Fj60 fuel sending unit issues (1 Viewer)

[georgiacruiser87]

My fuel gauge was staying at empty since I’ve owned the truck. I decided to sneak a peek at the sending unit tonight to see what my problems were.

It looks relatively new so the previous owner must have replaced at some point. I bench tested the sending unit and get 20 ohms at empty and 120 at full. I then plugged in the sending unit and with some help moved the sender to the full extreme and the fuel gauge went to maybe a hair above 3/4. Then at empty it went down to empty. Easy enough.

I put everything back together and it’s reading less than a quarter so I’m confused.

I checked the connection from plug to sender that seems solid. I also just jumped the sender plug and it went up to past full.

Do I have a bad sender? Bad connection? Or just plain missing something. Thank you ahead of time.

 

[Spook50]

A little over three years ago my fuel pump quit (on Christmas Eve no less, on top of a hill that was solid ice. Good times). After getting my 62 towed back to my house (harrowing to say the least) and troubleshooting in a blizzard, I discovered that the wires that pass between the fuel tank and the body had been nicked and the fuel pump lead finally gave up. I'm wondering if a similar situation is happening for you and you're getting a lot of resistance in that run of wires. Regardless, you've got a LOT of resistance somewhere between the sender and its connection to the gauge that you'll have to find, and I suspect that section of wire is where it's at.

Something to try: get a multimeter, disconnect the sender and pull off the left side cargo panel. Just barely aft of the wheel well you'll see a four-wire bundle that passes through a rubber grommet on the body. Looking at the wires coming from the connector, you can match of the colors to the two wires on the end that connects to the fuel sender. Use your multimeter to check for any resistance between the two connectors. If you see any resistance, there's your problem.

Here's a link to the thread detailing my odyssey with this section of wire harness, starting with the point where I discovered the harness was the culprit: Bragging rights over. 3FE quit and won't restart - https://forum.ih8mud.com/threads/bragging-rights-over-3fe-quit-and-wont-restart.1272294/post-14223009

 

[georgiacruiser87]

A little over three years ago my fuel pump quit (on Christmas Eve no less, on top of a hill that was solid ice. Good times). After getting my 62 towed back to my house (harrowing to say the least) and troubleshooting in a blizzard, I discovered that the wires that pass between the fuel tank and the body had been nicked and the fuel pump lead finally gave up. I'm wondering if a similar situation is happening for you and you're getting a lot of resistance in that run of wires. Regardless, you've got a LOT of resistance somewhere between the sender and its connection to the gauge that you'll have to find, and I suspect that section of wire is where it's at.

Something to try: get a multimeter, disconnect the sender and pull off the left side cargo panel. Just barely aft of the wheel well you'll see a four-wire bundle that passes through a rubber grommet on the body. Looking at the wires coming from the connector, you can match of the colors to the two wires on the end that connects to the fuel sender. Use your multimeter to check for any resistance between the two connectors. If you see any resistance, there's your problem.

Here's a link to the thread detailing my odyssey with this section of wire harness, starting with the point where I discovered the harness was the culprit: Bragging rights over. 3FE quit and won't restart - https://forum.ih8mud.com/threads/bragging-rights-over-3fe-quit-and-wont-restart.1272294/post-14223009

Yeah it’s weird before I started working on it the gauge stayed like below empty. Possibly just moving the wires or taking the electrical connector on and off and now it’s sitting a little above empty. I’ll chase the wires back to the driver cargo area tonight and see if I can’t find any issues.

Clean and inspect the plug and if I have to continue to chase and inspect wires.

I don’t have my service manual in front of me but I’m assuming when it’s full it’s at 17 ohms and empty would be the 120 is that correct? That would fit as a frayed wire or semi bad connection would cause increased resistance.

 

[OSS]

When the sender is removed from the tank, you can easily actuate the arm up and down, (as you did) to see if it works on the gauge.
If it does - then there's nothing wrong with the wiring. Likely the float arm is sticking when the unit is installed in the tank. Exercise it to see if you can loosen it up a bit.

 

[georgiacruiser87]

When the sender is removed from the tank, you can easily actuate the arm up and down, (as you did) to see if it works on the gauge.
If it does - then there's nothing wrong with the wiring. Likely the float arm is sticking when the unit is installed in the tank. Exercise it to see if you can loosen it up a bit.

So with the sender out and plugged in, I did move the arm up and down. With the arm at “full” position the gas hand was right above 3/4. I could just be nitpicking at that point. I’ll move the sender up and down see why it’s catching or now moving.

Has anyone seen the actual float piece go bad? Just curious I feel like I’m throwing noodles at the wall hoping something sticks ha!

 

[georgiacruiser87]

I exercised the sender and it’s moving freely. Installed it back In the full tank of gas. (Testing outside the truck the sender at the max height was was 125 ohms.) the sender while installed only reads 62 ohms.

I’m getting a new sender and seeing if that fixes it.

The fuel gauge even at 62 ohms is still barely above empty. So we will see?