P100 Weber Carb Idle Jet Cut-Off Solenoid

[James England]

Hi All

I just joined FOC and posted on the introductions part of the forum. I thought I would post here something which may help others.

My newly acquired P100 pickup was fine when I bought it a few weeks ago. Then it developed a very rough idle and would not run at low revs without the choke being slightly on. Next day, it suddenly ran fine, then a few days later, rough idle again. Then it was fine again! Finally, it would not run at tickover at all.

I removed the Weber ICT/ICH carb and disassembled it completely and throughly cleaned everything. I checked the idle jet cutoff solenoid and it clicked fine. I put the carb back on the engine and all was fine.....until the next evening. Same problem again.

After much self-doubt and thinking an oil and filter change I'd done was somehow affecting the engine, (that's how desperate I was ... 2+2= 22), I checked the oil level and there was no possibility that I'd overfilled it. I removed the carb again and removed the solenoid, then took off the idle jet from the end of it. The needle was in the extended/ closed position. It moved painfully slowly when current was applied to it, then stuck open when current was switched off. I put it back in the carb and ran the engine...after two minutes, the tickover problem returned. I removed the solenoid and it was in the extended/closed position and stayed there when current was applied. It had inched back out again from the retracted position and finally blocked off the idle jet. Things we becoming clearer! As a final test, I cut off the end of the needle with snips and the engine ran absolutely fine for two days with no sign of the problem returning.

Today I fitted a new solenoid cutoff assembly, listened to the healthy click and the needle retracting every time. Problem completely solved!

A lesson I learned here was that rushing to eBay in a panic (its a work vehicle) in order to buy a brand-new carb at £150 would have been daft and a waste of money. I nearly did exactly that.

I found out that these carbs are fitted to loads of vehicles and the solenoid is to cut off the fuel when the key is turned off, mainly so that air cooled engines especially, or water cooled with a carbon hot spot, don't 'run on' by sucking fuel through the idle jet. No doubt obvious to many members but not to me at the time.

So, if anyone gets a similar problem....head for that solenoid firs of all!

[jeebowhite]

Excellent advice, and thanks for joining and sharing!