Hi I have a rover engine from a 1995 420. It has been running very well until recently . For a while it had been running rich due to the ECU vacuum tube not being on. It ran fine for a while after replacing and had done well over 300 miles after this.

It then wouldn't start and isolated this to a bad coil which has since been replaced. I have also replaced fuel pump, fuel filter, air temperature sensor (comes up with a fault but won't clear), HT leads, king lead, dizzy and rotor arm along with spark plugs.

The fuel pump won't activate on start up but if I put a 12 volt supply to the fuel pump it will start but as soon as it gets warm it will just stop itself or will stop if any load is applied.

I'm pulling my hair out as to why it's not working properly

Could it be that tne fuel pump is faulty?

I've just spent months trying to sort a fault on a Saab 900 that would run fine when cold but slowly developed a misfire then died when it got up to temperature. It turned out that the new rotor arm I had fitted was faulty so don't trust that just because you've fitted a new part that it's good.

It sounds like the fuel pump has an issue delivering enough pressure. From what I understand you've bypassed the relay and fed it 12v directly? I've put a cheap fuel pressure gauge on the Saab while I was trying to trace my fault, I think I was about £20 including the t piece and fittings.

I've had rotor arms fail when hot, despite being fine when cold. It's worth trying another

Well I have replaced the lambda sensor and that seems to have fixed the problem. The problem was it was over fuelling and flooding the engine

Fingers crossed

My only issue now is an issue with the internal air temperature sensor. I know its working as it has been tested and the wiring is correct but the Mems 1.6 cant clear the fault code so it is stuck at 42 degrees