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MG MGA - fuel tank grounding

I'm back! Still having problems reading fuel level. At least got it so it reads "full" even when empty now. I have verified a good ground to the gauge but wondering how to ground the tank? I've run a ground to one of the screws on the sending unit and to the pipe leading from the tank but neither corrects the problem. So should I drill a small hole in the flange of the tank itself and attach a ground there? I see no other ways to attach a ground to the tank itself. THis is really frustrating me after 2 years of effort, simpleton that I am. thank you.
danny jacob

If the gauge is toast, it reads full when the tank is empty. Just to encourage you....

The tank is grounded anyway through the fuel lines, which should be metal and are fixed to the chassis with metal clips.
dominic clancy

I hope not... 1st thing, had it rebuilt by nossiger!!! but would a failed sending unit cause it to peg?
danny jacob

Hi
Make sure it is grounded. Just take a piece of wire and attach it to one sensor screw, then directly to chassis. The gauge have to have good ground too. If you have enough wire, run it from fuel tank to gauge. If all else fails, go to Barny site, there is all about, and more, you want to know about fuel gauge.
Martin
Martin

Danny, have you removed the sending unit & test it? Also look a www.mgaguru.com I found a used tank unit and did the transplant. The wire in the sending unit was broken.
Cliff(SC)
Jones

Danny, you must go to Barney's MGAGURU site. There is plenty to read and I recommend that you do everything
possible before you start taking the sender unit out of the tank. Also go back into the archives. Even just recently there has been stuff about gauges and sender units. Do NOT take it for granted that the tank is earthing correctly through the fuel pipe. Try taking an earth from one of the sender unit mounting screws directly on to the chassis - you should find a fixing point very close to the sender unit.
D C GRAHAME

Danny.
The tank reading full when empty. I had a friend that had put the sending unit in the tank up side down.
Took us quite a while to find it.
Jim.
Jim Jensen

Among my long list of things to sort out now that my restoration is almost done is the fuel guage. Mine reads just below half when full and full when empty.

I've driven the car almost 10,000 miles in the last 18 months with this "inconvenience", but I would like to tackle the problem again


Danny - what does your guage read when full?

- Ken
Ken Doris

Ken, - This sounds like you may have an MGB sender unit in your MGA tank. The MGA unit ranges from 70 ohms full to 0 ohms empty. The MGB unit is something like 200 ohms empty and maybe 30 ohms full, and never goes to zero ohms. This can make your MGA gauge work backward and never go to the empty mark.
Barney Gaylord

I have evidence that the two previous owners of my "A" had fuel gauge problems...
Yes I found the sender upside down. Right way up it worked just fine. The connection terminal should be at the bottom. Agree with everybody else.
Just my two penneth...
Pete
Pete Tipping

Just cleaning up my tank and sender as part of the restoration; the outer plate on the sender says TOP at the top. Bob Prentice
rsa prentice

As for the grounding of the fuel tank,mine has a small rectangle tab welded to the passenger side lower outside edge of the tank.It has a hole in it for screw connections and this is where my ground wire attaches. To the best of my knowledge this is orgional.Should there not be some concern regarding attaching the ground wire to the screw of the fuel sender unit. The screw protrudes into the acutal inside of the tank and touches gasoline ,when the tank is full. If some one were to incorrectly MISS WIRE the ground and cause it to be live would that not be an immediate fire or explosion of the gas tank? Please understand I am not an electrical genius, so I maybe wrong in this regard but is it just athought. Gordon
Gordon Harrison

It would be almost impossible to mis-wire in a dangerous manner. All you are doing is running a wire from the sender screw to the nearest convenient spot. The tab 6 inches away that secures the wire harness to the frame would be the closest workable point.
Even if you did mess up and ran a hot wire (from Where?) and grounded it to a sender mount screw all you would do is melt the wire.
R J Brown

I asked on the 4th post has he tested the unit, with no responce all he has said is that he had it rebuilt (great) but has he tested the unit? No-one can help you if you do not respond to a post.
Jones

RJ
As I said I am not an electical wizz but do not discount that someone could miss wire the tank. Heck in home reno's I have found regular white extention cords buried into a groove in the plasterboard and connected directly to 14 guage house wire with only electrical tape. Thanks for the explanation Gordon.
Gordon Harrison

Sorry I did not respond to an earlier question about my sending unit fuel gauge problems. Ive been distracted: the weather is great here in the NC foothills, my car is otherwise driving the best since Ive owned it for the last 10 years so Ive been out enjoying it. Friday it refused to start so after a few hours of amateurish fooling around I discovered the electrical connector leading to the fuel pump had slipped loose today Im just proud to have survived a Lucas experience and fixed a problem myself without being stranded along the road!

No, I have not tested the rebuilt gauge. In fact I disconnected the green/black wire at the sending unit yesterday and the gauge still pegs. So I just disconnected the gauge completely, plan to monitor my driving distances, fill up frequently, and since it does no harm, just continue to drive it until I have more patience and a better understanding of the advice Im seeing here. Thanks to all.
danny jacob

This thread was discussed between 22/04/2007 and 28/04/2007

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This thread is from the archive. The Live MG MGA BBS is active now.