As an additional follow-up, tried some starter fluid into the intake with the new relay and the engine fired. Only runs long enough to use up the starter fluid. Tried both resetting and jumping the inertia switch yet again: didn't run. Jumped the pump and it hums nicely and there's pressure in the fuel rail if I check the valve,but won't start with the pumped jumped and running. So spark, no fuel.
Fred, I would like to help, perhaps my 2 cents are completely useless, but perhaps it is good to check all possibilities.
I'm not familiar with the Plus8 engine, but I'm very familiar with the kind of symptom (which can be caused by many reasons of course). If your engine fires up using starter fluid but soon afterwards dies, I had the same symptom with a Porsche 928S from 1983. The culprit was the "Temp sensor II" which tells the system to enrich the fuel mix for cold start. We had looked for more than months before we found the reason for the fault.
May be the Rover engine also uses such kind of temp sensor which is responsible for cold start fuel enrichment? At least the smptoms with the 928 were exactly the same, only running with starter fluid as long the temp sensor 2 was broken.
