Last winter I replaced the glow plug relay because I was having hard starting and determined that the relay wasn't passing current.

In the last few weeks we have had fairly cold weather here. In my neck of the woods, below freezing is "fairly cold." I added a LED to monitor my glow plug circuit after last year's problem.

Sometimes, but not regularly, when I go to start the engine while cold the LED will flash for a split second, then go out. Of course, the truck doesn't start well when it does this. I have discovered that if I cycle the key full OFF, the light will come on when I try it again. Sometimes I have to cycle the key four or five times.

While it could be another bad relay, I kind of doubt it, since in my experience relays tend to die completely, rather than intermittently.

I know that the PCM does not order the GPR to engage if the oil temperature is above a certain level. I wonder if my oil temp sender is telling the PCM that the temp is too hot to need the GPR to engage?

Has anyone had a similar problem?

Having the LED is allowing me to keep using the truck while I figure this out. It is well worth the very small investment in time and money!

 

It still could be a bad relay. When the relay makes contact the current draw is pretty high. Have you tried listening to the relay or feeling it when the key is turned on? I had a guy bring me a truck that the relay was solidly engaging but the no voltage to the GP's.

I tore it apart after swapping it out and found the post to have arc damage. This would not pass the current to the GP's.

 

subscribing. I may be having the same issue. Just replaced GPR. we'll see.

 

First I'll try swapping the system over to the AIH relay. That should isolate the relay as the problem.