MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - TF Fuel Pump

MY TF pos grd
Moss price for their solid state neg grd pump 207.95
Price for the pos grd is 159.95

Is there any problem with buying the pos grd and reversing the wires ??
Bill
mgbill

Why reverse the wires if your TF pos grd?

If your TF neg grd answer is yes.
Willem
Willem van der Veer

<I>>>Is there any problem with buying the pos grd and reversing the wires ??
Bill </I>

Yes!! Big problem. Don't do it!!

Either buy a pump with the proper polarity, or open up the case and reverse the diode, or get someone to rebuild your old pump.

Having a fuel pump with the case at a different potential than ground would be dangerous. You might be able to temporarily isolate the case from ground, but eventually, something will short it to the frame. Remember, the TF pump is up under the frame near the back wheel. The best possible outcome would be that eventually you would burn out the wiring harness. The worst possible outcome--well you can imagine that. You don't want to burn up your nice car to save a few bucks on a pump.
Mark B

You might be able to reverse the wires if the device is, for example, designed for negative ground and you have positive ground, but this could also get you in VERY BIG TROUBLE. Remember, the chassis is the return electrical path to the battery. Many electrical devices in a car make an electical connection of the device enclosure with the internal return electrical path. If you reverse the polarity in the wires that connect to such a device you will create a short circuit with a likely very bad outcome.

There are ways you can rework a device to accomplish what you describe, but it is not possible in all situations and you really need to know what you are doing.

Larry
Larry Shoer

Bill - The prices you are quoting are for the all electronic SU fuel pumps and there is no way you can reverse the polarity external of the pump without causing an extremely dangerous condition. Changing the polarity of these pumps is more complex than just reversing a diode, it requires a bit of delicate soldering on a circuit board that can be very easily damage if not done right. You might want to check with some of the people in this country who can repair the existing pumps (if you still have the old pump). See the SU fuel pump articles on my web site http://homepages.donobi.net/sufuelpumps/ for a list of people who do this work. Cheers - Dave
David DuBois

I agree with all the comments above but there is a safe way to do it. You have to find a polarity converter and put it between the harness and the pump. These devices convert positive ground to negative ground.Also the reverse. Used to be Radio Shack sold them to put transistorized radio's in positive ground cars. They give completely safe and reliable performance for just the situation you are inquiring about. Where one could be obtained today is of course a problem but somebody must have them.

There is another method too, buy from Burlin the kit to convert a fuel pump to electronic, just be sure that you buy the kit for the polarity you intend to use then never change. I'm sure Dave DuBois could rebuild your pump and install the kit. The remaining question is the economics of situation. It may turn out to be cheaper to pay Burlin their $200 plus than do any of these alternates.

My experience is that with the fuel pump mounted in the rear away from the heat of the engine that the regular SU point set-up lasts a very long time.

Cheers,

Bob
R. K. (Bob) Jeffers

Use an SU pump with points, then polarity won't matter.
Carl Floyd

I was buying a part on the SU/ Burlen website recently and I noticed that they now sell an electronic conversion module that allows you to eliminate the points in a non-electronic fuel pump. I think it was around 40 pounds. So if anyone has a pump with points and you want to convert it to an 'genuine' SU electronic, that is all you would need. It is a kit. I think I would replace the diaphram at that point also.

I have been running with a SU electronic, positive ground pump for 2 years with no problems.

Larry
L Ayres

This thread was discussed on 22/02/2008

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.