M1008 glow plug problems

[CBrinker]

I replaced the glow plugs in my truck a couple months ago and it was working great until recently. I‘m thinking my problem could be the glow plug solenoid, but wanted to check here first before spending the money for one. What it’s doing now is I can hear the solenoid click when I press the button (the controller has been bypassed for about a year), but the voltmeter does not go down like it always has while the glow plugs are on and the truck will not start. The solenoid does click on and off with the button, but it seems like the power is not going to the glow plugs. I’m just used to when the solenoid fails, getting no click or I had one get stuck on with a different truck before. I tried searching the forum for anything like this and couldn’t find anything, but I’m not great with the search function so I could’ve missed something. Thanks in advance for any help/advice

 

[cucvrus]

Quick check. Is the current traveling from the top 3/8' stud to the bottom 3/8" stud? Test light and helper needed. Slag build up in the relay can do this. report back.

 

[CBrinker]

Quick check. Is the current traveling from the top 3/8' stud to the bottom 3/8" stud? Test light and helper needed. Slag build up in the relay can do this. report back.

Ok, thanks. I’ll check that tomorrow when I’m at the shop and will report back

 

[joshuak]

Quick check. Is the current traveling from the top 3/8' stud to the bottom 3/8" stud? Test light and helper needed. Slag build up in the relay can do this. report back.

Recently I had to tap mine every so often to keep going until I could replace it. AC has a thread on taking them apart, I'll post up if I find it.

If no helper is around, you can lay the voltmeter on the hood and and wedge the probes of a voltmeter where you're looking.

 

[CBrinker]

Recently I had to tap mine every so often to keep going until I could replace it. AC has a thread on taking them apart, I'll post up if I find it.

If no helper is around, you can lay the voltmeter on the hood and and wedge the probes of a voltmeter where you're looking.

Ok, thanks. I’m hoping I can get my cousin to help me when he gets home from work, if not I’ll just do what you said

 

[dependable]

As mentioned above, the contacts can get pitted and no longer send sufficient current even though solenoid clicks. To make it even more interesting, the condition can be intermittent, and it can also sometimes send a partial current, so sometimes volt meter or even volt meter with a test light will test OK, but it will not be enough to heat the plugs sufficiently for start.

If your dash volt meter is working, one can often tell if contact was completed by position of needle on gauge. It will shift some even when full current is not sent, but will shift more if a complete contact is made.

Since a working solinoid is critical to start the truck, and they are not expensive, I'd suggest you buy a new one. Even if the one you have is OK, a spare is good to have. It is also a fairly common failure.

 

[CBrinker]

As mentioned above, the contacts can get pitted and no longer send sufficient current even though solenoid clicks. To make it even more interesting, the condition can be intermittent, and it can also sometimes send a partial current, so sometimes volt meter or even volt meter with a test light will test OK, but it will not be enough to heat the plugs sufficiently for start.

If your dash volt meter is working, one can often tell if contact was completed by position of needle on gauge. It will shift some even when full current is not sent, but will shift more if a complete contact is made.

Since a working solinoid is critical to start the truck, and they are not expensive, I'd suggest you buy a new one. Even if the one you have is OK, a spare is good to have. It is also a fairly common failure.

It was intermittent for a few weeks and now it doesn’t seem to be working at all. The dash volt meter does work and it doesn’t shift at all when I’m pressing the button anymore

 

[cucvrus]

It is more than likely the relay/solenoid. Did you test it?

 

[CBrinker]

It is more than likely the relay/solenoid. Did you test it?

I haven’t yet, I’ll be over at the shop where I keep the truck this evening to test it

 

[antennaclimber]

Recently I had to tap mine every so often to keep going until I could replace it. AC has a thread on taking them apart, I'll post up if I find it.

If no helper is around, you can lay the voltmeter on the hood and and wedge the probes of a voltmeter where you're looking.

Relay Issue and Repair

 

[CBrinker]

Well I tested it and it tested bad. Got a new one, installed it, and the truck fired right up. It looks like at some point in time someone had replaced the factory one with a cheap, lightweight, plastic cased one. I replaced it with a Napa st85. Thanks for the help and advice

 

[cucvrus]

Cheap plastic ones were what came from the factory. And they weren't that cheap. I have a few that still have that cheap plastic one on them. Clum made them. They are different but nothing inferior about them vs the metal ones. I do buy metal ones now from MurCal www.murcal.com Because that is what Obie Won told me to do. Good Luck. Thank you for keeping us in the know.

 

[CBrinker]

Cheap plastic ones were what came from the factory. And they weren't that cheap. I have a few that still have that cheap plastic one on them. Clum made them. They are different but nothing inferior about them vs the metal ones. I do buy metal ones now from MurCal www.murcal.com Because that is what Obie Won told me to do. Good Luck. Thank you for keeping us in the know.

Ok, thanks for letting me know that. I guess it just surprised me to see a plastic piece like that on there and I just assumed it wasn’t as good. Thanks for the help, it’s always much appreciated