Resistor Bypass Questions

[KWA]

Aloha everyone,

I recently bought a 1986 m1008. It was an impulse buy, 1st diesel I have owned. Well after doing some research here I can see there are a lot of problems that need to be fixed.

It starts with starting fluid, nothing else. I know now thats a NO NO, but again my first diesel

Needs a Glow Plug relay (got to get the Napa st-85)
Needs Glow Plugs (got the AC60G)
Needs starter relay. PO put in a push start (doghead mod.)


So the plan is to follow American Haoles plan .
http://www.steelsoldiers.com/cucv/83103-glow-plug-process-overhaul.html

I will start with phase 4:

So the Resistor Bypass Question. There seems to be 3 ways to do this.

1. Cut the cable coming out of the resistor and attach it to the 12V bus.
http://www.steelsoldiers.com/cucv/80047-smoke-after-glowplug-swap-2.html#post1016300
2. Connect a cable from the 24V bus to the GPR


3. Connect cable from positive front battery to the GPR
http://www.steelsoldiers.com/cucv/56682-what-why-did-smoke-2.html

#3 seems the easiest and cleans up the engine bay.

Am I missing something or would this route be okay?

 

[DriverSideImpact1008]

NO on #2 (unless you buy 24v GP's). You will fry the GP's quickly. That resistor is there to drop the voltage down to 12v.

I cut the wire from the resistor, and put a new ring terminal on it, connected that wire to the 12v bus, and then removed the entire resistor and the wire going to it. There's already a 12v wire running to the 12v bus an inch to the left of the GP relay...and it already has a fusible link in it for added protection.
I felt it was much cheaper, easier, and looks cleaner than running another 4 feet of wire from the battery to the GP relay ($0.90 vs $10).

 

[KWA]

Okay, I understand it better now.

I misunderstood my #1 and you just made it clearer. You basically did what it was suggested in #1

I'll go that route.

Mahalo

 

[doghead]

#1 is easiest.

Needs starter relay. PO put in a push start (doghead mod.)

The "doghead mod" is not a push button start.

 

[DriverSideImpact1008]

^^ Then again...that guy doesn't know anything about the doghead mod

Are you trying to return the ignition system to stock, or just putting in a new starter relay?
The doghead relay is a great mod to do. But you should check out the TM's for wiring diagrams, trace the wires on your truck, and try to figure out how the P.O. wired that push button in.


Glad I could help clear up the resistor questions.

 

[KWA]

Trying to put the ignition back to stock.

PO I'm guessing had a push button start to bypass the relay. The push button has one wire going to the starter and one going to the top of the GPR (for 24volts )

The ignition switch works but I only get a click. I do need to read up a little in the manual, but that was my initial guess

Mahalo again

 

[CycleJay]

Hi guys,

My apologies, I do not mean to hijack someones thread but, I do have a question...

What is the point of bypassing the glowplug resistor in the first place?

 

[cpf240]

Hi guys,

My apologies, I do not mean to hijack someones thread but, I do have a question...

What is the point of bypassing the glowplug resistor in the first place?

In the stock configuration, with 24v being supplied to the GP relay via the resistor, there is the risk of a cascade failure of the GPs due to over-voltage conditions if one or more GPs fail.

Re-supplying the GP relay with 12v eliminates this potential failure.

 

[CycleJay]

Hello CPF,

Thank you for answering my question. I got it now.
Hmmm, perhaps I should do that with my M1009 too.

Are there any disadvantages to doing this mod?

 

[cpf240]

The only disadvantage that is commonly mentioned is that the GP system will not get the benefit of a 24v slave cable jump start from another NATO slave cable equipped vehicle. The 12v bypass for the GP system was the very fist mod I did to my truck, followed by the DH starter relay mod.

 

[DriverSideImpact1008]

Trying to put the ignition back to stock.

PO I'm guessing had a push button start to bypass the relay. The push button has one wire going to the starter and one going to the top of the GPR (for 24volts )

The ignition switch works but I only get a click. I do need to read up a little in the manual, but that was my initial guess

Mahalo again

So he used the 24 volt feed from the glow plug relay with a push button to crank the starter?

Well you have fallen victim to the very common, "P.O. rewiring muck-ups."

Hopefully he left all the stock wires intact, so you can just re-hook everything up.

 

[seabee mike]

NO on #2 (unless you buy 24v GP's). You will fry the GP's quickly. That resistor is there to drop the voltage down to 12v.

I cut the wire from the resistor, and put a new ring terminal on it, connected that wire to the 12v bus, and then removed the entire resistor and the wire going to it. There's already a 12v wire running to the 12v bus an inch to the left of the GP relay...and it already has a fusible link in it for added protection.
I felt it was much cheaper, easier, and looks cleaner than running another 4 feet of wire from the battery to the GP relay ($0.90 vs $10).

I have done this . First the cut and move then directly to the battery. My truck would not start. I hooked the wire back up to the resistor and it starts. What gives? I have made sure i did it the correct way. the wire had 12v going to it but no power to the GP.

 

[DriverSideImpact1008]

^^ What GP's are you using? Does your wait light come on? Is your GP controller card possibly bad?

 

[mistaken1]

I have done this . First the cut and move then directly to the battery. My truck would not start. I hooked the wire back up to the resistor and it starts. What gives? I have made sure i did it the correct way. the wire had 12v going to it but no power to the GP.

If you had 12V on the wire but no power to the GP (the plugs themselves I assume) then there is an issue with the relay.

Either the relay is bad and not passing power from the wire (input to the relay I assume) or the controller is bad not energizing the relay.

Time to get the TMs and troubleshoot the glow plug system.

 

[seabee mike]

I have new ac 60g plugs.
The light did come on but it did not cycle like normal.

How can it work one way Stock, and not the other?
The way i tested the power to the plugs was using a light and turned on the power. grounding out on the engine.

If the card is bad what happens or not happens?

 

[cpf240]

Can you hear the GP relay cycling? Is the GP relay the original one? Perhaps the internal contacts of the GP relay are carboned up, and the 12v supply is not enough to cut through it, where 24v will.

After doing the 12v bypass on mine, the GP relay would occasionally fail to pass the 12v to the GPs. New GP relay, problem solved.

 

[seabee mike]

I did not now that you asked. I just saw the light come on and go off.
sounds like we know the problem.

Thank you. What part number is the item? Ya i know it is listed here some where. LOL

 

[southdave]

ST85 from Napa for 50 bucks

 

[seabee mike]

Thank you very much.