jrsavoie
08-04-2007, 01:43 PM
My 1989 GMC truck is hard starting when warm. It starts fine cold and hot but when it is in a certain temp range it starts a little harder.
I'm sure the glow plug controller is not activating due to being told that the engine temp is sufficient and glow plugs are not needed.
Any ideas?
It has been this way for several years.
Sometimes the glow plugs are needed when the engine is hot. If the glow plug inhibit switch malfunctions it can cause the plugs to stay off when they are still needed. Common problem.
Other times this is due to a worn injection pump. The only fix in that case is to get another pump (or repair the one you have).
jrsavoie
08-04-2007, 06:52 PM
Sometimes the glow plugs are needed when the engine is hot. If the glow plug inhibit switch malfunctions it can cause the plugs to stay off when they are still needed. Common problem.
Other times this is due to a worn injection pump. The only fix in that case is to get another pump.
The truck will start hot and cold but in between it starts harder. You have to crank it over longer than I like.
Where is the glow plug inhibitor switch and how can I bypass it?
Thanks
As I recall it is on the rear of the passenger side head. Bypassing it is simple. Cut the wires that go to it and splice them together.
SMITH6.6
08-04-2007, 07:31 PM
one thing you could try is when your having the problems dump cold water on the injection pump and see how it starts, if that made it start easier you need a new head on the injection pump that is a common problem
Careful about doing that. If you cool the IP with water it is possible that it will sieze. If you then crank the engine you can break the pump driveshaft and ruin the IP.
peyton
08-05-2007, 02:43 AM
As I recall it is on the rear of the passenger side head. Bypassing it is simple. Cut the wires that go to it and splice them together.
Rather than bypass it, why not just put a normally open switch across the leads to the sensor. Then you could force the glow plug relay only when needed.
Peyton
You could do it that way as well. I prefer to bypass it because I don't like extra switches to deal with and I don't care if the glow plugs come on all the time. When the engine is hot I ignore the glow plug light and crank the engine.