So the engine is fine, but oil pressure has dropped to zero on the gauge. I'm presuming its the sender? Or maybe a connection on the instrument cluster?
Where would you start with this?

 

Ground the sensor wire, see if the gauge fully deflects. If it does, it's probably the sender. If it doesn't it's likely the gauge, the cluster circuit ribbon or the sender wiring.

Paul

 

Thanks Paul,

Just pulled out the IC and found one of the multi plug connectors (the one on the right, behind the oil pressure gauge) just 'dropped off' the back. Didn't have time to reconnect and see if this is the culprit but I'll get back to it tomorrow.

 

So reconnected the plug and still no joy with the oil pressure. I then grounded the feed to the gauge and it came to life with full deflection, so its not the gauge. I found the oil sender and the oil pressure switch down on the left hand side of the oil filter. So I presume its a simple bolt out and bolt in the new sender?