Glow plugs hot weather

[va350]

A couple years ago and about ten thousand miles ago I replaced all glow plugs and glow plug controller. They work perfect most of the time, the truck fires right up on the first crank even when cold; down in the 20's or teen's. When it is hot; 90's or above and the truck is in the sun the glow plugs do not cycle and I have to crank it a couple times to start. I know if I just by-pass the controller I won't have that problem but my question is shouldn't the glow plugs cycle for a few seconds anyhow? Is the controller bad? My other 87 has the controller by-passed and I manually cycle them for a couple seconds and it fires right up.

 

[IDIBRONCO]

It may be possible that the controller is being "fooled" into thinking that it is warmer than it really is by the sun hitting the hood and raising underhood temperatures. Try parking in the shade if possible. This may help I'm pretty sure that the glow plugs should cycle for a little bit even if it's hot outside.

 

[lindstromjd]

Either that or the sensor in the engine that tells the relay when to turn on is going bad... That should be a relatively easy and cheap fix, and just something to cross off the list of possible problems.

 

[6.9poweredscout]

I wired my GPC to the high idle switch so it doesn't cycle above 116 degrees or whatever it shuts off at. when it's in the sun all day it won't cycle but it fires right off!

 

[Agnem]

Sunshine or not, hot temps or not, it won't matter. The GPC measures the voltage drop across the Z strip. If there is a high voltage drop, then it will keep the glow plugs on until the voltage drop is minimal. That's how it works.

The voltage drop is a function of the quality of your wiring and condition of your glow plugs. The resistance of a glow plug increases as it heats. This will cause it to draw less current, and thus the voltage drop across the Z strip will decrease.

If the light isn't coming on at all, then you have a high resistance connection somewhere in your glow plug wiring. Either that, or your contactor is failing.

 

[va350]

Thanks for the replies everyone. I'll have to check it out when we get back from vacation. We are headed to Maine for a week.