Sub tank gauge not working

[Macgyver 1hz]

Hi there
I have recently purchased a 100/105 series cruiser (not sure of the difference yet) it has the one gauge for main and sub tank but when I switch over to the sub tank the gauge shows empty and the fuel light comes on but the sub tank is full. The gauge works fine on the main tank so it's not the gauge. Are there any common problems that anyone knows about and can I test the sender unit without pulling it out to eliminate that problem and start checking connections and wiring any advice would be great

 

[Baromy]

Hi there
I have recently purchased a 100/105 series cruiser (not sure of the difference yet) it has the one gauge for main and sub tank but when I switch over to the sub tank the gauge shows empty and the fuel light comes on but the sub tank is full. The gauge works fine on the main tank so it's not the gauge. Are there any common problems that anyone knows about and can I test the sender unit without pulling it out to eliminate that problem and start checking connections and wiring any advice would be great

Thank you Macgyver. I refer to your problem with the sub tank switch. I have "exactly" the same problem which occurred to me only two days ago. When I switch to the sub tank it goes directly to empty and the light comes on. I filled the sub tank earlier in the day so I know I had plenty of fuel. I spoke to my mechanic today and he could not solve the problem so I was just wondering if you have had any success in fixing your switch. My Cruiser is a 2001 model, 4.2 T/D. If by any chance I do come upon a solution I will send it to you immediately. Many thanks baromy

 

[chapel gate]

Im familiar with the 80s sub tank set up but not the 100 series but surely
Its the sender unit?

On the 80 diesel the sender has two wires, a earth and signal wire to the gauge. So if its not working there are 3 options, wire broke, sender not working, gauge not working.
You gauge works, so your left with two options..

looking at the wiring diagram in your fsm will break it down.

 

[Baromy]

Im familiar with the 80s sub tank set up but not the 100 series but surely
Its the sender unit?

On the 80 diesel the sender has two wires, a earth and signal wire to the gauge. So if its not working there are 3 options, wire broke, sender not working, gauge not working.
You gauge works, so your left with two options..

looking at the wiring diagram in your fsm will break it down.

Thank you "chapel gate" for your prompt reply. I will investigate the sender as you suggest. Sounds like it might be the problem. Many thanks.