Dash Failure - Any ideas??

[J6KFS]

Hi all,
 
My problem is a strange one......
 
just had a fresh engine re-build on my FD and when i set the ignition position to II the dash comes on fine with mileage, warning lights etc. etc.
 
upon actually starting the car the dash immidately goes out, no rev counter, speedo, mileage, warning lights etc. although the engine is idling fine-my power fc is giving me a rev counter reading, water temp etc. so i assume all my sensors are ok....
 
I have not yet installed a battery have jumped it from a boost pack to the pos and neg terminals and then left the leads on whilst it was running-could this be a problem?
 
any ideas are welcome at this point.
 
Cheers :Thumbs-up

[ashc]

yes, probably dodgy ground/earth

[FDAsh]

yes, probably dodgy ground/earth

Agreed....