glow plug resistor by-pass mod

[tndox]

New to this site. Alot of great info. Thanks . Have searched for the mod, but not found instructions on how to. Resistor has a constant draw on batterys and could probably cook on it. Havent had this vehicle about a week. Wiring for batterys was trash when we got it. Just trying to eliminate all problems i can. thanks in advance for any help. 1985 m1009

 

[K9Vic]

This should help and welcome to the CUCV club.

http://www.steelsoldiers.com/showthread.php?56682-What-is-it-and-why-did-it-smoke
http://www.steelsoldiers.com/showthread.php?96483-Glow-Plug-Resistor/page2&highlight=resistor

 

[Skinny]

Resistor shouldn't draw on batteries unless the GP Solenoid is the incorrect one which is supposed to be isolated from ground. The other thing is search, it is been beat to death.

 

[tndox]

replaced the glow plug relay with Napa st85

 

[86m1028]

Funny how great "SEARCH" is on this site.

Top_prop did a step by step article on this & I cant find it in search !!!!

 

[tndox]

I searched glow plug resistor by-pass mod and had alot of referance to it but no how to. K9vic got me straight and for that Thanks again.

 

[86m1028]

Here it is post #20
http://www.steelsoldiers.com/showth...y-Pass-Help/page2&highlight=glow+plug+by+pass

I know the relay was your problem but here is the resistor bypass thread.

 

[tankie88]

I had relay chatter.So i changed the relay.Still chatters.I did read low voltage on the front batt was the cause of this.I've rebuilt the drivers side alt.Both batts are putting well over 14v.But still chatters.Anyone any ideas???

 

[Ken_86gt]

Sounds like low voltage or a bad ground on the circuit that activates the relay. What is the voltage on relay when it is chattering?

 

[tankie88]

Right,when no ign......25.13v
ign on.............12.28v (on top post from resistor as above)
Small bottom post....13.47 (when running) pink wire
When it starts chattering the volt meter can't keep up with the rapid change in volts.
Oh,and i have swapped batt positions

 

[Vhyle]

I just did the bypass yesterday.

I went to start it this morning in this 19-degree weather, and the glow plugs took longer to heat up (which from what I've researched, is normal). The truck would just turn over and over... didn't fire. I cycled the plugs several times, still nothing. Just turning over and over.

I know I have at least one bag GP on the pass side, as it blows smoke and skips for a few seconds on a cold start (before I did the bypass). I haven't checked them officially. I do know that the glow plugs are old as balls, and so is the GP relay.

Before the mod, the truck starts every time. It takes a little effort in the mornings, but it started every time.

So I'm thinking my diagnosis is 1) old/bad glow plugs, 2) old relay, and 3) glow plugs could benefit from a manual switch. Any thoughts? Or did I miss something else?

Here's my mod. I'm probably going to undo it and go back to using the resistor, so I can still drive the thing. I intend on replacing the glow plugs anyway. And when I re-do the mod, I'll use the fusible link from the other end of the resistor.

 

[Ken_86gt]

You need to verify that the glow plugs are good before you do anything else.If you have a bad plug using the original configuration with the resister you are over power the remaining plugs- this may be why you said it started easier before. But, this condition will cause the remaining plugs to fail very prematurely. You may have multiple bad plugs at this point. With one bad plug you still should be able to start it, it will be hard and smoke a bit...

If the plugs are good did you try cycling the plugs twice and holding the pedal 1/2 way when starting?

 

[Vhyle]

You need to verify that the glow plugs are good before you do anything else.If you have a bad plug using the original configuration with the resister you are over power the remaining plugs- this may be why you said it started easier before. But, this condition will cause the remaining plugs to fail very prematurely. You may have multiple bad plugs at this point. With one bad plug you still should be able to start it, it will be hard and smoke a bit...

I know, that's why I went ahead and did the mod, to preserve the remaining good plugs. But now that the system isn't getting the over-voltage it was likely getting before, it's not firing. At least that's my prognosis.

If the plugs are good did you try cycling the plugs twice and holding the pedal 1/2 way when starting?

Yes. I do that every morning.

 

[doghead]

Why not take 10 minutes and test your GPs?

Why not spend 10 more just changing them?

Why not spend 20 minutes diagnosing the whole system?

It should not "take any effort" to start if all is right(12 or 24V supplied). These things start in about 3 seconds of cranking when all is right(down to 0F)

 

[Skinny]

I wouldn't spend time doing any of that. I would immediately go straight to new plugs, bypass mod, and then a functional check. I'm not sure why anyone would bother trying to use the GP's with questionable history when they more than likely are junk to begin with.

I have yet to buy a car from someone that has the same maintenance rigor as I do...

This along with alternator reuilds, fresh batteries, new rubbers, etc. should be done as soon as your CUCV gets delivered off the trailer.

 

[Ken_86gt]

If I was rolling in Money I would recommend that you also just go ahead and replace the injector pump while you are at it. Sadly most of us are not rolling in money. It only takes 5 minutes to test the plugs.

 

[Skinny]

You don't have to be rolling in money...it is a cost avoidance. Unless you own a tow truck or trailer, it will leave you stranded and instead of doing maintenance you are giving your money to AAA or some other tow service.

Just for the record, I had to do my IP also due to fuel leaks. Wanna play you gotta pay!

 

[Vhyle]

Why not take 10 minutes and test your GPs?

Because I'm certain they are old and junk already. No point, when I am already planning on changing them.

Why not spend 10 more just changing them?

Waiting on payday.

Why not spend 20 minutes diagnosing the whole system?

Already have.

It should not "take any effort" to start if all is right(12 or 24V supplied). These things start in about 3 seconds of cranking when all is right(down to 0F)

I am aware. As I said, my glow plugs look pretty aged, and are most likely garbage. I can really test them but what's the point? If I had tons of cash, I'd do everything at once, but unfortunately I can't. I'm pretty rigorous on maintenance as well. I just have to play "catch up" to get the truck up to full functioning status. After that, rigorous maintenance takes place.

Injector pump... yeah, that will be a future endeavor. I have to make do in the meantime.

 

[doghead]

One point of testing them is, then you will know which cylinders have bad GPs. Later on, when you have issues, you may recall(I make notes in a book) that a specific cylinder had the tip burned off, and that is a good indication you have a bad injector.

Information is always useful.

You'll get no info if you simply replace everything.

You can do whatever you want to, with your truck.

Just please don't litter our forums with bad advice.

 

[cpf240]

If you have a meter, measure the output side of the GP relay when it is energized. I've seen several here on this site, as well as my own vehicle, where the contacts in the GP relay had carbon build-up preventing a good connection. For me, this did not show up until I did the bypass. I'm guessing the lower available amperage of the bypass could not overcome this. I replaced the GP relay, and all is well.

If this is the case, in a pinch you could take a heavy-gauge piece of wire and jumper the feed to the glow plugs for 5 or 10 seconds and then see if it will start.