81 FJ43 new fuel gauge now only shows maxed out

[Nolacajun75]

Hello all, hope someone could help me out here. I have a 1981 fj43 non-us model from Columbia, so no smog, no emissions with a 2f engine. Runs great.

I removed my gauge cluster and upon inspection noticed there was a voltage regulator transistor thingy on the back which broke a wire when I pulled it out. Then my fuel indication system stopped working. I was advised that this was a fixed to the voltage regulator not working in the fuel gauge to just get a new fuel gauge or replace external voltage regulator which I went with the gauge.

So after talking to some people I was advised to remove the voltage regulator on the back all together and just replace it with a new fuel gauge. Now it does not work. Once you put the key in it maxes out to full.

Is there supposed to be in a wire going directly from the sending unit to the back nut on the instrument cluster of the gauge or is it internal through the circuit board.

I'm confused because it works perfectly fine before the wire broke, Just proposing the gauge and it will be it but nope. Hopefully someone can clear this up. I did try running a jumper between the two posts on the back of the instrument cluster where the voltage regulator was going to just to see if it would fix the problem but it did not and not sure why the wire was going to. The fuel pressure will make a difference but somehow did.

Not sure why it worked fine before and now it's doing this can someone help me out?

 

[Nolacajun75]

Oh one more thing. The little spot that's raised right behind where the fuel gauge mates up to the circuit board. It has a metal tab sticking out of the gauge itself that touches the circuit board surface. I was told this supposed to be grounded and the part where the tab touches was painted. So when I installed the new gauge I roughed it up to make it a metallic surface so it would have a ground. That is the only thing I did differently. I'm going to cover it up to see if it makes a difference and get rid of that ground.

 

[45Dougal]

Oh one more thing. The little spot that's raised right behind where the fuel gauge mates up to the circuit board. It has a metal tab sticking out of the gauge itself that touches the circuit board surface. I was told this supposed to be grounded and the part where the tab touches was painted. So when I installed the new gauge I roughed it up to make it a metallic surface so it would have a ground. That is the only thing I did differently. I'm going to cover it up to see if it makes a difference and get rid of that ground.

You've done the right thing. The tab is a ground.
It's working perfectly ( flashing).

 

[45Dougal]

Oh one more thing. The little spot that's raised right behind where the fuel gauge mates up to the circuit board. It has a metal tab sticking out of the gauge itself that touches the circuit board surface. I was told this supposed to be grounded and the part where the tab touches was painted. So when I installed the new gauge I roughed it up to make it a metallic surface so it would have a ground. That is the only thing I did differently. I'm going to cover it up to see if it makes a difference and get rid of that ground.

You've done the right thing. The tab is a ground.
It's working perfectly ( flashing).

 

[Nolacajun75]

Okay but the fuel gauge is not working. I use this picture to test the back of the gauge cluster with a light. All checks are good except pin 4 that goes to the fuel. Sender does not glow in blink so I guess there's no voltage there on the back of the post shown is where I measured.

Like I said it worked fine before I changed the gauge out so not sure what's going on.

Also, if I go to pin 4 to ground on the round plug detached from the gauge I get nothing in it as well.

One more question, what is correct? I have a 81 fj40 electrical wiring diagram and I had this picture I got from this forum showing the colors of the wires and where they go to on the back of the barrel connector going to the instrument cluster. My wire colors match up to the wiring diagram, not the picture but the picture says 3rd and 4th generation so I thought it should be the same.

 

[Nolacajun75]

Hello, is there anybody out there!

Lol

Well I checked the ground from the sending unit and it is good. The wire from the sending unit has continuity to the connector under the battery compartment and also all the way to pin number 5 the yellow and red wire. Thought it should have continuity to pin number four but not sure now as it worked perfectly fine before with the regulator installed now with the new gauge and not working. Is not adding up

Here's a picture of the plug I am talking about.

 

[45Dougal]

You can see on the circuit board where the copper tracks run. These connect the gauges to the circular connector. Just follow the track.
The one that says IGN is the 12v feed from the ignition switch.
This links to the fuel gauge as I've shown below.
The fuel gauge then creates 7v which it uses internally, and also shares with the temperature gauge (green line).
The other pin on the gauge goes to the sender.
The fuel gauge sender wire should be yellow/red (2 across from the 12v wire).
Maybe your connector got turned around a bit?
Remember that you're looking at the mirror image when you look into the female half of the connector.

The title of the thread says its stuck in full. Is this still the case?

 

[45Dougal]

Let's see a photo with the round connector in place - maybe clean your wires with some wd40 first if the colours are hard to see.
Also check that each socket pin is snug around the male pin - the female part can get very loose over time

 

[Nolacajun75]

You can see on the circuit board where the copper tracks run. These connect the gauges to the circular connector. Just follow the track.
The one that says IGN is the 12v feed from the ignition switch.
This links to the fuel gauge as I've shown below.
The fuel gauge then creates 7v which it uses internally, and also shares with the temperature gauge (green line).
The other pin on the gauge goes to the sender.
The fuel gauge sender wire should be yellow/red (2 across from the 12v wire).
Maybe your connector got turned around a bit?
Remember that you're looking at the mirror image when you look into the female half of the connector.

The title of the thread says its stuck in full. Is this still the case?

View attachment 3669450

Thank you. I will report back. Now my Temp gauge is working fine. Not sure what I must have cleaned to get that to work and now my fuel gauge just sits at empty. It was maxing out to full before I took everything apart and cleaned it. I also found that my sending unit is completely incorrect. It has two starter connections on top of it with a pigtail which no Land cruisers ever came with so not sure what it is so I ordered a new one from cruiser corps. Checked the sending unit and it was grounded on both terminals so I'm taking it. That is not correct. Check the ground in the wire. Going to the dash and it is good

 

[Nolacajun75]

Let's see a photo with the round connector in place - maybe clean your wires with some wd40 first if the colours are hard to see.
Also check that each socket pin is snug around the male pin - the female part can get very loose over time

Roger that, thank you. I appreciate it. I will get a picture. I'm not able to for a couple weeks as the Coast Guard sent me out of town for work. Soon as I get back I'll reply back and let you know what's going on and hopefully I'll have my new sending unit and PCB for the gauge to install at the same time as well.