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What the...glow plugs not coming on?

AJMBLAZER

AJMBLAZER

Better to be lucky than good.
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Now this worries me...went to start The Blazer this morning and the glow plug light didn't come on the first two times I tried. It was low 60's so not super hot or anything. Truck chugged but no start. About half way through the second attempt the glow plug light came on while I was turning it over. Stopped, waited a moment, turned the key again and the light came right on and then when it went off the truck started right up.

WTF?:confused::doah:
 
This isn't uncommon. You could just add in a manual button for the short term, but there may be a connection that needs to be cleaned, or a temp sensor going bad.
 
I figure this will probably keeping getting worse and eventually it won't work?

Which sensor(s) would be going bad?
 
Can't remember if I have the Haynes or Chilton but it has a relatively simple diagnostic chart to go through to check for glow plug issues.

If the temp sensor is bad (as in stuck at high temperature) it will not allow the glow plugs to come on when the engine is cold since it thinks the engine is warmed up.
 
It worked fairly well last week for me on the drive. Then again it was cooler on most of my trip. Only the last few days has it started behaving a bit odd...but this was the first time for this particular quirk.
 
It's been a few years since I had to mess the sensor, but if I remember correctly if you simply unplug the sensor it gives the "cold" signal (open = cold, closed = hot). So if the plugs won't come on when the truck is cold, simply unplug the connector and see if that fixes the problem.

This is the temp sensor located on the front top of the engine.
 
Of course with his motor being an '89 it could be slightly different too... though I was thinking my temp sensor was in the rear of the head ('83 model).
 
Did it again today.

Upper 70's and humid as hell after work. Truck hasn't run since 7:30am so just about 9 hours of sitting. I turned the key there was no gp light. Let it sit and cranked it. Chuggachuggachuggachugga... Tried that several times and nothing but the same chuggachugga. Unplugged the sensor on the front of the engine I think you're talking about. Didn't seem to make a difference. Plugged it back in, tried again after it sat for a minute or two. ChuggachuggachuggachuggaVROOOOOOM and it caught with a big cloud of smoke. Still no gp light though.

Drove it home. Hope it starts in the morning, have a vet appointment at 9am.

Is this the correct sensor?

is this the temp sensor.jpg
 
can't answer your question as to if that's the sensor or not - i know on older models at least, it was a big cylindrical thing that stuck up out of the driver's side head at the back.

if you can't get your gp's to operate w/ the switch, you can jump the circuit with a short piece of wire. i've done that in a pinch a few times. the gp controller is on the drivers fender, and if you jump the terminals with a piece of wire, you'll get them going just fine. you just need to somehow get power to the gp wires - there should be 2 coming off of the controller. so, if in the morning it doesn't work - just jump the wires across for about 8 seconds or so, then fire it up and you're good to go. ;)
 
I thought the controller was on the back behind and below the air cleaner next to the firewall?

At least that's where the thing that looks like the Chilton's illustation is.

Is there a CK5 manual gp switch write up?

The weird part is that once again it works fine. Got in it about 8 to go down to the store and the gp light came right on. Drove about 3 miles to the store, went in for 5 minutes, and when I came back out the light came right on and the truck started up just fine.

Oy...
 
Yeah, on the later models it's on the rear of the driver's side head. there will be a five pin ? connector and two fat wires on studs. Jump across the two studs. Easy as pie :D
 
Cool, thanks.

Can anyone confirm that the thingy I was pointing at is the sensor that 6.2 mentioned earlier?
 
Mine may be different but...

I have another temp sensor down on the side of the passenger side head, at the rear. The wiring for it was shot and kept blowing my gauge fuse causing me not to have glow plugs or gauges. I only found it by replacing the fuse with a circuit breaker and waiting for it to start smoking! I have not replaced it yet, just unplugged it and wired my gp's manually. However, this also causes my cold start advance not to work on the IP. My truck is an 84, so I think the gp system is different.
 
I've never had a newer one like your fancy truck... can't tell you if that is the correct sensor. You might want to start looking for a factory service manual with a good wiring diagram.
 
Yeah, I know. Got one I'm watching on Ebay but $$$ ya know?

The Chilton's I have does have a decent write up but the diagrams are about worthless. Tells you what to do but not where anything is.
 
yeahh i think its all about wire tracing, sounds like a bad connection or ground. I know its not a cucv but post over on SS if you havnt already, i mean thats practically a diesel forum for obvious reasons heh, so someone may know something there too, good luck
 
The glow plug controller is on the back of the engine, but there should still be a glow plug relay on the drivers fender...no?

Rene
 
Dabba said:
yeahh i think its all about wire tracing, sounds like a bad connection or ground. I know its not a cucv but post over on SS if you havnt already, i mean thats practically a diesel forum for obvious reasons heh, so someone may know something there too, good luck
Click to expand...
Eh...not a big fan of that place since CCATLET left. Pretty unfriendly folks and the way they treated kennyw just for disagreeing with them...:eek1:
Besides, there's a bunch of guys there who know a lot about CUCV's and jack about 73-87 GM trucks. I ask questions about the milspec stuff on Big Ugly there but that's about it anymore.
tRustyK5 said:
The glow plug controller is on the back of the engine, but there should still be a glow plug relay on the drivers fender...no?

Rene
Click to expand...
No clue. This weekend turned into put the AC in the house Saturday and not feel good Sunday. I started on the t-case rear seal way too late today and by the time I was starting to dick with the rear u-joint to drop the shaft and yoke the headache had turned into a trained monkey with a base drum and sense of rhythm. I put it back together, packed it up, and crossed my fingers.
Hopefully it works tomorrow.:crazy:
 
Oh, I should mention that it started fine today and I noticed the relay does cycle when the light works.

Then it did something odd. After it started the gp light came back on for just a moment.

Just throwing this stuff out there.
 
after the truck starts, the glow plugs will cycle on and off to help combustion till the temp sensor decides that it's time for the gp's to stay off altogether... i think. my buddy's 6.2 did that alot.
 
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