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MG Midget and Sprite Technical - fuel tank sender.

hi,in the next day or 2 im going to be dropping the petrol tank out and changing the sender unit (midget 1500), has anyone got any tips on doing it or is an easy job to do? thanks roy
roy judd

1) run the tank dry, or nearly dry, before you start.

2) clean the threads as well as possible before you try and loosen any of the 6 (7?) retaining nuts underneath, and the fuel pipes. In fact, soak them several days in advance to try and get them off to a good start (rust, paint over spray, mud, etc.). You can replace broken studs and rusted fuel / vapor line that twists into a mess when the nut is frozen to the pipe, but all of that is a pain, and ideally, enough lube over enough days will help prevent those things from happening.

3) start by removing the battery positive terminal under the hood (wouldn't do for a spark, from this point on)

4) remove the filler pipe inside the boot and cover the exposed tank flange sticking up in the bottom of the boot with some cellophane sheet (plastic wrap) and rubber bands to keep the fumes in.

5) remove the fuel outlet pipe and the vapor outlet pipes from the tank. Be prepared for the nuts to be frozen to the pipes and twisting the pipes into scrap, but you might get lucky. If you can, stick rubber plugs into/onto each of the holes so there's no leakage of fumes/fluid during handling in the next step.

6) finally, remove the 6 (or 7?) retaining nuts that hold the tank to the boot floor, and drop the tank.

7) remove the sender by rotating its retaining ring 1/4 turn (hit it with a screwdriver). Be prepared to replace the rubber sealing ring with the sender. Take care with the new sender as the power terminal is attached inside with a thin piece of wire and won't tolerate any twisting of it. It is a real good idea to test the new sender (move the tank well away from your work area, re-attach the battery and attach the sender to the wire and see how the gage reads when you stroke the float up/down). Do NOT bend the float arm. If you want to adjust the "full" or "empty", use the screws on the back of the gage to do that.

8) at this point, find out if the boot floor or the tank are badly rusted on the top and decide how to clean it up / repaint the damage (typical). Coat this area with a good dose of waxoyl or equivalent before installing the new tank. Use a new seal gasket around the filler neck and the boot floor, and new "rub strips" between the tank top surface and the boot floor before you put the tank back on.

9) re-assy is the reverse. Your actual mileage may vary. Product may have settled during shipping. etc.


Norm
Norm Kerr

thanks norm. il let you know how i get on. roy.
roy judd

basically agree with everything norm said above. few wee extras though. the 'rubbing strips' can rather neatly be fashioned from an old bicycle inner tube. Ask your local shop as they'll have loads they're chucking out. cut into strips & bob's you uncle. def replace the rubbed seal between the sender and the tank. Also plan to replace the big retaining ring - mine had 2 out of the 3 bits you smack with the screwdriver had been sheared off over time. not expense.
get loads of paint onto the top of the tank and especially the well where the sender sits, after only a year we had acquired rather a lot of rust up there. wonder if filling that area with grease might be a good idea, others will advise.

I assume you're replacing the sensor because it doesn't work? Have you checked that the gauge & its cabling are all good first? There's a connection in the drivers side rear wing for the fuel sender. earth it and your fuel gauge should SLOWLY start to creep up. if it doesn't then it might not be your sender but the gauge or the cabling. apologies if you've already ruled that out.

And be awfully careul with the tank & its fumes!! sounds silly but a mate who is very experienced in working on old cars blew him & his Capri up when fuel vapour was set alight by the heat of a halogen work lamp! He's fine but his Capri is no longer. So seal both the filler inlet and any other outlets & then put the whole tank as far away as you can, and not out in the sun!!

-Craig
C Robertson

thanks craig. iv got a new ring and seal when i got the new sender,it was an extra £2.50. iv replaced the gauge and it didnt work.iv tried just about everything so as a last resort i thought id change the sender.when i earthed it it did slowly go up so im hoping it i the sender.
roy judd

The sender seal I purchased turned out to be slightly larger than the old seal. I didn't realise this until after I dropped the tank to investigate the leak. When I get chance I'm sending the tank seal back.
Daniel Thirteen-Twelve

A suggestion I picked up in the past which worked well for me is a nifty mod to the trunk floor.

Cut a circular hole in the floor above where the sender goes on the tank. Fashion a circle of ally plate larger than the hole you've cut. The plate can be screwed down with a couple of self tapping screws and a make shift seal (I used a strip of draught excluder rubber) around the edge of the plate.

If at anytime you want to adjust the sender or replace it in the future you just need to remove the screws and remove the plate.

A very handy mod indeed!
James Ballard

I recently changed my tank and sender. The fitting on the fuel line where it screws to the tank is now seeping a little fuel. Should I use some kind of sealant (such as the yellow paint on teflon stuff)?

I discovered that it appears that I have a short somewhere in the wiring that goes to my sender (short to ground). When I turn on the ignition it the gauge pegs to full (regardless of how much fuel there is).

This is why I changed my tank (see attachment).
Rebecca


R Harvey

You'll be lucky if the new sender works for more than a month or so . . . . . . . . . . . . . . . . . . . . . . . . . . . grr . . . . . . . . . . mphm . . . . . . . . .
Nick

I put in a new sensor last summer. Its quality appeared slightly inferior to existing, but went with it anyway as current one was 125K+ miles.

It failed with the float becoming porous - which is usual.

Did consider just a float swap and use old sender...

Used the tyre inner tube idea outlined in thread (son used to be GB x-country mountain bike champ, so we have a good supply of tubes - we'd never use a repaired tube on his race-bike.)

Haven't calibrated it - seems OK; I always know when the fuel's low as the car hesitates on sustained accel, esp uphill and on RG bends.

A
Anthony Cutler

BALLS AR$E AND BO11OCKS, spent half the day yestaday taking out the tank and chamging the sender for a new one and it still dont work. iv tried 2 gauges and checked they both work with a 9v battery across the termanels. so it ant that, the temp gauge works fine so it ant the voltage stableizer and i even tried running a new wire from the tank to the gauge. HELP! any ideas anyone?? im tempted to go and partake in abit of banging my head on the wall.
roy judd

Roy

Tank needs to be earthed... normally achieved though the 6? bolts that keep it in place... might be worth a check

A
Anthony Cutler

That's why I have the nifty access hatch! have you tried the sender/gauge with a multi-meter? If both are ok... then ar$e indeed :(
James Ballard

This thread was discussed between 11/04/2010 and 16/04/2010

MG Midget and Sprite Technical index

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