burnt glow-plugs/bad controller?

[C.K. Piquup]

On my`91Sub I noticed the glow-plug light flickered and I could here buzzing(very faint).This happened a few times out of dozens,then one time the light just stayed on(without buzzing)for an extended time,after running,probably the better part of a minute.Now,a while later,it won`t start(unless plugged-in/@50-60deg.)I`m thinking the controller`s gone or is going/then went the glow-plugs,right?

[CleviteKid]

Has the glow-plug light on the dash quit working too? If so, the controller is not happy.

Have you tried pulling the connectors to the glow plugs off, then checking ohms on the plugs, each one should be around 1 ohm if good, infinite or zero ohms if bad (probably infinite, much less likely zero).

When I first got my truck, way back in 1991, it needed to be plugged in below about 50F to start. As I learned about glow plugs, I discovered that six of them (Champion junk) were burned out. Controller still worked fine, just did not have many assests to control.

Dr. Lee :cool:

[C.K. Piquup]

Yeah the light works.All this flickering,buzzing,and staying on occurs once engine is running.And now that it doesn`t start,it will only start when using engine heater,even with warm weather,and then with alot of cranking.When it fires,it has lots of fuel to burn from longer cranking.Does the controller know if extra cycle-time is needed when glow-plugs are failing?I know glow-plugs are like dominoes when they start to go till the last one(s)can`t do it at all.

[CleviteKid]

Do you have, or can you borrow, a multimeter to test each glowplug for continuity and for resistance? You can test for continuity with a 12 volt light bulb, like a tail-light or dome light bulb, cheap socket from the cheap auto parts store, and some wire. From the + 12 V terminal of the battery, one wire to the bulb in its socket, the other wire to each glow plug tab, after the wire has been pulled off. If the light bulb lights, there is at least continuity thru the plug. If the light is very bright on some plugs, they might be shorted out to ground.

Sounds like you need to start saving for a new glow plug controller. At least they are cheaper than the thermo-mechanical nightmare that came on my 1984 originally.

Dr. Lee :cool:

[dieselbegreat]

C.K.:
It's fairly obvious that your glow plugs are fried because of the failure of your glow control system allowing them to remain energized too long once. The first thing I would do is replace all 8 glow plugs with AC 60G so they won't burn out. Check out http://www.62-65-dieselpage.com/members/8593GLOW.HTM in the members' section. If your pin voltages are correct and constant to the controller, the controller is just bad so replace it forthwith.

[C.K. Piquup]

I do have a simple test light,should get multi-tester,though.I`ll check this out soon.So 60Gs are that much better?I posted this topic for that reason.Didn`t want to burn-out new plugs/didn`t want to buy controller unless needed.I hear you,Doc,on the`84 system.My Helm book didn`t even have the inhibitor switch in the trouble-shooting chart.Once,I fryed a brand-new,yet to be paid for,controller the second I turned the key(before a fuse could blow).I also kept finding shorts in the wiring,which was the culprit that time.I was about to replace the under-hood harness.Then a friend(farmer)bought it and just did a manual switch.

[C.K. Piquup]

I picked-up 60Gs and controller today.I requested the 60Gs,Partsman said that is what was listed for my`91.I haven`t pulled old plugs yet,so I don`t know what it`s had in it.Are they(GMparts) just offering the new and improved 60Gs for all replacements?Or,would they have come in a`91?Just curious.Thanks again for replies.

[dieselbegreat]

The 60Gs are fairly new on the scene, maybe about two years. They are not supposed to burn out like the 11Gs you probably have in there. There are reports IN SOME CASES that the 60Gs do not seem to heat up as fast as the old style plugs so some people stick a 5 ohm resister on Pin C of the controller to add glow time, especially in the winter but don't worry, they are much more dependable than the old ones especially if your controller fails again.

[C.K. Piquup]

Got the `Burb up and running again.Never did any testing,the problem seemed pretty obvious,as supported by your replies here,thanks.The 60Gs have 1995 printed on the box,so that that would be the year of introduction.So,I guess when you ask for G-plugs at the dealer that`s what you get now,smart move.Only had one tuff one,the last.I came out with needle-nose Vise-grip clamped on hex and a pry bar.Alot of loose soot on three.