Series 11a overheating

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?

Reply to
Duracell Bunny
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Polite (and serious) suggestion. The poor old upside down early series ignition coil has leaked some of it's oil out over the years and is overheating.

Expected (and non-serious) suggestion. I'll come and have a look at it for you - if I can't fix it I can probably take your mind off it. ;-)

Reply to
EMB

:)

as in austins thread about dissy's. I had trouble with a condensor on my car. It would only play up when it was hot - car wouldnt restart for 30 mins after stopping or would die when i got in a queue in town. worth checking if it looks really ancient like the one on my car did!

Reply to
Tom Woods

If it is poor (old) wiring and you don't fancy a rewire (which might be a good idea) maybe you could fit one of the early multiblade military fans to the waterpump? Just a thought, it might do the job *and* take the load off the wiring.

Martin

Reply to
Oily

On or around Fri, 16 Mar 2007 21:01:27 +1300, EMB enlightened us thusly:

bloody daft, that. never understood mounting it upside down.

Reply to
Austin Shackles

Brilliant. I shall use that.

Reply to
Rich B

Probably spot on, as usual EMB - the coil is one of the few original parts on the old thing. For that reason alone, it's worth changing ...

Heh - why, kind sir, you wouldn't be wanting to take advantage of a poor old widow, would you???? (don't answer, I know what the response will be ;) )

Reply to
Duracell Bunny

Do any series petrol engines start when hot? I've never come across one :) But I'll check the condensor. The distributor was rebuilt & re-timed when I converted the engine to unleaded some years ago.

Reply to
Duracell Bunny

When I fitted the Kenlowe, I did update the wiring, that's all on a heavy duty, relayed circuit. But there is a gremlin somewhere in the wiring, sometimes circuits fail to come on - only heavy circuits like horn (Klaxon A1) & Kenlowe fan. It never fails in the workshop with a meter in sight, needless to say.

Sometimes if the vehicle is pumping stationary for a while, I lift the bonnet - that always removes the overheating issues.

Reply to
Duracell Bunny

let the water run away after serious wading - else it runs into the HT cap.

Whenever I've swamped it when hot, just leaving the old thing alone to evaporate the water away from distributor & leads has done the trick. Bit embarrassing when it happens in town when you've just hit an almighty puddle, though! Which leads me to think the whole problem quite possibly is the coil

Reply to
Duracell Bunny

Thanks, gentlemen (and EMB) for a good selection of suggestions. I'll examine each of them.

Reply to
Duracell Bunny

Always happy to help a lady (or you).

Reply to
EMB

If that's what you want to read into my offer then so be it ;-)

Reply to
EMB

Touché :)

Reply to
Duracell Bunny

On or around Sat, 17 Mar 2007 13:22:48 +1000, Duracell Bunny enlightened us thusly:

Edward II normally does, when he's not throwing a wobbler.

Reply to
Austin Shackles

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