S2 petrol only starts on starting fluid, then runs fine

Hi folks, I have an intriguing problem with my 1967 S2a. It wont start with any amount of cranking, but as soon as you try starting fluid it fires up fine, then runs sweetly. Subsequent starting is then a bit hit and miss - and if it does start it requires quite a bit of cranking. Same performance with air filter on or off. Have replaced carb, in-line fuel filter, fuel lines (new), and tank and I've reconditioned the fuel pump. I am still suspicious of the latter though as when I blow into the outlet (or suck on the inlet) a bit of air still passes. I tried a secondhand pump and that didn't result in any improvement (the pump worked fine on another s2 I had a few years ago, but to be fair, also fails the suck/blow test). Might still be pump? Could it be too rich mixture? Doesn't obviously seem to be blowing dark smoke. Compressions on all cylinders are 140.

Firstly STOP using "starting fluid" ! ( unless you want to do an engine rebuild ) - washes the oil of the bores and increases wear exponentially.

IME, a one way valve has failed, allowing fuel to run back to the tank overnight... might be a weak lift pump too, which needs the engine running to pump enough fuel..

I'm presuming you've checked the LP for being on cam, and having the correct spacers/gaskets etc...

If your LP is a proper one, which you can take apart and clean, then have a nosy at the poppet valves for bits of carp ... Not that long ago, I pulled a sliver of wood (!) out of a valve in an LP, which was producing similar symptoms

If I leave my s3 for a long time it struggles to start so I remove the air fliter from the carb and pour a bit of petrol.straight down its.throat. It starts ok then. Have.you removed the.plugs.and checked.their colour for.signs.of richness. Have.you fitted a.transparent fuel filter close to the carb? If so, can you see fuel in it. The pumps were good in the day but after 40-50 years not so good, the replacement pumps arent.great either. Consider fitting an electric pump.

Col

Have you checked the tank filter is not partly blocked

mystery said:

Have you checked the tank filter is not partly blocked

Click to expand...

Or the brass gauze in the union with the carb.

What colour are the plugs before you try to start? What do they look like after cranking and a no start?
What does the spark look like? Timing could be retarded

I'd be checking the fine guaze filter in the glass bowl of the lift pump as well had that blocked before...

Thought a bit more and re-read your post youv'e changed the whole fuel system...carb/pump/lines/tank yes? But did that include in-tank delivery pipe if so then the problem is something else...run a wire from battery to coil as under cranking starter sucks a lot of power and see if it makes a difference a weak spark under cranking with easy start which is more volatile could be why it fires worth a thought...

+1 on the above. Your issue is almost certainly spark. I suspect someone has fitted a ballast resistor, but the car still has a 12V coil. Change it for a 7V coil or remove the ballast resistor and all will be well.

On ignition what about the coil feed? some vehicle switch to only coil and starter when starting. A not infrequent fault is feed to coil which is off untill the key is released. any residual engine rotation will allow it to start.
the addition of a volatile into the cylinders, will ignite, then you release the key, coil is energised and normal running commences.
When hot, with oil less viscous, if you release the key during cranking and it starts.. a bugger to find. try taking a temporary lead from battery to coil. but don't leave it on for too long....

ciderman said:

On ignition what about the coil feed? some vehicle switch to only coil and starter when starting. A not infrequent fault is feed to coil which is off untill the key is released. any residual engine rotation will allow it to start.
the addition of a volatile into the cylinders, will ignite, then you release the key, coil is energised and normal running commences.
When hot, with oil less viscous, if you release the key during cranking and it starts.. a bugger to find. try taking a temporary lead from battery to coil. but don't leave it on for too long....

Click to expand...

Already suggesred that and yes disconect wire after trying...if it works run a wire from starter to coil...

any news?