Are you doing a blowby test or compression test?. Irrespective of being diesel or petrol the plugs or injectors have to be removed. The simplest would be to remove the pump plug / fuse to prevent fuel spray. . For petrol nothing will fire with plugs out.
For blowby the engine needs to be warmed and the engine turned over by hand to tdc number one. Blowby test kit fitted. Engine backed up by +- 20mm before TDC then back to TDC and reading taken, Then TDC next firing cylinder, test kit fitted and so on.
The difference between the input pressure usually 90 psi and secondary pressure [ blow by] will tell you if you have a rings, or valve leak problem. For suspect valves sealing listen at the exhaust pipe you will hear a distinctive sound.
Hope this helps.
Thanks for the reply. Just done a basic dry/wet compression test & although readings are low they are constant so im happy. Ive got a cheapish gauge so again low readings. Car is now running as it should after renewal of inket manifold gasket. Something else will go soon after all its a Zed. Cheers.