to turn the glow plugs off ??
There are a lot of wires under the hood and I want to make sure I get the right one.
Thanks.

 

Thanks Quad. Have to do some more investigating on that. and I like the Avatar, seen it awhile ago just haven't said anything about it.

right above the passenger valve cover towards the front is a thing that looks like a solenoid, which it realy is. it has two big wires and two smaller ones. if you tap into one of the smaller one with the relay it will work. One is the power, one is the ground, it doesnt matter which one. I can try to find a wiring diagram somewhere if anyone wants it.


Diesel Rod

 

Thanks, so it doesn't make any difference which one I put the switch on ??

 

Here is the wiring diagram http://www.dzljim.com/images/F-350_p...GPRdiagram.JPG. I didnt install the switch, just the relay and the temp switch. it's a lil complicated but to answer your question. no it doesnt matter which wire you put the N/C relay in, as long as it is the small wires. they are the ones that "control" the GP relay. The big wires are for you GP's and they will FRY a small napa relay.


Diesel Rod