LJ70 glow plug issue (1 Viewer)

[Ceckus]

Hello. I tryed to find information, but I can't find anything so I will ask here. So, I have 1986 LJ70 model (Euro) and I can't find where is the problem. The previous owner made some damage to car installation, that alternator could run 18 volts instead of 12v (I don't understand sense of this mod) . Because of that big part of car equipment were burned. I fixed installation, all burned devices. But I can't find problem with glow plugs system. As I understand, this car has "super glow" system. It doesn't work. I tried to measure voltage on buss bar, and get 0 volts. When I tried to check to the connector on this part Photo by Mark Cullen (i didn't know how it's called, so I attached photo) I found out there's 6 volts. Can anybody tell me, what's bad with my car system? I changed timer, main relay, glow plug relay and glow plugs. Sorry for the bad english, I'm from Lithuania

 

[saw]

Hi, I`ll try my best based on what I learned when I fixed my LJ73.

This is the superglow system:

If it works like it should it`s something like this:

Ignition on, Cold engine, no.: 1 glow plug relay puts 12V to the glow plugs for a few Seconds, typical 2-5 seconds, time is based on water temp sensor. The glow plugs are ment for 6V so they heat up superfast when 12V is put to them. Then the system switches out relay no.: 1 and in With relay no.: 2, then the voltage drops to 6V because of the glowscreen which is put in series With the plugs. This is a big screen in the intake not a glow plug. Then the system stays on for some time, again based on water temp but typical 20-30 Seconds.
If you try to glow one more time right after the system will not put 12V on the plugs, just 6V this is to prevent damage to the glow plugs because they are already pre-heated, you have to wait some time to "reset" the system and this makes it quite "tricky" to troubleshoot.

Check:
Fusible links, relays, glow plugs, water temp. sensor, and of course all Connections including the Earth. Make sure the glow plugs are the correct ones meant for 6V, if not the system will not work properly.
Troubleshoot tip:
If the system detects defect glow plugs it will skip the 12V part and og directly to the 6V. You?ll just hear the clicking in and out of relay no.: 1. (If I`m remembering correct.)

The pic you linked to I think is the glow plug current sensor.

(Norwegian DIY guy, no expert.)

 

[TrailRunner40]

I have a BJ70 and had similar issues with the glow plugs. I tinkered around with it for a bit but instead of replacing those expensive parts, I installed a Wilson switch and love it. Takes less than an hour for a clean install and is guaranteed to work.
Buying all new parts and wire from Amazon, it was less than $30 USD.

 

[fred777]

Hi, I`ll try my best based on what I learned when I fixed my LJ73.

This is the superglow system:

View attachment 1884719

If it works like it should it`s something like this:

Ignition on, Cold engine, no.: 1 glow plug relay puts 12V to the glow plugs for a few Seconds, typical 2-5 seconds, time is based on water temp sensor. The glow plugs are ment for 6V so they heat up superfast when 12V is put to them. Then the system switches out relay no.: 1 and in With relay no.: 2, then the voltage drops to 6V because of the glowscreen which is put in series With the plugs. This is a big screen in the intake not a glow plug. Then the system stays on for some time, again based on water temp but typical 20-30 Seconds.
If you try to glow one more time right after the system will not put 12V on the plugs, just 6V this is to prevent damage to the glow plugs because they are already pre-heated, you have to wait some time to "reset" the system and this makes it quite "tricky" to troubleshoot.

Check:
Fusible links, relays, glow plugs, water temp. sensor, and of course all Connections including the Earth. Make sure the glow plugs are the correct ones meant for 6V, if not the system will not work properly.
Troubleshoot tip:
If the system detects defect glow plugs it will skip the 12V part and og directly to the 6V. You?ll just hear the clicking in and out of relay no.: 1. (If I`m remembering correct.)

The pic you linked to I think is the glow plug current sensor.

(Norwegian DIY guy, no expert.)

Hello. Your post is very interesting. I own a LJ70 from 1988, I have an issue with the pre heating system. I can't get the 12V pre heating, I only have the 6V pre heating. I can hear the glow plug #1 clicking in and out. I have 6V at glow plugs, that's it. My 2 relays work fine. My 4 glow plugs are brand new (6V).
I bought a pre heating timer, replaced it, same problem. I can't find the temp sensor, it seems to be well below the engine. Have you got any clue about what could be the problem ? Thks a lot ! Fred

 

[Houser]

There are no mysterious intersections between the 12v relay and the glow plug bar. Just a wire. If you have 12v in and 12v out but no 12v at the glow plug bar the wire is broken.

 

[Squash]

Try unplugging the water temperature sensor.
My old BJ74's glow system hated mediocre temperature and would not cycle in the 0 Celsius range. At -20 C no problem!

 

[fred777]

Hi all,
I have made some more investigations :
on the LJ70, there are 2 glow plug relays. one is followed by a resistor to provide 6V (relay #2 on the plan above) and the other one (relay #1) is providing 12V.
after testing, it looks like relay #1 (which should provide 12V) is not receiving 12v command but something like 11V decreasing slowly. so the relay is clacking on/off just after contact in. and doesn't provide 12V. So I have 6V on the bar from relay #2.
It may come from the relay #1 command cable.

Both relays work fine. I have tested them.

I also suspect a problem from the temp sensor.
But I have no clue where the temp sensor is. it is hard to see it below the wires and on the side of the engine, full of black grease...
How do you access to the temps sensor ? I didn't find any tuto on the web

 

[Eurasiaoverland]

Temperature sensor is towards the back of the engine (between cylinders 3 and 4 I think), below and behind the intake manifold.

 

[fred777]

Hi all,
I have made some more investigations :
on the LJ70, there are 2 glow plug relays. one is followed by a resistor to provide 6V (relay #2 on the plan above) and the other one (relay #1) is providing 12V.
after testing, it looks like relay #1 (which should provide 12V) is not receiving 12v command but something like 11V decreasing slowly. so the relay is clacking on/off just after contact in. and doesn't provide 12V. So I have 6V on the bar from relay #2.
It may come from the relay #1 command cable.

Both relays work fine. I have tested them.

I also suspect a problem from the temp sensor.
But I have no clue where the temp sensor is. it is hard to see it below the wires and on the side of the engine, full of black grease...
How do you access to the temps sensor ? I didn't find any tuto on the web

Well, I have made a test on Relay #1. I have sent him 7V, and it is working fine (click in/out OK). So the problem doesn't come from the command line. I guess that as soon as the 12V command is sent to the Relay #1, the command stops sending 12V. why ? an earth issue somewhere detected by the timer which then stops ordering 12V to the glow ?...
any suggestion ?

 

[fred777]

Temperature sensor is towards the back of the engine (between cylinders 3 and 4 I think), below and behind the intake manifold.

ok thks !
how do you access this ? do you have to remove some items from the engine first ?

 

[Eurasiaoverland]

ok thks !
how do you access this ? do you have to remove some items from the engine first ?

It is years since I did this job, but with a deep socket and a univeral joint it should be doable without removing anything. If you take the intake manifold off it will be much easier.

 

[saw]

Hi, is the 12V fuse ok? Look at the diagram, its not enough that the relay is functioning in/out- it has got to deliver 12V to the plugs.

 

[Squash]

I'm not certain here, but often taking off the front tire and removing the skirting opens up a whole new world of accessibility.
Normally a deep 14mm socket does the trick.
Grab an extension as as noted above a universal.