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MG TD TF 1500 - TF Fuel Pump Wires

My new wiring schematic shows a Grey wire to the pump as the hot wire, is grey in the schematic representing a White wire? I have an electronic pump and don't want to damage it. PJ

Oh yeah, it's a new harness also!
Paul S Jennings

Probably the gray wire is correct, as I can't think of any other wire in the standard T-type harness that uses gray wire.
However, you will not damage the pump IF the polarity of the pump matches the polarity of the car. The color of the wire will not affect the operation of the pump.
Regardless, I always recommend that when doing the initial wiring and testing you leave the battery disconnected and use a battery trickle charger which has a circuit breaker connected in place of the battery. That way you will get enough power to test everything except the starter and not risk burning up the wiring harness or components. If you have something wired incorrectly, you will simply trip the circuit breaker or the component (lights, horn, turn signals, fuel pump, etc.) will not work.
Lew Palmer

Thanks Lew, That's what I'll do. I have a couple 1 amp and 2 amp chargers, plus I always double check the wires with an ohm meter from one end to the other to make sure I have the same wire. The circuit is as original, positive earth and so is the pump. Thanks again. PJ
Paul S Jennings

You will have two wires going to the pump Paul. One white (hot) and one black (ground).
MG LaVerne

Paul - I don't know where you go your harness, but the correct wire color to the pump is white. That said, Lew's answer is probably just as good - whoever made up the harness used gray instead (maybe they ran out of white). I would probably check the polarity of the voltage at then end of that wire before connecting it to the pump just as a precaution. A reverse polarity will not hurt the pump (but why take a chance with the all electronic pump). Cheers - Dave
D W DuBois

Dave, the wire is white in the harness, it's grey in the wiring diagram I have. As white won't show up in the drawing, they chose grey to represent it. I didn't know at first. Thanks to the more knowledgeable, Were cooking! PJ
Paul S Jennings

Paul, a 1 or 2 amp charger will be mostly OK, but I would prefer to see you use something that trips at around 10 amps. A 2 amp charger may be OK for most things, but will almost certainly trip if you test the horn, as that usually draws around 6 amps.
Lew Palmer

Thanks Lew, I have other chargers. I have one that trips at 8 amps which I'll use. My roll around can drop down to 10 amps, but goes up in stages of 20, 40 etc. PJ
Paul S Jennings

A white wire equals ignition switch controlled un fused. The white becomes green when ignition switch controlled fused. Despite what people say there was logic to Lucas in the 50s.


Jan T
J Targosz

"Despite what people say there was logic to Lucas in the 50s."
Right on Jan. Clear up through 1980, brown is primary 12 volts, unswitched and unfused. White is 12 volts switched and unfused. Green is 12 volts switched and fused. Purple is fused and unswitched. White/black is coil to distributor. I can look at the wiring of the TD or the MGB and tell exactly what wires go where. Since I am on the wrong side of the Atlantic, I don't know what the wiring did after 1980. Cheers - Dave
D W DuBois

This thread was discussed between 21/11/2014 and 23/11/2014

MG TD TF 1500 index

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