Fuel Pump and Overdrive Fusing

Damage to the V8 rear harness inside the boot. The fact damage is visible here shows the short must have occurred either in the pump or closer to it than this point. Damage runs all the way back through the rear harness and into the main harness, through that back to the ignition switch, and from there on the brown down to the solenoid. This has happened to both my roadster and V8 before my ownership. The roadster is still using the original wire so presumably wasn't damaged too badly, the V8 has had a new wire run in (brown, the blue is a wire I added for the rear fog lights). It also shows why fuses must be as near to the supply as possible. If there had been a fuse near the pump then it would have prevented the damage from this short in the pump, but if the short had happened in the rear harness under the car the fuse wouldn't have blown and the same damage would have occurred in the rest of the wiring.

The bullet connector near the RHD pedal cover where the two white wires from the main harness join the white wire to the rear harness and the pump. Note the heat damage to the pump wire on the left of the connector, insert the pump fuse between this wire and the 4-way connector. On 77 and later the white wires from the main harness are white/brown, also there is a fourth wire - also white/brown - which goes into the gearbox harness for the overdrive circuit. You can take both the output wires into a new 4-way bullet connector and insert a fuse between the two 4-ways, but if one circuit blows the fuse it will stop the other working. Better to use one fuse for each. North American spec cars are wired differently as they have an inertia switch in the pump circuit, and the OD wiring is different, see the main text. (Image by David Farrar on the MGOC Forum)

V8 Pump and Overdrive fuses: They should be installed as close as possible to the supply where a unique wire can be accessed. I've inserted them at existing spade and bullet connections which avoids cutting into wiring. It is also reversible - should anyone want to! I had to put the V8 overdrive fuse in the engine compartment as that was the first place I could use existing connectors as it has the manual switch on the column stalk with a multi-way plug connecting to the main harness. On the roadster with the manual switch on the dash I have put the fuse on the back of the switch using spade connectors instead of bullets. When I had a major overflow from one of the V8 carbs the close proximity of the two allowed me to cross-connect them so I could use the overdrive switch to turn the fuel pump on and off!