Glow plug cycling

[MM9135]

My 6.5L with 98,000, now that the mornings are cooler, is doing something different. I have only owned this vehicle since August and this was the first time I noticed this. My "wait to start" light goes out and I crank her over and then it starts right up as always. However, within a few seconds the light will come back on and then off and then on again and off. Is this normal in cooler weather for the glow plugs to come on after the engine starts?

Also, when the engine is running and the light comes on my voltmeter drops down to 9 volts and then swings back to 14 every time the light comes on and off. Sounds like there is a bad (high resistance) connection somewhere maybe??? I had the alternator checked and it is charging fine. Any input??

[Simzie]

The cycling of the glow plugs after startup is a normal function as well as the voltage drop. Keep in mind eight glow plugs do draw a lot of current to get them to glow a cherry red. With the mileage that you have, do you know the history of the glow plugs? have they been replaced? If not you may want to consider this soon as for when they fail they have a tendancy to swell and are very difficult to remove. My 98 6.5 cycles the glow plugs no matter what the outside temp is, sometimes more as the temp drops. Dont be alarmed but definetely check the age of those glow plugs. Simzie

[MM9135]

Thanks for the response.

I believe the glow plugs to be original. This truck had the bare minimum of maintenance in it's earlier life. I looked at them the last time I had the engine cover off, this is a van, and they looked pretty old.

They looked so small I was afraid to touch them for fear of twisting them off. Is that a high possibility? Since they were working I was going to leave will enough alone.