Hot starting

 
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leloups66
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Joined: 15 Oct 2016
Posts: 9
Location: RG26 5TU

PostPosted: Wed May 09, 2018 6:30 pm    Post subject: Hot starting Reply with quote
While I am on here I thought experts may be able to solve another issue for me. I have a 2.25 litre 1974 petrol engine. Starts first time every time except when it is hot.
I thoought fuel evaporation so i re-routed the fuel pipe.

I think maybe the timing is alittle bit out as even when it is not that hot I get the same issue.

Any suggestions?
Wrap the exhaust?
Insulate the fuel line?
Put an aluminium heat sheild around the carb

I can't be the only one this happens to.
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Alan Drover
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Joined: 31 Oct 2013
Posts: 1128
Location: North West Hampshire

PostPosted: Wed May 09, 2018 7:00 pm    Post subject: Reply with quote
Evening again leloups66.
My 2.5 engine has the same hot starting problem and at first I thought it was fuel vaporization but I noticed black smoke from the exhaust when it did start.
I have recently discovered the reason. The fuel in the float chamber expands with the heat from the exhaust manifold when a hot engine is switched off and the fuel overflows into the inlet manifold. Pressing the accelerator when restarting activates the accelerator pump which puts more fuel into the manifold. The answer would be an effective heat shield. I made one up and positioned it under the float chamber and held it in place with the carburettor mounting bolt but it was not very effective.
I think it's something we'll have to live with. It's the fault of the rubbish that passes for petrol these days.
This doesn't happen with my MG as it has full heatshields and SU carburettors don't have an accelerator pump. In addition the MG has a stainless steel exhaust manifold which is lagged thus keeping the radiated heat down but don't lag a cast iron exhaust manifold as it will crack.
_________________
Alan Drover.
1975 SWB hardtop with a 2.5 petrol engine, overdrive, front disc brakes, parabolic springs, hand throttle, Defender doors and Wolf wheels.
Also a 1977 Stage 2 MGB GT.
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