Some sort of fuelling issue on a longer test-drive today. Car was running fine, accelerating well and driving nicely but then died at one point. I think it happened twice, both times going over 3500rpm in fourth, the engine seemed to falter and stutter and then eventually die. The first time this happened, I pulled over to check the bodged fuel lines, but no issue and no leaks under the car. When I turned on the ignition, however, it wasn't clear if there was fuel running into the filter or not, but it definately didn't have that half-ful appearrance that I would expect. This issue repeated a little later, after the car had started up and run with no issues after the first problem, but I was able to cruise a bit and then bump start back into normal driving.
It seems likely to be a fuel starvation issue - which would explain the stuttering and misfiring - which may have a number of causes:
1. The new fuel pump doesn't provide enough fuel. This will be easy to test but unplugging it and measuring its flow rate... It also seems unlikely, given it was brand new and sold to me by an MG parts specialist!
2. Some of the new lines are blocked, narrow. Though why this would only cause issues sometimes I am not sure.
3. Perhaps most likely, some bad fuel or a bit of air passing through which causes temporary starvation. Not sure how to check this, or solve it? Perhaps just add in more, good, high-octane petrol?