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MG TD TF 1500 - wire gauge

since I have no knowledge about the specifics of wiring and current I could use a little help with my initial engine start up. What gauge wire should I use to power the coil and the fuel pump from the battery?

Rob
Rob Welborne

I'm not an expert, more of a seat of the pants guy.
Wire gauge becomes most important in charging circuits, to insure enough amperage to charge the battery, lighting circuits which require heavier gauge wire to carry the load of lights, and of course the high amperage draw of the starter motor.

I am guessing from your question that you are connecting things with temporary wires for your start-up.

That said, most any auto parts store wire 18 gauge or heavier will sufficiently power the coil, the fuel pump uses a tad more amperage, I'd go 16 or larger there for your temporary connections. Otherwise (if the engine is in the car) you could just use the wiring in your original or replacement harness.

It goes without question that the cables from battery to starter will need to be standard heavy gauge battery cables. Any lighter and they will just heat up upon attempting to turn the engine over with the starter.

In automotive circuits, heavier than needed wire causes no problem (they're just bulkier and more costly), but lighter than needed will slow things down and heat them up.

Best of luck; just be careful, double check your connections, so as to not let the smoke out.
Bob;
RwB Brown

I believe that the factory used a 7 strand wire for ignition and fuel pump, which translates to 18 AWG. I like to error on the heavy side and always use 16 AWG (if ordering from British Wiring, that would be 14 strand wire). Cheers - Dave
David DuBois

probably not your problem but here's where many people get messed up - wire gauge relates to the wire's amperage capacity not to the power it can deliver to a device. 14 gauge wire will carry 15 amps regardless of the voltage. But power (the requirement of the device being served) is volts times amps so that 14 gauge wire carring say 10 amps comfortably at 110 volts can serve a device needing 1,100 watts (nominally 1 kw). In our cars (and in just about all cars) the voltage is not 110 but is 12 (about a tenth) so you can power a 100 watt light bulb on your house circuit (about 1 amp) with skinny wire (maybe 20 or even 22 gauge lamp cord). To power a 100 watt headlamp in a car using 12 volts needs about 9 amps so you need at least 16 gauge or even 14 gauge wire to handle the amperage. Then there's voltage drop through skinny wires and inductive/dynamic resistence (none of which I fully understand0 so figure what wattage you're serving, calcalculate the required gauge based in the amps and go up one size.

Jud
J K Chapin

I used 14 gauge for most wiring and 12 gauge for the heavy loads such as headlamps and feed to ignition switch.

I also used the NASA specified non flammable wire (after the capsule fire)
that is teflon insulated and fibreglass sheathed.
It won't burn up when you try to let the smoke out, it keeps the smoke in and blows fuses instead.

anyhow, 24, and 18 gauge are far too light for many of the currents carried in our T Car 12V systems
Don Harmer

This thread was discussed between 10/04/2013 and 11/04/2013

MG TD TF 1500 index

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