m1028 starting issue

[FLINT]

Hi all,

Just recently my CUCV has not been starting as reliably as usual. I've noticed that sometimes the glow plug light will stay on an extra long time. When this happens the truck absolutely will not start, it will just crank and crank and smoke will pour out the exhaust. So, my strategy, is that I'll turn the key off, wait a minute, and then on again, and if it seems like the glow plug light is staying on too long, I turn off, wait, and turn on and repeat until the glow plug light only stays on for a regular amount of time, and then the truck will start right up.

it doesn't seem to be a progressive thing either. so, sometimes, the glow plug light stays on for the 'right' amount of time the first time and it will start right up. it seems like there is something happening - or not happening electronically - that is having an effect on starting.

Does anyone have any experience with this?

Thanks!

 

[doghead]

We've covered this hundreds of times. Have you searched and read the forums?

I would follow the step by step instructions in the -20TM, in the troubleshooting section.

Your problem is 100% documented there.

 

[FLINT]

Ok, thanks, sorry, I wasn't sure what the problem was, so I didn't know what to search for. I'll check out the TM

 

[FLINT]

Right after I posted this earlier this summer, the problem seemed to go away - so I kind of forgot about it - figured it fixed itself. Anyways, the problem is back, except now, no matter how many times I turn the key to on - the glow plug light now will never stay on the correct amount of time, and the truck will never start.

So, I did a search on this forum, and read the -20TM as instructed, and its sounds like my problem might be the glow plug relay?????

When the light final does go off, I turn the key and white smoke comes out of the exhaust, but the engine never attempts to start, and then usually the glow plug light comes back on by the time i'm about ready to quit cranking.

I don't have an electrical tester (yet), so I haven't done any voltage testing at different points - but does the glow plug relay sound like I'm on the right track at least?

Thanks

 

[cpf240]

It could be a number of things. Perhaps the relay, or the temp sender, or the card, bad glow plugs, etc. A volt meter and the troubleshooting steps in the TM should pin point the problem. You could try jumpering the two big lugs on the glow plug relay for 5 seconds or so, and then try to start it. If that works, it does not mean that the relay is bad though, just tells you that at least some of your glow plugs are working.

Get a DVM, test it out, and let us know!

 

[Westech]

Fast cycle times means bad glow plug(s). If one or more fail and you still have the 24-12volt resistor on the fire wall hooked up the voltage will be higher and higher as the plugs take a dump. The card will see this high voltage and try to save the other glow plugs by only energizing them for a brief amount of time. Remove the glow plugs and see how they look. If the tips are cracked, split or swollen time to replace them. In a 6.2 your doing good to get a year or two of service out of a set from what I have seen.

 

[Recovry4x4]

I'd wager on the GP relay being bad.

 

[MakersTeleMark]

I'd wager on cascading failure of plugs. Replace and do the resister bypass mod.

 

[Recovry4x4]

I'd wager on cascading failure of plugs. Replace and do the resister bypass mod.

Before you go spend a bunch of money on glow plugs, check the current flow through the relay. When the relay fails, the card fails to see the current consumption and just leaves the light on seemingly forever. It's a cheap test and if it's the relay, they can be had for $14 on ebay. Glowplugs cost a little more. May as well eliminate one of them rather then taking a chance and ending up replacing the wrong problem. Better yet, get a short length of maybe 10 GA or 12 GA wire. Have an assistant prepare to start the truck. Use the wire to jump across the 2 large terminals of the relay for about 6 seconds then have the assistant try the start. If she lights up, change the relay.

 

[FLINT]

Thanks guys, this is very helpful, sounds like the relay, but I'll go through the test procedure, hopefully soon

 

[FLINT]

She's alive.

I unsuccessfully tried to test the various components, and I was getting desperate to get the truck running, and it was sounding like the glow plug relay was the most likely culprit, so I went to Napa and bought their part number ST85 for $50. Went home, replaced the relay and she started up like a champ - almost sounded happy to be running. The relay now clicks with authority! I'm glad it wasn't the glow plugs.