Draining Old Fuel from Tank

[Carl Steven]

#12147

Hello All. I wasn’t to drain the OD fuel (petrol) from my 780 gas tank and remove and replace the pump and the filter bag attached to it. Any ideas on the safest and most effective way to drain the fuel from the tank? Should I just disconnect the hose where it attached to the main pump under the car and if I do, will it all drain out? No matter what I do I’ll try this first because I want to drain the fuel before it enters the main pump.

I had thought of disconnecting the wire connector to the tank pump where it comes into the trunk and, using a spare battery, connect the red wire and the ground wire to a loose battery. That should just activate the pump and pump all of the gas out. This wire lead has four wires associated with it. I believe two are related to the fuel guage and sending unit and I believe a red wire is for the pump and there is a black ground wire.

To run this car I need to have a clean and reliable fuel system but I loathe the thought of doing this job. I’ve seen some related videos on Youtube so I have an idea of how it’s done and what I’m getting in to. Any thoughts, ideas, or experiences to share?

Thanks,

Carl

[Johan Vlagsma]

#12148

Some time ago I replaced the float inside the fuel level sender. I didn’t drain the fuel, just took out the whole assembly and temporarily closed off the tank with plastic. It is a lousy job working in the boot through a small hatch and over a pool of petrol but it can be done. Make sure you do this outside or in a very well ventilated space. Be very careful not to stress the other hoses there eg the one going to the top of the tank for venting air to while filling. I had a fuel leak there while filling up and it took removing the rear axle to get that sorted.

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