Gas Gauge and Horn Issue in a 79 FJ40 (1 Viewer)

[79NCFJ40]

I have a 79 FJ40. The gas gauge only displays from 1/4 to 3/4 so I'm not sure how much gas is actually in the tank. The horn has never worked either. I've checked the fuse and cleaned the horn contacts under the hood. I've read the posts on gas gauge issues and they all talk about the gas gauge reading empty, nothing in between. They also mention it relates to other electrical issues. Is the horn malfunction related to my gas gauge problem? Some gas gauge posts talk about a ground issue. I don't think I have a ground issue if the needle moves. Any thoughts? Thanks.

 

[jarhead3121]

I'm waiting to get my FJ delivered, but I know it's gas and temp gauges in the cluster do not work. Could be the leveler inside the tank is shot? I will be testing the gauge when mine gets in by hooking the sender on the tank side to a test light. Seems pretty straight forward, and I found another post on here where a guy bought a socket and test light just for this purpose. Hook the other side to ground and should be able to see if it's the gauge or not. That's half the battle.

 

[Solace in Solitude]

I don’t know ‘79... but the horn is probably like my ‘78.

First, is your horn any good? Run a jumper,-pair, from the battery+ and battery-, to the appropriate connections on the horn. If it doesn’t work, it’s likely the horn itself.

If it works, via the jumpers, remove the negative jumper. If the horn still works, via the positive jump, make sure your horn has a good ground. e.g. Clean/scuff the horn ground... probably grounded through it’s mount.

Edit: if the horn works, via jumper, and doesn’t, via the horn button/ring, See if your rag-joint has a good ground wire.

If the rag-joint is good, pull whatever you need to pull, on the steering wheel, to access the horn button/ring and make sure the plus and minus connections are good.

‘79 has the fuel tank under the truck... if it has the same style fuel send as my ‘78, it has a thin shaft (float arm) to the float. If the float arm is bent, the readings will be wrong. If the sender is improperly oriented, the tank sides, or something may be interfering with the float.

As I understand it, the ‘79 fuel gauge and sender expect 120 ohms empty and 17 ohms full... just like my ‘78.

You can pull your sender (probably have to drop your tank) and test the ohms values, using a multimeter and simply moving the float arm.

Another thought: The gauge and sender are paired... the oem gauge expects the sender to send the same ohms range that the gauge expects (120-17 ohms). If you pull the sender, make sure its the proper sender... not aftermarket. Here’s what a ‘79 sender looks like: For TOYOTA Land Cruiser FJ40 1979-84 Fuel Gauge Sending Unit | eBay

 

[jarhead3121]

This is one of the threads I've been pouring over whilst awaiting my girls arrival.. Clusters, Gauges, Speedo & Odo meters

 

[jarhead3121]

This is the other with the guys test light info.. Oil Pressure Reciever and Sender Gauge - FSM test bulb

 

[3_puppies]

there is an access door in the floor to get to the sender in the tank, I'm thinking it is under the rear heater??

 

[79NCFJ40]

I'm waiting to get my FJ delivered, but I know it's gas and temp gauges in the cluster do not work. Could be the leveler inside the tank is shot? I will be testing the gauge when mine gets in by hooking the sender on the tank side to a test light. Seems pretty straight forward, and I found another post on here where a guy bought a socket and test light just for this purpose. Hook the other side to ground and should be able to see if it's the gauge or not. That's half the battle.

I'll give that a try, thank you.

 

[79NCFJ40]

I don’t know ‘79... but the horn is probably like my ‘78.

First, is your horn any good? Run a jumper,-pair, from the battery+ and battery-, to the appropriate connections on the horn. If it doesn’t work, it’s likely the horn itself.

If it works, via the jumpers, remove the negative jumper. If the horn still works, via the positive jump, make sure your horn has a good ground. e.g. Clean/scuff the horn ground... probably grounded through it’s mount.

Edit: if the horn works, via jumper, and doesn’t, via the horn button/ring, See if your rag-joint has a good ground wire.

If the rag-joint is good, pull whatever you need to pull, on the steering wheel, to access the horn button/ring and make sure the plus and minus connections are good.

‘79 has the fuel tank under the truck... if it has the same style fuel send as my ‘78, it has a thin shaft (float arm) to the float. If the float arm is bent, the readings will be wrong. If the sender is improperly oriented, the tank sides, or something may be interfering with the float.

As I understand it, the ‘79 fuel gauge and sender expect 120 ohms empty and 17 ohms full... just like my ‘78.

You can pull your sender (probably have to drop your tank) and test the ohms values, using a multimeter and simply moving the float arm.

Another thought: The gauge and sender are paired... the oem gauge expects the sender to send the same ohms range that the gauge expects (120-17 ohms). If you pull the sender, make sure its the proper sender... not aftermarket. Here’s what a ‘79 sender looks like: For TOYOTA Land Cruiser FJ40 1979-84 Fuel Gauge Sending Unit | eBay

Thank you. This is very informative. Question though, where are the ground wires on the rag joint? There are no wires on or near the rag joint on this vehicle.

 

[79NCFJ40]

there is an access door in the floor to get to the sender in the tank, I'm thinking it is under the rear heater??

Thank you., Yes. I have access to the top of the gas tank behind the front seat.

 

[Solace in Solitude]

Thank you. This is very informative. Question though, where are the ground wires on the rag joint? There are no wires on or near the rag joint on this vehicle.

Here’s the rag-joint, offered by cruisercorps, you can see the ground in the picture and read about it in the “tech tip“, under “Details”.

Steering Coupler / Rag Joint FJ40, FJ45, BJ 1972-1984

FJ40 Land Cruiser Steering Coupler Rag Joint

cruisercorps.com