Golf Mk5 GT TDi 170 Cranks and Eventually Starts

[heyescroft]

Apologies as I know the www is littered with questions like this and they all seem to have various solutions.

Last year my car suddenly decided it would only start if I cranked it for some time, it would lose power, run rough but error codes was suggesting that it may be injector problems and VCDS suggested that there was possible problems with the injector loom and added to this I had some wiring issues, the result of a small fire when a mouse decided to nest in the sound damping blanket under the bonnet and the material fell down onto the exhaust manifold and smoldered.

To cut a long story I replaced the injector loom and repaired the damaged cables but the engine wouldn't start, not even if I jumped it. A couple of months ago after the weather improved I recharged the battery but left it disconnected and after a few days I decided to try starting it again and found that the battery had lost most of it's charge. I had a spare battery lying around which I tried but this time it tried to start, so I put a jumper on and bingo the car eventually started, clouds of white smoke but the engine ticked over and run smoothly for over an hour, it responded to the throttle and it seems to run well. Can't take it for a spin as it's SORNed and uninsured.

Now the HOWEVER - when left over night it's back to it's I don't want to start but now eventually starts without the aid of a jump. It's parked on level ground and I've read that it could be the fuel lift pump, Cam/Crank sensor, EGR valve flap or even the starter motor. The fuel filter has only had a couple of months use but as once the engine is running it is smooth and responsive I'm banking on it being the fuel pump rather than one of the others as I haven't seen errors relating to sensors or glow plugs. I have a friend in the local scrap yard so would a pump from any VAG group diesel work or is there a specific pump for this vehicle, as a pensioner I can't afford to waste a small fortune on a pump to find that it isn't the problem. I have a small coolant leak but the level dropped even when the car was just sat idle for a couple of months so again I'm banking on it being a small leak somewhere rather than a head gasket or such like, there doesn't appear to be any exhaust gas getting into the coolant.

MTIA Any other suggestions welcome.

[Crasher]

The BMN is an awful engine cursed by the most unreliable injectors I have ever encountered but all modern engines are very sensitive to low voltage. Have you been able to get a comprehensive code read carried out?