Intermittent rev counter readings

[magoogriff]

Evening all
I have a rover v8 engined Fairthorpe Pathfinder kit car ( google it and if its yellow or yellow with a black stripe its mine ). According to the engine number its a 1985 engine. It runs on electronic ignition lucas coil. At idle the rev counter wont move and typically doesnt move until revs get up to 1500 or so, sometimes more sometimes not at all. Can anyone point me in the right direction as to why this might be?
Thanks

[DaveEFI]

Need more information being a kit car - as there are different ways to drive a rev counter over the years. So make and model might help. Have you got the installation instructions for the rev counter if an after market type?

[stevieturbo]

And has the rev counter ever worked correctly ?