Glow problem, not the relay though

[nathan71]

My glow plugs will not cycle when the truck is hot, and it won't start w/o them. Had the same problem a few years ago, replaced the relay and fixed the problem. Same situation now, just replaced it, still acts the same. What else should I look at. Could it be the sensor in the t-stat housing? If so, anybody have a Napa part no.?

[BobND]

You could try (carefull not to damage the little connectors) to jumper accross the switch and see if that helps, but I believe that switch is just for the HPCA. If jumpering around the switch DOES help, (and doesn't affect the HPCA) you can leave the jumper in place, IF you're running 60G's, or other dual-coil glow plugs, glow plug life will not be affected noticeably. Also, check at the back of the RH cylinder head, where there is a block-off plate over the head's unused water port aft of the intake manifold. The earlier 80's units had the glow plug inhibit switch there.

At some point, GM dispensed with the "inhibit glow plugs when warm" switch altogether, but I can't recall what year.

Quite a few of us, with the pre-1994 glow plug system, are running the dual-coil glow plugs, and have moved the controller to the left fender, and installed a resistor to give added glow time (per Dr. Lee).

A search of the archives will turn up the details on the value of the added resistor.

I have been running several vehicles for a couple of years with these mods. Glow plug life with the 60G's has been good outside of one set the had a couple fail quickly. Their replacements, and a couple of other sets are lasting well.

You simply cannot believe, until you've done it, what a difference moving the controller away from the engine heat (so it comes on with the motor warm), and adding the resistor to increase glow time makes. Cold starts are much improved, and hot starts are much quicker, with way less smoke.

However, DO NOT move the controller, or add the resistor without the dual-coil glow plugs! The 9G's or 11G's (or similar competitive units) will swell and break, causing engine damage!

(Starting with 1994, when the ECM took over control of the glow plugs, they are always cycled, even on a warm engine.)

[DmaxMaverick]

First, take the advice to NOT make adjustments to the GP system if you have 9G plugs (or aftermarket equivelent) installed. They are very sensitive, and can/will swell when they fail.

If the plugs cycle by jumping the controller, like you would a starter solenoid, the problem is likely the temp sender.

If it helps, there is a diagram of the circuit at my "truck stuff pic's" in my sig. under diagrams. Page 5-42 shows the circuit in detail in the lower-left area of the page. There is also a fusible link involved, so make sure it is not causing a problem, as well. Double check all connections and ground points, to be sure you aren't chasing a ghost.

[wthif]

Originally posted by IUPAC:
My glow plugs will not cycle when the truck is hot, and it won't start w/o them. I know you want to fix your glow-plug system and you should, but if you have the means you should have your truck timed. Timing your truck will help with hot starts. A correctly timed truck should start with out glow-plugs when hot. There are other factors than timing that will effect hot starts, but it is nice to be able to jump in your truck and just start it.

[nathan71]

Thanks for the help. You're right it would be nice to be able to start it w/o glow. I have other plans for it, but I want it more reliable for the time being. I'll check out those suggestions.