Glow plug cycle explained.

[Matt65]

I am not sure that my glow plugs are going through the correct sequence during startup. Here's what's happening:

Switch on, Wait light on. I believe I can hear the glow plug relay engage. With the engagement comes corresponding voltage meter fluctuation - Lower when on, then higher when off. All this occurs within the yellow range at minimum. The wait light goes off, the relay clicks with its disengagement and the voltage rises. The key is turned to start, the starter engages, and the engine starts.

From this point I am unsure of what is happening. Once the engine is running the same click that I hear with the wait light will click on, and then off. With this clicking comes the same voltage meter fluctuation. At an overall higher voltage due to alternator input, but the same sequence that was observed when the wait light was on. After 2-3 times of click on, click off the clicking will stop and the voltage will stay high in the green. The wait light never comes back on after engine startup, and only during the initial cold start of the day.

Despite my unsuccessful reading of manuals there is a strong likelihood that this is covered at some point that I have not yet reached. If this is the case please point me in the right direction.

 

[mtjbrown]

Mine does the same thing, I hope there is nothing wrong. If I try to move my truck before the clicking sequence ends, the alt. belt really squeals as I move the truck. I just let mine go through its sequence and then its fine for the rest of the day.

Mark

 

[acmunro]

Sounds normal to me. Glow plug cycle after the engine is running is an effort to reduce exhaust emissions from a cold engine.

 

[T_F_E]

Yeah your motor is suppose to do that, very common.

 

[Matt65]

Thanks for the feedback guys. Glad to hear that nothing is out of the ordinary. I have been reading about all the glow plug related issues and wanted to make sure. I like to know that they have turned off for good before I hit the road.

 

[acmunro]

The volt meter is a good reference. If they don't cycle more than 2 or 3 times after the engine is running all should be good.

 

[Matt65]

The volt meter is a good reference. If they don't cycle more than 2 or 3 times after the engine is running all should be good.

Thanks.

What is the most common failure: Steady on till they burn out, or a repeated cycle on and off for far too long?

 

[Keith_J]

After glow is the turning on of the glowplugs after the engine is running to warm the precombustion chamber. Like stated, this reduces emissions by decreasing ignition delay. But it does increase idle noise.

It also increases the load on the engine, since the injection pump is also a governor, this reduces warmup time. Any increase in electrical load increases the load on the engine. My civie diesel has 3 additional glow plugs in the coolant jacket for this exact reason.

 

[jwaller]

it also helps to reduce buildup of crud on the glow plug itself.

 

[Mudstone]

im certain my plugs are working... yet i no longer hear the clunk they used to make... anything to be worried about?

 

[acmunro]

Thanks.

What is the most common failure: Steady on till they burn out, or a repeated cycle on and off for far too long?

I can't say on this one. I have had extended glow times and constant cycle high freq on off cycles. I always caught them before glow plug damage occured. I guess that is why most CUCVs have a couple of things hanging under the dash a starter relay (a whole other topic) and the glow plug card recptacle. Both easy access to unplug quick in case of failure.

 

[jakwi]

I ran a wire from the glowplug side of the relay as I suspected that my relay was sticking, I connected that wire to a small 12v bulb (as my m1009 was converted to 12v by the po). I'm not certain that mine works the way it is supposed to, but I think it does.

Turn the key on the wait light and my new gp light come on. wait light will then go out 10 sec later depending on the temp, but the gp light will continue. Start the engine and the gp light will continue for another 10 or 15 seconds. Under normal circumstances that's it. Only once did it come on after it had shut off and the engine was running, it was really cold out, and it just blipped on for a second. Anyway just wanted to contribute my experiences.