Glow plugs cycling after start.

[NorthPatrol]

It began with my M1009 running and starting fine until it got cold out. When the weather turned cool it did not want to start. I noticed that even though I could hear the glow plugs cycle on and off the voltmeter would not move. I checked the glow plugs and found that 7 of the eight were bad.

I replaced the Wellmans with AC60G's and changed all of the connnector to fit the 60G's. Now the plugs cycle and the truck starts right off. My question is about the cycling. I noticed that when it started the plugs would cycle for quite a while. They cycled until the fast idle shut off. They clicked and the voltmeter dropped with every cycle.

I've heard that they cycle for a little bit when first running. This seems a little long to me. What is a resonable amount of time for them to cycle? If this is not normal what could be causing it?

As a side note I checked the GP's in my International 706 tractor and found that they were Wellmans. (granted one was burned out)

 

[CCATLETT1984]

they will cycle on and off until the controller thinks the truck is warm enough to be firing on all cylinders (I'm not sure if its timed, never bothered). Them cycling on while the engine is running wont harm a thing.

 

[NorthPatrol]

Thanks for the quick reply. I understand that they will cycle on and off a few times when the engine starts. I do this with the manual setup on my other diesels. What worries me is how much the where cycling. They did it for about a minute or more every couple of seconds. That means they cycled about 20+ times.

Just concerned and was wondering what was normal.

Thanks.

 

[CCATLETT1984]

cycling on and off will not harm them at all. the only thing that harms GP's is leaving them on for extended periods of time.

 

[cjkeeliii]

I have a similar problem that has been occurring for the past month and a half. After the high idle solenoid turns off, the glow plugs continue to cycle--this is a new occurrence for my m1008. I replaced the glow plugs with ac60g's about a year ago. Sometimes the glow plugs won't cycle but the high idle will activate and vice versa. The high idle used to always activate and the glow plugs cycle--just for shorter periods in warm weather.

 

[Crash_AF]

The glow plugs cycle after start up to help improve the idle of the engine and reduce smoke during warm up. There is a temperature switch on the back of the block by the driver's side head that controls the glow plugs. Until this switch tells the controller that it is warm enough, the controller will continue to cycle the plugs.

It will not hurt anything unless they continue for a long time (over say 5 min) while driving.

Later,
Joe

 

[NorthPatrol]

Thanks for all of the input guys. I know I'm just being a little paranoid, but what the heck. It doesn't hurt to get a couple of other opinions.