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MG MG Y Type - Petrol Guage Sender Unit

Neither the manual nor David Lawrence's book are specific enough to help with our problem. The dashboard petrol guages of Y saloons and tourers are different but I assume the sender units are the same. Our YT guage moves from empty when the ignition is off to full when it's switched on irrespective of the amount of fuel in the tank. I think the sender unit must be stuck in the "full" position inside the tank. has anyone got a quick fix suggestion without draining the tank and removing the unit for inspection?
Rob Dunsterville

Check the wiring from the sender to the dash - the dial is basically recording an open circuit. You either have a short (a break and a wire is shorting to ground) on the wiring possibly somewhere, a faulty gauge or a faulty sender by the sounds of it. To test the gauge use a bulb - if it lights up, it isnt the gauge. You can then do a similar test at the sender coming off the sender (not the feed to the sender but the feed to the gauge). A light at this stage would indicate a faulty sender I think.

Paul
Paul Barrow

Thanks Paul

I'll carry out your suggestions and report back but it may take a while as it's not top priority - just something that I need to fix. Rob
Rob Dunsterville

No guarantees on the test as I am no Auto-electrician but the principle is there!
Paul Barrow

I think that if you disconnect the wire at the sender unit and the guage still reads full, then you have a short in the wiring.If the gauge reads empty then you have a faulty sender.Also, I had to remove my tank recently and noticed tht the sender unit is mounted closer to the upper section of the tank so it can be removed when the level is low, (ie. without completely draining it.
Ken Cowan

The sender unit is a simple rheostat, you can check the guage by connecting up a spare from any older car, earth it, and waggle the arm up and down. Saves taking the current one out, and trying to re-seal it.

Neil.
Neil Cairns

Rob:

I'm experiencing the same issue on my YT, did you ever get to the bottom of this?
Mark Weissman

Good advice by Neil and Ken.

Paul
Paul Barrow

Good luck if you have to take out the sender unit! I had no luck gettting out the tiny bolts without breaking them. Anyone got some ideas? Don't suggest a bit of heat!!
Steve
Steve Brompton

Tons of patience, oudles of time, and gallons of penetrating oil such as Plusgas is where I;d suggest. Dont know if its available outside the UK but I think it is wonderful.
Paul Barrow

Proper penetrating oil has been unavailable for many years in Australia, and the aerosol can stuff is just cosmetic.

An old timer gave me this recipe 20 years ago, and I have used his brew to dismantle lots of Y's and other junk over the years.

Black Magic Penetrating Mix
75% - Diesel Fuel or Kerosine
20% - Metholated Spirits
5% - Light Machine oil (Sewing machine oil)

Best results are to give it at least an hour to soak in, and a sharp tap to the screw/bolt will assist in the mechanical penetration.

The screw threads in my Y fuel tank sender mounting are a mystery - not BSF, not BA, not UNF, not Metric, not Mad Metric, not BSW - does anyone know?.
Tony Slattery

Glad I stocked up on about 20 cans before I left the UK - Plusgas has never let me down, but the recipie above sounds excellent too.
Paul Barrow

Hi Guys

Found time at last to investigate the problem with your kind guidances. The guage tested OK. Power was reaching the sender unit OK so no faulty wiring which I'd expect and had hoped due to the rewiring 20 years ago. I put a wire connection onto the sender unit terminal with a bulb and earthed it. Wow the bulb lit up and the guage showed quarter full!!!

Seems that the sender unit is not earthing itself properly any more. I loosened and retightened five of the six screws holding the sender unit in place but that didn't recreate an earth. I presume the tank is the normal earthing through its monting on the chassis. As this is currently not effective I now plan to attach a new earth wire to one of the sender unit's six screws and earth it to the chassis. I shall use this earth also for the wiring of the rear flashing indicators that I will fit soon.

How does this sound? Appreciate any feedback.

Thanks

Rob
Rob Dunsterville

This thread was discussed between 14/05/2005 and 26/06/2005

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