Briggs & Stratton 3.5HP - Trouble Starting

bigalxyz

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Hello forum,

I'm in the UK. I own a small Mountfield (don't know if that brand exists in the US) petrol mower with a 3.5HP Briggs & Stratton petrol engine.

About 2 weeks ago it developed a problem. The engine would start easily using the primer bulb but would then cut out a couple of seconds later. Assumed some kind of blockage in the carb meaning that fuel can't get through to the engine.

I dismantled the carburettor and gave it a thorough clean with some carb cleaner. I also cleaned out the fuel tank, re-oiled the foam air filter, etc.

Upon reassembling everything, the engine started on the first pull of the cord and ran fine. Problem solved, I thought, as I mowed the lawn with no trouble.

A few days later, unfortunately, the problem is back. Engine starts on the primer bulb but won't keep running after that.

Does anyone know what might be going on?

I don't know if it's relevant, but just to mention in passing: the gasket between the fuel tank and carb seems to be a little tatty and I had some trouble getting it to fit when I reassembled everything. Could this cause problems? I'm pretty sure everything else is in ok condition.

Can anyone advise please? It's quite an old mower, not worth much money, so if any repairs are likely to be complicated or expensive then I probably wouldn't bother - the time might have come for me to scrap this mower and get a new one. Not sure.

Thanks!
Alan.
 

ILENGINE

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I would change the carb diaphragm/gasket, because it also has a section that acts as a fuel pump to move the fuel from the bottom of the tank to the little well area under the carb.
 

bigalxyz

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Thank you. I'll try it. Easy to find the gasket/diaphragm on eBay here for pennies, worth trying I think - will place an order and see what happens...
 

bigalxyz

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Success! 10 minutes to fit diaphragm/gasket. Also got some clean fuel - the stuff I'd be using was a few months old, wonder if some water etc. had got in there. Anyway, running nicely now (FINGERS CROSSED!).

Thanks everyone.
 
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