I found out why Marge was cutting out suddenly - vacuum in the tank. Removing/replacing the cap sorted it every time this week and it happened quite often. It must be the warmer weather.
Now the odd thing is, it's an ornery-type, locking cap, and on dismantling it I find two tiny, spring-loaded ball-bearings, clearly intended to equalise pressure through the cap, - one facing each side.
I'd stripped & cleaned the cap before, and *thought* these airways were clear. They certainly move freely and there's no apparent obstruction to the tubes. This time I took a Dremel to the casting, to make bigger grooves and ensure free airflow.
It should work. I'll find out tomorrow. If it doesn't, is this a problem anyone else has had recently, and how did you solve it? I'm reluctant to make pinholes elsewhere, as diesel 'creeps' messily, and anywhere under the rear wing would block up pretty fast in the winter. I also intend to check the system for airlocks downstream, just in case changing the tank earlier in the year caused problems.
All thoughts appreciated, as ever.
Regards,
Simonm.