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MG MG Y Type - Fuel Gauge Problems

Can Someone Please Give me Some Ideas of What Could be the Problem With my Fuel Gauge. It is Always Stuck on the Full Position Regardless of how Much Fuel is in the Car.
I have Been Told it Could be the Fuel Sender Unit. But not Being a Whis wuth Electrics, any ideas Would be a Help.
Regards Phil.
Phil Ramsden

The sender is a "variable earth". If the tank is full, the "earth" is 100% and your gauge with show full.

So either the sender is broken, OR the wires from the sender leading to the gauge is making contact with the body, creating a 100% earth.

You might try to find a working sender from any car an try that before you start messing around with the properly sealed sender on your car.
Willem van der Veer

I forgot to ask if the gauge returns to zero if the ignition is off?
Willem van der Veer

FuelGauge has a coil type and a bimetal type.
Y-type is a coil type.
Sender is a 100-ohm type.
Full at 100 ohms. Empty is 0 ohm .

When it assumes that meter and Sender are normal.

FuelGauge is always a full display.
--- Disconnection or loose connection----

Fuel Gauge is always a middle display.
---Lever adherence of Sennder.

I linked the picture. Please refer to it.

http://roppatu.hp.infoseek.co.jp/cgi-bin/img-box/img20070507221321.jpg
XPAG Masaaki Sakaguchi

If you need to replace the sender, the fuel tank will need to be drained off (drain plug conveniently placed centre and bottom front edge of tank) and tank removed.

Removal of the tank, and refitting is fiddly but can be achieved using axle stands clearance - I recently did a friends YT this way.

When you have removed the tank be very careful about undoing the old screw bolts as they may have seized in the tank. Use penetrating oil and soak. It is all too easy to snap the heads off!

Once you have the old gauge off if the tank is extensively rusted inside you will benefit from sealing the tank - Moss Motors do a three stage sealing kit (part numbers 220-620, 220-630 and 220-450) and it is easy to apply if you follow the instructions.

Replacement fuel senders are also avaialble from many sources as they are the same as MG Magnette and MGA ones.

However Phil, check the easy things first though like the wiring connection at the current sender (may just be touching the side of the tank, or a stray connection along the line of the wire up to and including the fuel gauge behind the dash.

Good luck.

Paul
Paul Barrow

I too am experiencing a problem with the fuel gauge sticking on full. My problem occures only when the fuel tank is filled to the top. Once fuel is consumed the needle remains stuck at full. The needle stays on full even after the ignition is turned off. A sharp thump on the dash panel will release the needle and then the gauge works fine untill the next fill-up. Would I be right to assume that the problem is not an electrical one, but of a mechanical nature within the gauge and if so can anyone recommend a fix.

Terry
Terry Ciantar

Firstly Hi to Terry. Pity you didn't raise your problem within my hearing at the Maitland Meet otherwise we could have had a chat! I have had guage/sender unit problems which I have fixed. I think your problem is with the guage on the dash board and the only fix will be to remove it and take it to an instrument repairer as the needle needs lubrication. You could try yourself with a good squirt of WD40 if you can remove the instrument from its housing.

Secondly Hi to Phil and sorry I have not logged on for a while to assist. If you have eliminated the causes of the problem as electrical then the problem is probably that the float arm of the sender unit is stuck in the upper or "full" position ie it is recording full on the guage. As Paul recommends removal of the sender unit is the objective. It is possible to remove it without removing the petrol tank. Remove the rear wheel and you will have access to the six hex headed bolts. Soak with a penetrating oil or similar overnight. Then see if you can loosen each of them gently just a little and in rotation. You may have to use a screw driver due to space restrictions as the bolt heads are slotted. If you can loosen them all then drain the tank and continue to remove them and you should be able to withdraw the sender unit. If you destroy the bolt heads due to excessive force and slippage of the tools as I did then you have no alternative and you have to remove the tank. The workshop manual says you have to remove the exhaust pipe first but as mine was rusted solidly in place I had no alternative but to jiggle and jaggle until it came out! With the tank on the workshop bench removing the stubborn bolts is easier with more elbow room. I found the sender unit arm was stuck in the upper position due to corrosion and penetrating oil eased it into full flexibity. I purchased two new gaskets (second one for the inspection plate in the centre) and six new bolts from a Sydney MG parts supplier and after reassembly the guage has been accurate on the dash board which is a relief and comfort. The T Register's Totally T Type magazine has articles on helping fix leaks if the sender unit doesn't make a tight seal on reassembly. Luckily mine did. One last point. The bolts are excessively long but the replacements are shorter. If the sender unit has been above petrol level for a long time the long threads protroding into the tank will now be rusty. Mine were. Thus withdrawing them through the tapped retaining ring welded on the side of the tank is hazardous. The best way is to undo a bolt just a little until it becomes tight then back off and ease to left and right then unscrew a little more and so on. Patience is needed! If you break off the head of the bolt as I did with two of them you have to employ the multi grips, more penetrating oil and hope they'll see you through! If you need further help please email me. Good Luck Rob
Dunsterville

Thanks for the advice Rob. I will be removing the instrument cluster from the dash and have a go at some lubrication. I have had a look at a spare fuel gauge which I have (rough) and it would appear to be a relatively simple matter to get inside and give it a spray. Re Maitland, I think we were all to busy having a good time to worry about minor problems. What a wonderful weekend.

Terry
Terry Ciantar

I'd be very careful not to use too much oil in instruments. If everything is coated in oil, dust will gather and cause problems later in the fine parts.

In a book I read about instrument restoration the advise was to dip a toothpick in light machine oil and use that to distribute the oil to strategic places.
Willem van der Veer

I would like to say thanks to you all for all your input to my fuel gauge problem, it appears it is the sender unit. Kind Regards Phil.
phil ramsden

Rob

WD40 is not a good lubricant. It is designed to displace water. Willem's recommendation of a very small amount of light machine oil is a good one. Another is to use something like LPS-1 which is a spray on lubricant which promptly dries. Also great on lock assemblies.

FWIW

Larry
49 YT
Larry Hallanger

Larry - Thanks for the input and recommendation. I was of the understanding that WD40 was all purpose but I shall be more cautious in its use in future! Cheers Rob
Rob Dunsterville

Is there a particular voltage that needs to be passed through the sender? My multimeter has a 1.5volt AA battery and is currently reading open circuit on a new sender whether the arm is in the "UP" and full position or "DOWN" and empty position.

Or do I have a faulty sender?

Paul
Paul Barrow

Paul

The sender is a sliding contact on a multiple wire coil. Resistance varies with the number of turns in the circuit. If it reads open circuit you have an "open circuit" somewhere.

HTH

Larry
Larry Hallanger

The sticking sender I attributed to zink leeching out from the sender casting and jamming the float shaft. This happened to my YA way back in the 70s. On the YA you do not need to remove the tank since the assembly can be accessed by removing the rear nearside wheel. Syphon the fuel as much as possible through the filler cap [ warning ] do not remove the plug from under the tank until the contents have been syphoned off! [ you dont need to anyway ] If you do all hell breaks loose with petrol everywhere. Please remember that an empty fuel tank is a potential bomb! The holding screws if they prove recalcitrant should not be forced [ they will break off and then need to be drilled out with a hand drill with grease on the bit tip to stop sparking ] A trick is with the aid of penetrating oil slightly tighten clockwise and then antclockwise keep rocking to and fro, it usually works. Remove the 3 screws from the inspection plate and work in some cycle oil around the shaft to free it up, I then completely filled the chamber with engine oil and re fitted the cover. dont worry about oil on electrical contacts it will stop oxidation between the contacts [ this is not CMOS or even TTL technology ] The proof of the pudding is that my sender is stll working.
Bryan Mellem

This thread was discussed between 19/04/2007 and 20/06/2007

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