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MG MGB GT V8 Factory Originals Technical - amp load cooling fans and fuel pump

i am nearing completetion of the 5.0 ford EFI conversion in my 1978 MGB. i hope to use the original wires to power my A/M fan (1) 10Amp draw and my EFI pump draws 5.5 Amps. does anyone know the amp draw of the 2 OEM fan motors and the amp draw of the SU fuel pump? i anticipate using a relay and trigger it from the original fuel pump wire to run the fuel pump and fuse it at the battery due to the short run. of course i will use the Ford OEM upset switch also. hope to have it done in time to motor to Terre Haute in June.
kelly stevenson

Kelly. I am using the stock wiring to run my 2 8" puller fans mounted on the rad.

For the fuel pumps I have the stock carb pump running off the normal wiring. I ran one new feeder wire from the battery to a relay, the relay is triggered by the hot wire for the stock pump.
Larry Embrey

From my measurements the OE fans draw about 10 amps, although with 30 years of bad connections and the small gauge earth wire the factory used it can be significantly less than that, with accompanying loss in performance. I've taken the unused output from the alternator to the relay (which the V8 had but the 4-cylinder with identical fans didn't), and put a local ground for each fan under its mounting bracket, in addition to the original ground wire so it helps the headlamps as well. Seeing as the original source of 12v for the fans was from the green circuit, which also powered the heated rear window, brake lights, reversing lights and turn signals, I don't think you need worry about the gauge of the wiring.
Paul Hunt

thanks for info and your replys. the fuel pump wire will act as a trigger for the relay. it appears that the wire to the fans are adequate qauge to carry the current.the additional earth (ground) is an excellent idea and will be incorporated. i have to add an additonal earth from the battery to the front of the car for the ECM direct earth. i have noticed improved performance in other accessories when the earths were cleaned and re-connected.
kelly stevenson

I'm running two roller vane fuel pumps off the standard wiring, A feeder and a high pressure pump.
They have a fuse of their own.
Must be more than a year now and no problems at all.

This thread was discussed between 27/03/2005 and 30/03/2005

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