[TonyS9]

If you are losing the rev counter (going to 0), and the engine is still turning (say its in gear and slowing down), then you definately have an igntion problem. The rev counter is driven by the back emf from the coil (output driven by ignition amp). The rev counter will work provided the engine is turning, it only needs the crank position for input (via the ignition ECU and amp).

There are 2 common(ish) proiblems

1. crank sensor (CPS)
2. Amp failure on high temps (ignition amplifier)

If you are still getting fuel during the fail condition (from the pop) then it seems the CPS is still working (the fuel ecu would cut the pump if there is no 5v signal from the ignition ECU). If you could connect a light to the fuel pump power then that would confirm it if you see it still lit during fail condition. I have often said a fuel pump power indicator would massively help diagnose these types of problem.

I would therefore go for the ignition amp at this point.

There can be other problems of course, like the coil, but that is more likely to be a complete failure, and these coils are very reliable.

FYI the fuel pump relay can fail in other ways than the solder joints, it does seem a bit underrated for the job and gets too hot. Always carry a spare.