Glowplug carbon buildup
 

I've had my gpr disconnected since last winter. I was reading recently on another forum that doing this can cause carbon buildup since the gp's never burn it off. It makes since but I just wanted to see if anyone concurs with that statement. I figured there is that possibility or the heat of the cylinder would keep it burned off. Getting cold again...think I got everything now to try putting it on a switch and led indicator. I plugged the gpr in the other day and my truck is very noticeably harder to start than if the gp's were not engaged. Weak starter? Batteries are about 3yrs old. Truck starts fine without gp's and alt charges batteries up to 14.2v running. And terminals are tight and spotless. Would load test reveal the health of the batteries even though they hold a charge?

The load test should help.