My 92 Chevy 6.2 truck 's glow plugs will turn on when the motor is cold but when I drive it and shut it off for a little bit and come back out before the motor has cooled back down the glow plugs don't always kick on and I can't get her to start again. But if I jump the leads on the solenoid for about 6 secs it will start right up. Anybody have any idea on what is causing this and how I can fix it. :(

Can be a few things, but one thing comes to mind quickly. There is a temperature inhibit switch located on the passenger's side rear head. Its a sensor mounted on the blockoff plate on the back of the head, it will be a two-wire connector. What I've done is cross the wire with a jumper in the connector after disconnecting from the sensor.

You might also take note of how fast your engine is cranking over when it's warm and won't start. If it's cranking slow, its time for a renewing the connections at the batteries, or battery replacement, and finally starter replacement or repair.

And finally, the other thing it could be (being a 92) is the injection pump head could be failing (I had a 91 with this problem) that wouldn't start if it didn't get a glow when luke warm engine temperatures. It became worse and worse about it until I had to rebuild the injection pump only to get another bad one, that was found when testing the reman! Anyways, your glow plugs don't always have to come on to start, it's when they don't when warm that the ugly problems with the engine start to show up.

We have already installed new batteries (he just got done redoing the whole truck) the cables all tested fine, the injector pump was redone, and the starter is working fine. When the glow plugs work it starts up better then my 6.5 does (I believe it needs a new starter). We think it may be the controller. He did the jump thing and the glow plugs would kick on but they didn't stay on as long as the manual says they should. and then when he disconnected a wire (I think the glow plug wire) the glow plug lights still came on.

Your glow plugs should not be coming on when your engine is warm. If your glow plugs come on when your engine is cold then your controller (on the left bank) is working and the thermostat (on the right bank) is working. The thermostat on the right bank will not pass current to the glow plug relay when the engine is warm. Sounds like your system is working as intended.

Normally when your engine starts when it is cold, but not when it is warm then the injection pump is not putting out enough pressure to the injectors. The fuel is not atomizing good enough for combustion under compression. If you manually start the glow plugs then the heat of the glow plug will ignite the fuel even though the atomization is not as it should be.

If you have Delco 9 or 11G or Champion 17 glow plugs then you had better be careful or you will get mushroomed tips due to the tips getting too hot. And please don't use ether or starting fluid to start the engine because you can cause engine failure.

In the manual even if your engine is warm your glow plugs kick on just not for an extended period of time like they would if you engine is cold. When the light kicks on the engine starts when the lights don't kick on it doesn't start and he has to mess with the wires to the controller to get the light to kick on then he is able to start it. If the truck didn't start well when the glow plugs were turning on then I would consider the injector pump but it is a newly remaned injector pump so I highly doubt that is the problem. He is really leaning toward it being the controller box.

I have run into this before. In 93 I believe that the thermal limit switch had been eliminated due to hard start when warm conditions. I would either replace the controller or save your self some aggrivation and wire in a manual glow plug switch. It is very simple, inexpensive and only takes about 30 minutes for install.:rolleyes:

I have run into this before. In 93 I believe that the thermal limit switch had been eliminated due to hard start when warm conditions. I would either replace the controller or save your self some aggrivation and wire in a manual glow plug switch. It is very simple, inexpensive and only takes about 30 minutes for install.:rolleyes:
Can you tell me how to do this? Nathan has the stuff that he could do it himself without needing a kit. How do you bypass

Diesel Chick,

I will start with a little theory of operation to help you understand what you need to accomplish. The glow plug controller is basically a smart switch. It has a 12v feed line going to it and when energized, sends 12v to the glow plugs. So, there are two large studs, one with power in and the other with power out. The controller determines how long to supply the power to the glow plugs. To make a manual system, you simply remove the wires from these two studs and in turn hook up these wires to a 12v solenoid. I prefer to use the solenoid from a 83 6.2 glow plug circuit because of the way it works. The solenoid has two large studs and two small studs. The 12v feed line goes to one of the large studs and the glow plug feed line goes to the other large stud. Mount the solenoid in a place where your existing wires will work,(you might have to make a small bracket or possible attach to an existing bracket) Next you need to run a 12v keyed hot wire to one of the small studs. The last wire to hook up needs to go to the other small stud. It needs to be routed through the firewall to the dash and connected to a push button starter switch. The switch will have two terminals. The other terminal needs a wire that goes to a good ground. With the key on, push the button, the button completes the circuit to ground, thus energizing the coil in the relay and connecting the circuit and making the glow plugs heat. The glow plug wait to start light should come on once the circuit is energized. I recommend using A/C 60g glow plugs(they are very resistant to burning out and won't swell) Hold the button from 10 to 20 seconds when the engine is cold and about 5 seconds when the engine is warm. When the engine is cold, you can give a little after glow after the engine has started, by holding the button for several seconds and then releasing, repeat as necessary until the engine smooths out. Other solendoids can be used, but different solenoids opperate differently. The type I recommend is energized by grounding one of the small terminals. Other types can work by supplying power to a terminal and vary with the type. There are many different types of solenoids and they all share the same principal but accomplish it in a slightly different way. Hope this helps, feel free to ask more questions if needed and let me know how it works for you. I have used this system on all of my 6.2's and 6.5's including my daughters 86 6.2 that I just did several weeks ago.:grd:

Thank you very much - I will pass this along to Nathan (BF/mechanic) because unfortunately for me I really don't know what half that means but he will. Thank you again!!

GM and AC Delco catalog show this relay as "Part # 560580". You can view it online in the AC Delco website. It was used on the early Olds 5.7 diesel engines as well as the early 6.2's.

When my glow plug solenoid failed about 17 years ago, I put in a spare Ford Pinto solenoid. It is only slightly larger than the 6.2L unit, but it has lasted about three times longer and still hasn't failed. Any small car solenoid should work.

I don't understand any manual stating that the glow plugs should come on when the engine is warm!!! There is a thermostat switch in the glow plug controller on the left bank and the wire going to the glow plug relay on the solenoid goes thru the thermostat control unit in the right head. When the engine is warm then the thermostats open thereby preventing any current passing to the glow plug relay. Both thermostat circuits have to be closed for current to pass.