Have made minor progress in finding the reason but not the answer to the problem. In my case it happens because I have put a DC2 interior wiring harness into my eg civic when I did the engine conversion.. and the dc2 wiring harness has an extra wire which the civic doesnt have.. it is a light green/red wire and its the "door adjar wire".

If I ground this wire, the interior light stays on permanently, if I don't ground this wire then wen the interior light is on the middle setting, the fuel pump wont turn off