IGNITION ISSUE

I REALLY need to stop ignoring my own advice. If a running problem on a petrol Land Rover appears to be fuel-related, it’s normally an ignition problem. But when I took the Lightweight from last month’s column for MOT and found that it was barely drivable, the symptoms pointed to a faulty carburettor and I spent a few hours dismantling, cleaning and fiddling with it before the penny dropped.

The problem was that if I lifted off the accelerator and then gently applied power again the engine would momentarily die before picking up. There was also a light tapping noise under load which sounded mechanical in nature, and which I had assumed was unrelated to the cutting out. The cause of both faults? A faulty vacuum advance unit on the distributor. What was happening was that when the throttle was opened, even a small drop in manifold vacuum caused the timing to move so far that the engine would momentarily cut out. The tapping noise was pinking caused by the incorrect timing. I dug around in some boxes and found a Lucas 45D distributor with an electronic ignition module (which didn’t work), a Ducellier with a Lumenition conversion (which didn’t work either) and finally an old Lucas 25D from a Series IIA, on which the engine absolutely purred. An old lesson re-learned...