[Baffler]

I think there are some thin wires going under the pump. I'll take a look at those with a mirror or something.

If the engine dies immediately when you turn off the key the stop solenoid is working fine. I was originally thinking that if you had corrosion in the wiring loom that it may have been receiving a poor signal from the ignition.

Yeah, I gave the solenoid some power on the bench and it made a click. But it wasn't quite as I expected. Like it might have been sticking. And there was a tiny amount of fuel under the rubber cap like the body was leaking.

Does it work just ON/OFF? I'll test it more, when I get those appropriate o-rings.

I imagine the fuel under the rubber cap has seeped past those o-rings you replaced and collected over time. It may even be getting past the plunger and escaping through windings.

Not sure how much travel you should see/hear on the solenoid but like all these things it should be of a clean action...if you know what I mean

But I think something happened already after I put those new o-rings. Haven't driven much after that, but I think it starts and runs better. The problem with the occasional lack of power at low RPM still persists. After what I've read, these could all be symptoms of a bad advance solenoid.

I'd say it's been doing it warm and cold, starting and driving. Just randomly. Sometimes it lasts a few seconds, sometimes a minute. But maybe it happens most often, when stopping to traffic lights and such.

Interestingly, your symptoms sound very similar to those written about in this UKDieselParts blog.