Technical Mk3b 1.3 Multijet intermittently wont crank

[howardgt]

Dear all, I've got a 54 plate 1.3 Diesel Multijet Punto, and I'm looking for some advice.
95% of the time the car will start perfectly fine, however intermittently it won't start (usually when the engine is hot - petrol stations etc).
The starter motor does not crank, though strangely there is a voltage drop when attempting to start (the heater fan slows and the lights dim etc), but for some reason the starter motor won't fire.

Any ideas please as this is getting quite frustrating and always seems to do this at the most awkward times... usually at petrol stations or on car ferries!

Usually when this happens it will crank after approx 10 attempts, but sometimes I've had to leave for 10mins before trying again.

I've owned the car for almost 5 years and it has done this very occasionally for years, but now seems a lot more common.

Any ideas appreciated!

 

[AndyRKett]

check the large earth wires between the engine/gearbox and the car body, i had a similar problem about a year or so ago, turned out to be a corroded earth wire had broken so that the engine and as a result the starter motor were no longer earthed, started intermittently and got progressively worse.