Pretty much the title sums up my problem. If I start the M2 on the bench then it is fine but as soon as it goes in the car it wont start

To take things a little futher (I suspected the IGN was the issue) I used an inverter to power a 12v supply in the car & used the existing IGN wire with no problems!

The 12v for the M2 comes directly from the battery & has a good earth but won't start my M2!

Has anyone any ideas?