[whiplash]

Gents,

I need a bit of help understanding the glow circuit in my 1999 gu 4.2ltr turbo. I have been having a problem with not hearing the relay clicking off after the glow light goes out. I'm yet to put a multimeter across to see voltage pattern as it may be going on then off straight away meaning I dont hear it turn off because it already is.

Just need to know how the signal from ignition runs to the glow plug so I can figure out where it passes and test those componants.

cheers

Shanon

 

[Dirt Devil]

Hi Shanon, you have two relay's under the gas strut on the right side under the bonnet.
These are the two relay's that work the glow plugs. To test mine I put a wire from the glow plug strap at the glow plugs( or wire to first glowplug) and back to a globe in the cab just to see if it is working and for how long. Dont for get to earth the other side of the globe.

cheers shane.

 

[whiplash]

cheers shane.

I understand what testing i can do i just dont know where the control timer is or where the signal is coming from. Basically what happens from Ignition to the relay. my gregory's doesnt outline the 4.2ltr circuit at all. Multimeter is all I got because im in the middle of the desert as thats where i work. I could make a test light out of my interior light i gues since i have a little bit ofwire in my toolbox. Ill be testing it today after work so that will tell me if the relay is turning on and off and whats going on.

However i still need to understand what is happening from the Ignition power at the barrel to the signal to the relay. Whats in between and where is it. My luck it wont be doing it again I recon as its intermittant, so when i testi itwill be fine.

 

[chubbs]

this is the exact issue im having with my gu td42. the times you dont hear the circuit switch off do you have to crank it for a few seconds longer than usual on a cold start? mine will be fine for few days in a row then the next few i wont hear it switch on and ill have a little difficulty cold starting but once its started it idles fine.

im not all that clued up on these things and i checked the manual i have and it doesnt go into any depth on the glow circuit like your gregory's so ive been meaning to get to the auto sparky but just havent had time so ill be keeping a close eye on this thread.

cheers

-tyler

 

[Dirt Devil]

Hi Shanon, the glow plug timer in in the driver kick panel. When the ign. is turned on the timer will pick up signal from coolant sensor on front left side of motor up top, then if coolant is under 40 deg ( I think 0r 60deg) it will stay on for about 30 sec. if higher than that temp it will go off quicker.
Some GU,s have a resister in the inlet manifold above the oil filters that converts the 11.5v on the first relay ( one closest to fire wall ) through the secend relay to about 5v for the extended time.
I have a switch in the cab to trick the timer into thinking its cold so I can have the glow plugs on for max time when cold.
It is very common for this resistor to short out and the price of them is about $450.00, hence the switch in the cab.

hope this helps.

Shane.

 

[whiplash]

this is the exact issue im having with my gu td42. the times you dont hear the circuit switch off do you have to crank it for a few seconds longer than usual on a cold start? mine will be fine for few days in a row then the next few i wont hear it switch on and ill have a little difficulty cold starting but once its started it idles fine.

im not all that clued up on these things and i checked the manual i have and it doesnt go into any depth on the glow circuit like your gregory's so ive been meaning to get to the auto sparky but just havent had time so ill be keeping a close eye on this thread.

cheers

-tyler

Cheers again shane. I went to test today after work as i dont drive it all day, and guess what the stupid thing worked fine (me hearing it click off). Stupid thing.
Ill have another good look at her tomorrow after work and hopefully be able to pinpoint where im not getting a signal. Do you know what the resistance is for the coolant sensor under 40 or 60 deg?

My model is the basic 4.2 with the 2 different model oil filters and no intercooler. Ill have a look for this resistor your talking about on the manifold as well. hopefully its that thats causing the trouble.

Ill give an update tomorrow night how it goes.

Tyler, my issue is more that i hear the relay turn on but i dont hear it click off after the designated time. From what shane says it is possible the coolant resistor is stuffed and is shortening the glow time to nothing and therefore i dont hear it or it could be inlet resistor making it switch to 5v mode straight away and I dont hear the normal mode of clicking of the relay. I really need to see if im getting 12v or 5v or 0v at the glow rail to see whats happening. Hopefully it does its weird thingo again tomorrow.

cheers

Shanon

 

[chubbs]

yeh same as mine. i can hear it turn on as soon as i switch to accesories but no sign of it switching off. it seems what shane mentioned could be the issue. like yours mine can be fine one day then the next play up.

-tyler

 

[whiplash]

Well got to do a 5 min check last night (was putting beers on for my departure from work). Basically tried it the first time and it didnt do it. tried it a second time and it went straight to zero (0.1V) and didnt hear a second click. So Im gonna have a good look at it tonight after work and see if I can find the cause. Its really annoying because i finish shift at 6:30 pm so I only have like 30 mins daylight to check it out. It wont stop me driving home so I'm not too worried. Just something to do while im in the middle of nowhere.

Oh and my central locking has stopped haha so I think the corregations got to it. Will be sorting that out too tonight.

 

[Dirt Devil]

Sorry dont know the resistance for the coolant sensor, but if you unplug it at the engine it should go into cold start mode. The plugs will stay on for about 25 sec and you will not hear the relay drop out after about 6 sec like normal, so that could be your problem.
I would first try the first relay and see if it is working by putting a hot wire to it from the battery, it will be one of the thinner wires.
If OK I would then unplug the plug on the timer unit in the drivers kick panel, give it a good clean and replug it in.
Hope this helps.


cheers Shane.

 

[whiplash]

Thanks. Ill unplug it then and see if im getting 12v at the plugs. Ill have a play haha

 

[whiplash]

well I tried yesterday but the stupid thing was working fine. Then I tried a few more times through teh night and finally got it to malfunction. Only test i could do was ripp off the coolant sensor to check what voltage i got at the rail and basically when iturn ign on it cranks up the voltage but before teh multimeter stabalises at what voltage it is it goes down to zero. I pulled coolant sensor off and it ramped up to just under 5v.

Do you think this is caused by the resistor you speak of in the manifold. If it was operating properly it should be 12v at the rail right? So basically its making teh relay switch to 5v straight away. Either that or the timer unit itself. I just wish i had more time to be able to check it. Fixed my central locking but so thats a bonus.

cheers

Shanon

 

[chubbs]

well its been a while since any reply to this thread.

i had my ute down to the auto sparkys about a month ago, they tried everything. checked all voltages, glow plugs are drawing what they should. they checked both relays which seemed fine and pulled the timer out of the kick panel and opened it up for a look. they couldnt find anything wrong with it.

$60 and i was off again and the glow system was working perfectly again. i could hear the relay switching off after the 6-8 seconds and bang it would start. a month on and it just started doing it again out of the blue. i was thinking maybe it was a loose wire/connection somewhere?

so back to the auto sparky for a chat, he's going to do some research on it before i take it in again because he's never seen something like it before and has a feeling it may be the temp sensor but doesnt want to be replacing it with a new one because of the price if thats not what is the problem.

i may try unplugging the temp sensor and give it a go but when i ran it past the sparky he thought it could work both ways that it may read its cold without it in or it may read that its up to temp.

he's getting back to me this week so ill update what happens.

any other thoughts?

cheers

-tyler

 

[patrolling]

updates chubb?

had a similar thing happen to my gq td42 today. the solenoid clicks on but not off? anyone know where to get a new solenoid and how to troubleshoot the glowplug system?

cheers,
trav

 

[chubbs]

ive now come to the conclusion from close listening, the relay switches on and off straight away so the plugs aren't getting the 12v straight up but rather the 5-6v for 30seconds-2minutes whatever it is.

im pretty sure its the coolant temp sensor. im going to see them saturday so ill let you know how i go

-tyler

 

[chubbs]

just to elaborate a bit further. i tried unplugging the temp sensor but when i do the glow circuit relay doesn't even switch on so that test didn't lead anywhere.

the one thing im getting now. cold start or been sitting for quite a length of time, like 5hrs +, the first relay is switching on and off straight away so it cranks maybe 2-3 turns to start. if im driving around and switch it off for 20 mins then start again the relay switches on and stays on for the 8 seconds of 12v glow as it would when cold. this only happens when the coolant is right up to temp.

ive come to the conclusion without consulting the auto sparky that the coolant temp sensor is the culprit. im going to go back and see them but im going to price up this sensor. the sparky said on my last visit he imagined it would be $100ish. hopefully not the $450 someone said earlier.

-tyler

 

[petefire427]

Hi all, I have all the test info for the glow plug system and resistance checks for the coolant temp sensor. I will try and put it up tonight(at work atm)

The glow system works (like whiplash said)
It is ECM controlled and has two systems.
Glow mode- When light is on the dash. will operate from 2seconds to 8 seconds depending on coolant temp.
After glow mode- light on dash off, but if the coolant temp is under 60c it will continue to operate untill.... either the coolant reaches 60c or 3mins which ever occours first.

I will put up the resistances later tonight or tommorrow.

I am happy to copy and send the relevent info as well from the factory w/shop manuals.

 

[petefire427]

OK....
Temp sender resistances and voltages.

Temp C volt res( in K ohms)
-10 ### 4.4 ### 7.0 - 11.4
20 ### 3.5 ### 2.1 - 2.9
50 ### 2.3 ### 0.68 -1.00
90 ### 1.0 ### 0.236 -0.260

Taken from Factory w/shop manual- supp vi 1st rev vol 1B
hope this helps

 

[whiplash]

Haha guys im revisiting this issue now. I never got around to solving this isue so will do it this weekend. (Currently in Karratha atm). Im booking a trip away so would likt it to work properly. Now I have the resistances for the coolant sensor I can measure that and determaine the proper cause. Its not very intermitant anymore so can easily solve it. Ill post on my progress

 

[stocky6409]

My 4.2TDI Ute developed a similar issue on a recent work trip. Roads where rough as and now the damn thing wont work when its cold (of course it works just fine when its warm enough that you dont really need it!). I get NO ECM or GLOW light on the dash when i turn the ignition on and the TACHO wont work when the engine first starts....drive off and it starts working and the GLOW light comes on for a couple of seconds. My bet is I have a bad/loose connection SOMEWHERE and I'm going to have to study the electrical diagram at lenght to try and find whats common between the GLOW & TACHO ccircuits as everything else on the dash works fine! Grrrrrr

 

[stocky6409]

Right - found the problem with my ute - luckily easier than i had feared due to its intermittant nature!!!

Above the fuse box in the RH side of the day there are 4 blue relays - 3 mounted on the fuse panel and one hanging of the top edge.

It was that top one (most difficult to get to of course) that was the issue - it wasnt engaging unless you gave it a tap. I swapped it out with one of the others (no idea what any of them do as I dont have a service manual) and it now works - and i know the one i swapped out is the vetilation fan coz now that doesnt work unless you hit a pothole LOL!

Off to nissan for a "gold plated" relay (25230 79981) now i guess......