How long for glow plugs to work?

[Shrapnel]

When I went to fire up my M1010 this morning it was around 70°F and the truck had been parked in the shade. I turned on the ignition and waited for the WAIT light to shut off. It seemed to take forever. I finally got tired of waiting and cranked the engine. Took me three times to get it to start.

My main question is how long do the glow plugs normally take to work in this temperature range? I've only had the truck a week, but every other time it only took a few seconds for the WAIT light to shut off and the truck would start right up. It has been very hot here in upstate SC lately and this morning was one of the cooler ones after some evening thunderstorms.

This M1010 was converted to 12V. I checked the GP relay to make sure it was actually getting supplied with 12V. It read 12.68V on my voltmeter at the top post of the relay. The bottom didn't read anything, but the engine was already hot then so I doubt the GP's were doing anything.

 

[smoke]

I believe at that temp probably 30 second to 1 minute before cranking.In cold weather more time needed. Also in cold weather they may cycle after started and running I would check gp relay again after engine cooled down again make sure volt going though it both circuits. Before starting ignition on not running. if power going though than could be glow plugs going bad. There is a test for them. You can ohm them out check resistance. I cannot remember spec thou. Maybe someone else will chime in with spec.

 

[Hasdrubal]

" probably 30 second to 1 minute" What? are you just randomly throwing numbers out there or do you live in the Arctic? At that temp, with AC60's the light goes out at 7 seconds and I burn for another 7 for a total of 14 seconds.

 

[smoke]

sorry going off my buddy's 84 1 ton (civilian) he had. My bad.

 

[HoJoPo]

It usually takes 30 seconds to a minute (in colder temps) for my glow plug light to go out on my M1010, with the stock glow plugs at 24V. Well, I assume they're stock, the previous owners didn't change them, though the military might have....

When my batteries were miswired and I only had 12V, the glow plug light did not go out even after a couple minutes, until I started it up and it warmed up.

Sounds to me like you have 24V glow plugs and they don't get hot enough on 12V, or you have a bad temperature sensor.

 

[3dAngus]

Not familiar with the electronics in the M1010, but I honestly don't know why glow plugs would be needed at all in these kinds of temps in any kind of diesel.

 

[Shrapnel]

I was under the impression that all CUCV glow plugs were 12V. There is a resistor in the wiring to step it down from 24V to 12V. Mine doesn't have a resistor on the feed line, which is OK for me since I have a 12V system.

I'll have to search and figure out the ohm checking to see if my plugs are good. Also, if I want to change them out to the AC60's do I need to do anything to the harness?

 

[Barrman]

The glow plugs in a 6.2 should come on anytime the engine is below 125°. It is an in direct injection engine and needs the help to get started.

We are around 99° today and I have started 3 different 6.2 trucks in the last little bit.

Civilian 6.2 in an Air Force Suburban took about 15 seconds and then after glowed another 10-15 seconds.

M1009 with a CUCVElectric card in it glowed for about 5 seconds and not again.

M1010 with all stock everything glowed for maybe 5 seconds and nothing else.

Since the civilian and military glow plug systems are totally different. I would not compare them to each other for diagnostic purposes.

Good plugs in the military system should glow less than 10 seconds in temps above around 60°. We are close to 100° today and I didn't get my seat belt latched on the 1009 after turning the key on before the light went out.

I would suggest Ohm checking your glow plugs because you probably have a few that aren't working at this time.

 

[Barrman]

I got distracted from the time I started writting above until I posted. Didn't see your post until later. Sorry.

The 60 plugs have a different size spade on them. You can cut the corners off and keep the wiring stock or cut the plugs off the wires and put bigger plugs on. One of those 6/half dozen things.

All the CUCV glow plugs are 12 volts.

 

[BKubu]

The FIRST thing to do with ANY CUCV is to change the glow plugs whether they are working or not. Go with non-swelling glow plugs. You will thank me later. A swollen glow plug is either a PITA or a royal PITA...either way it is no fun. Swap them out.

 

[Shrapnel]

I checked my GP's this morning when the truck was cold. While the GP's were cycling I read 10.6 V at the top and bottom of the GP relay. I'm assuming the GP's dump a pretty good load on the batteries and that's why I didn't get the 12.7 V I do when nothing is on. The glow plugs cycled a lot quicker than yesterday, about 15-20 seconds and then she fired right up.

I'm going to go ahead and replace the glow plugs. I read the TM section on it and have a few questions. Should I change the plugs with the engine warm or cold and should I use antiseize when putting the new plugs in. I've always done spark plugs when the engine was warm/hot to help seized plugs come out in one piece and not strip threads.

I'm currently on the steep learning curve of diesel mechanics...

 

[mistaken1]

I change my glow plugs when the engine is cold as I reach the back plugs from underneath (arms on exhaust pipes). Anti-seize is a good thing.