I recently had a breakdown on my ‘74 XJ12 with a 6-liter swap. The fuel tank switch connection melted. Pics below.

Has anybody else had this problem or heard about it? My car (and thus this switch) was off the road for 30 years but since I’ve been working on it I’ve used the switch hundreds of times (testing and etc).

My set up is not stock and this switch is connected to a relay that connects to aftermarket high flow fuel pumps in the trunk. I’ve read that the original SU style pumps draw 3 amps or so and that modern fuel pumps draw similar amperage but I’m not an expert in fuel pump amp draw?

any thoughts or insights? This happened within a few miles of me changing the fuel system and adding a second pump in the trunk so that everything operated more like the original configuration. (But with relays versus the pumps and solenoid switch valves being directly wired). Coincidence?

 

It might not have anything to do with your pumps...especially since you've used a relay for them.

Those push-on connections at the switch are not the greatest set-up. They tend to loosen. Loose connection = high resistance = heat!

Cheers
DD

 

Agree with Doug, if the pumps are running through relays, pump current will not be going through the dash switch ...IF correctly wired. Verify what exactly is connected to the switch and how. The relays are a very low current draw on the switch and it sounds like you may have something mis-wired, or a potential short to ground with no fuse.