need Glow Plug Relay help

[cfish]

Ok so I have been looking thru the TMs and pictures here of the GPR change out. Mine has the newer style GPR like the one in the CUCV facts picture. As i was looking under the hood yesterday, I noticed something strange. The two red leads with white markings coming from the sheilded area on the fire wall directly behind the airintake are cut. The one on the drivers side should have been going to my GPR, not sure where the other one went. Looks like someone made a jumper cable and attached the GPR directly to the 12v bus next to it. Isn't that sheilded area the the dissipator? Can someone explain what the previous owner did?

 

[cfish]

Sorry I meant voltage dropping resisitors not dissipator. Looks like they bipased these and tied right into the 12v bus.

 

[rnd-motorsports]

Yes that itam in question is a resitor the pass side wire out of it should have bee hooked to the top 24 volt junction block on pass side and the driver side wire to the glow plug relay the owner before you just hooked it to the 12 volt factory juntion block no need for the resistor and will still work. is the truck still wired for 24 volt starter or has it been switched to a 12 volt starter?

 

[cfish]

As far as I can tell its still 24volt. What should I look for to determine this?

 

[rnd-motorsports]

Easyest way is to look at battery cables the front battery pos cable if it s conected to the rear batterys ground post then its 24 volt if both batterys are ground to ground then its 12 volt does it still have two alts? only need one if 12 volt the second will be and idler if 12 volt

 

[cfish]

Yep front battery + is connected to rear battery -. It has both alts still. Puzzled by why he bi-passed the voltage dropping resisitors.

 

[doghead]

It is a common modification.

with a stock system, when one GP burns out(and they do), then all the rest of them will burn out. (it's simple math and using the resistor to drop the voltage).

With the GP relay is supplied with 12v, it makes no difference when one or 2 glow plugs burn out.

Personally, I resupply the GP relay with 12v.

 

[ranchhopper]

A lot of time the resistors are bad thats why they were bypassed I take a 8 gauge wire and run it from the + on the front battery to the top post of the glow plug relay.By doing it this way you dont pull both the voltage for the 12 volt system and the GPs off the same battery you split the load useing both batteries.

 

[cfish]

They have it tied to the 12v bus on the firewall next to the GPr. By the way is the GPr part # STG58? I have the new one in mine like in the cucv facts post.

 

[rnd-motorsports]

The resitor may have gone bad If you want to put if back as it was. I think I I have a good one I convert all mine back to 12 volt less parts to go bad and easyer to fix! I will check and pm you if I have one

 

[cfish]

Thanks and I answered my own question. ST85.

 

[Doc Bingo]

Need Help ... M1009

I replaced my solenoid on the fire wall with napa part st 88 a 24v ... I had an original 12v on there .... however after reading thru all the threads I put the 24v on as recommended.... With the 12v I couldnt start my M1009 in the morning with out starting fluid. After that it would start up just fine thru out the day. It was just the initial start up. Now I have the new 24v on there after installing it the truck started up asap even the wait light didnt come on for longer then a second. Went out this morning to start it up and the wait light stayed on twice as long as before and wouldnt start without starting fluid. Any suggestions ....

 

[Disciple]

DON'T use starter fluid in these trucks, unless you like replacing engines. With everything working correctly, there should be no reason to use it in the first place. I regularly start my M1008 on FRIGID Minnesota mornings (I'm talking double-digit negative temps all night) after it's been sitting a week or more, with no outside help (no block heater, no intake heater, nothin'!).

The GP Relay most guys use and recommend here is found at NAPA: Part Number: ST85. I would guess that you're GP's are either shot or not getting juice. I don't know about this other relay you used. Sounds like you fried something. I'd start by getting the ST85 and start tracing circuits. Make sure you're getting power to the GP Relay, if not, check your GP Controller Card. If it's not working, replace or bypass with a switch. Once you've got juice to your plugs, check them. Most guys recommend ACDelco 60G's, especially if you're going with the push-button system (they're self-limiting and less likely to swell than the Wellman's).

There's lots of info on this site about all of this, it just takes time searching and reading. Download and print out the -20 TM (the Unit Maintenance Manual). It can save you a lot of time and headaches. It can be found by clicking "Forum" above, then go to CUCV, then CUCV FAQ at the top, then scroll down to Technical Manuals. I personally saved a lot of this stuff to my iPhone so I can have it all right there when I'm working on my truck.

 

[doghead]

The GP relay is 12V and the coil is NOT grounded by it's mounts.

 

[mistaken1]

A lot of time the resistors are bad thats why they were bypassed I take a 8 gauge wire and run it from the + on the front battery to the top post of the glow plug relay. By doing it this way you dont pull both the voltage for the 12 volt system and the GPs off the same battery you split the load useing both batteries.

I am sorry but I do not understand how the load is split between both batteries. When you have a minute could you please elaborate further? Thanks.

 

[mistaken1]

I replaced my solenoid on the fire wall with napa part st 88 a 24v ... I had an original 12v on there .... however after reading thru all the threads I put the 24v on as recommended.... With the 12v I couldnt start my M1009 in the morning with out starting fluid. After that it would start up just fine thru out the day. It was just the initial start up. Now I have the new 24v on there after installing it the truck started up asap even the wait light didnt come on for longer then a second. Went out this morning to start it up and the wait light stayed on twice as long as before and wouldnt start without starting fluid. Any suggestions ....

Why would you install a 24V coil relay when the system is designed for a 12V isolated coil relay?

It seems to me that 12V would not be enough voltage to properly energize a 24V coil.

 

[ranchhopper]

Why would you install a 24V coil relay when the system is designed for a 12V isolated coil relay?

It seems to me that 12V would not be enough voltage to properly energize a 24V coil.

If your resistor on the firewall was bad it was shooting 24 volts to the GP solenoid by going to a 24 volt solenoid you dont burn out the solenoid but you still fry the 12 volt glow plugs.

 

[Disciple]

I take a 8 gauge wire and run it from the + on the front battery to the top post of the glow plug relay.By doing it this way you dont pull both the voltage for the 12 volt system and the GPs off the same battery you split the load useing both batteries.

Not true. That's the only flaw about doing the Resistor bypass. The Resistor is getting 24V (both batteries) and dropping the load to 12V (still both batteries) when the GP Relay is energized. They designed it this way because the GP's take quite a bit of power to warm them. The RESISTOR allows you to draw off both batteries.

By removing the Resistor (bypassing and feeding the GP Relay directly with 12V off the FRONT battery (12V)) the GP's will only be drawing off the front battery. The plus side of this mod is that you don't have to worry about the Resistor changing impedance and frying all of your GP's at once. It doesn't matter if you hook your new feed wire to the + of the front battery or the - of the back battery, electrically it's the same thing and you are still only getting 12V+ from the FRONT battery.

If you do this mod it's even more important to keep an eye on your Volt Gauge, knowing that you are drawing down your front battery even harder than before when cycling your plugs.

 

[ranchhopper]

I am sorry but I do not understand how the load is split between both batteries. When you have a minute could you please elaborate further? Thanks.

If you use a jumper wire off the 12 volt power source at the firewall by the glow plug solenoid to power the solenoid your not only drawing the power to energize your glow plugs but the 12 volt power feed for the rest of the truck comes from the same source tapping the power from the front battery.If you look at the stock configuration the power for the GPs is drawn off the 24 volt positive bus bar on the firewall going through the resistor feeding 12 volt power to the GP solenoid eliminating the draw from one battery. If you tap the front battery for your power source to fire your GPs your not useing the rear battery for all power needs for the truck.

 

[Disciple]

If your resistor on the firewall was bad it was shooting 24 volts to the GP solenoid by going to a 24 volt solenoid you dont burn out the solenoid but you still fry the 12 volt glow plugs.

Well, at least now I see your point. I think you're getting into shaky ground though. People are going to read this and think they can just use 24V GP's and a 24V GP Relay and remove the resistor bank and feed the whole thing 24V and get away with it, not understanding the rest of the system. I'm guessing this would be a sure-fire way to fry your Controller Card and who knows what else. I'd have to look through the wiring schematic, but I'm guessing there is other stuff tied in with this system, just judging by the number of wires coming out of the GP Controller Card.

Changing to a 24V GP Relay is not a fix. Get the ST85 and possibly new GP's and start from there.