Hi all,
It's midsummer here, air temps around 38°C daytime. I use my ancient series 2.25 for spraying a bit, which means trundling round the paddocks in 1st low while I murder the weeds using a pump driven by the rear PTO. Rad temp is controlled by the original engine fan, assisted by a Kenlowe when necessary.
After a while, it starts misfiring, probably due to fuel vapourising in the carb before it's got through to the manifold. The problem is that to use the PTO correctly I'm running at a slowish tickover (say 800 rpm), so a decent misfire means an engine stall. The Kenlowe is currently set to cut in at an indicated temp of 90°C, and it's at this point that misfires seem to start.
I'm wondering how to sort this, is it the engine temp soaring that's causing the misfire, or the Kenlowe's whopping electrical load.
Alternator has the smallest pulley I could get my hands on, to maximise output at tickover speeds, but ammeter is still reading a little negative.
Running on the road on these hot days is not an issue at all, it's just when I'm driving really slowly when there's no real air flow through the engine bay that this happens. If I happen to be in the cab when it starts misfiring, I can sort it by disengaging the PTO & revving the engine a few seconds (the rear PTO drive shaft is too long to cope with speeds over 1000 rpm). Setting the RPM a little faster also helps, but the overheating stage happens a lot faster of course.
Radiator was re-cored recently & the block was descaled, so it's not a cooling system problem.
Any (polite, please, EMB) suggestions?