7 replies to this topic

[Elwyn]

Hello

 

1993 L reg SPI Cooper, manual, RHD

 

I've either imagined it, or this has been raised and answered before (possibly a few times), but I can't find it through the search function.

 

Anyway....

 

Temp gauge works fine

Fuel gauge reads empty

The tank isn't empty

 

I've connected a jumper wire to the green / black wire on the sender unit and the -ve battery terminal

The gauge went up to full

 

I have a spare / new sender unit

Outside of the tank, in the boot, I then connected the green / black wire to the new sender unit

I connected the jumper wire to the black cable (not connected to the new sender unit) and the other end to the -ve battery terminal

I moved the float up and down

No change on the gauge

 

Now, I might have misunderstood this second test

I'm very good at misunderstanding

 

Do I need to connect both (green / black and all black) wires to the sender unit then also run the jumper wire from the black wire connection at the sender to the -ve battery terminal?

 

If I've performed the second test incorrectly then head back out to do it properly and the gauge still doesn't move (connected to a new sender), what then?

 

A fault in the black wire from boot to dashboard?

 

I have had the tank in and out of place a few times while I've been replacing the rear sub frame and rear shock absorber(s), so it's more than possible that I've damaged something in doing so.

 

Are there any other tests?

 

Regards

 

 

Elwyn

 

 

[Tornado99]

Apparently it can happen that the internal float arm gets hung up against the tank and prevents movement. Can you use a coat hanger wire or similar to fish around and tell if the flaot arm is free to move?
Otherwise, might be the wiring not correct or damaged or the floats sensor is faulty. First step is to find out why your spare unit has a problem.

[Elwyn]

The spare is new

Out of the box / tube

I'd hoped that I would test the new one before fitting it and fit the gauge going up and down as I manually move the arm

But no

Nothing

Suggests a wiring problem?

[Quinlan minor]

I may be missing something, here, but just connect the new sender exactly as the original was connected. Lift the float to the upper position, turn on the ignition and it should indicate 'Full'. Move float lever to bottom position and the guge should go down to 'Empty'.

If it does that, fit it. Job done!

[Elwyn]

I've tried the new sender

Connected it to the green / black and black cables that go to the gauge from the boot

Lifted the float up

Lowered the float down

Nothing on the gauge

Just as there's nothing on the gauge with the wires connected to the old / current sender in the tank

It's possible that my old / current sender is faulty AND by chance, the brand new sender is also faulty, but I doubt it

Edited by Elwyn, 15 August 2021 - 07:28 PM.

[Tornado99]

Put an Ohm meter on the new sender connections and try measuring change in reading as you move the float. If erratic or full open circuit or short circuit you have a bad sender. If it looks good then issue could be wiring to the dash has an issue.

[Elwyn]

Thanks

Very helpful

20 to 252 ohms

Increasing directly and smoothly in relation to the movement of the float

Black wire between the gauge and the sender is the fault, it seems

Unless I can find an obvious fault, would it be easier to run a new wire?
Coincidentally, the front seats and the carpet are out of the car

[Tornado99]

Good the hear it is not the sender. Did you test both new and older units?

I don't know how the existing wiring is run to dash. If. The problem line is buried in some kind of conduit with other wires all wrapped up, then running a new wire would seem the easiest path. Be sure to fully secure it if running underside of car and using a conduit covering (like the plastic corrugated or flexible mesh type) can be a good idea.

Can you test the suspect wire with the Ohmeter attached at each end (you'll need a long bit of good wire to make the connections)? Might be all but the connection points are fine and you just need to scrape the connectors free of corrosion. A wire bristle brush and or White Vingear to soak the terminals in for twenty min usually do a great job.