Cold start Yes - Hot start No! Asdvice sought please.

[Doris53]

This continues to frustrate...!

I have rechecked the ignition system. Oddly I did find that the insulator on teh contact breaker terminal post was in teh wrong position, yet it has been starting as explained in firts post. I now have the lead from teh condensor and points on below the plastic insulator. There is an insulator at the bottom of the points 'spring'. So, according to the diagram I have this is now correct. Anyway, I have proved the ignition system and I have a spark at each plug.

Something that does happen everytime I have a failed start, is that when I pull the plugs, 2, 3, and 4 will be wet. As far as I can tell with my poor sense of smell it is fuel. No 1 will be dry but sooty.

So my theory now is that the plugs are immediately getting wet preventing the spark from actually firing the engine.

I have tightened the inlet manifold.

I have carried out a compression test on a cold engine: all cyclinders are equal give or take 1 or 2 PSI. All read 100 PSI (7Bar).

So, if I am on the right track, what is causing the plugs to immediately wet when I crank the engine? Is this a carb problem or do I need to lift the head (hoping to avoid this!).

Steve

[kevin s]

Might be worth trying a compression test when hot, also have you set the hot mixture? if it's way to rich it may be flooding out, if you can't get the hot mixture right there's a good chance the carb jet is worn.

[Doris53]

Hi Kevin

I cannot do anything with the engine hot at the moment as it does not start at all now! Just wet plugs no start. As a starting point with mixture I have wound the jet nut in fully, then out 12 flats. I have seen this reference point in other forum posts. I guess the carb jet could be worn. Is there a good way to check this or just by replacement?

[daveejhitchins]

Just in case . . . I had a 'similar' issue with a Hillman Imp which turned out to be a loose cork sender gasket in the fuel tank. Started OK ran OK but then would stop for no apparent reason. The cork gasket was being sucked down over the fuel outlet. Vacuum slowly dissipated - gasket floated away and we were off again.

Dave H.

[kevin s]

The hole in the jet gets larger with wear, it also might not appear to be round anymore.

Try leaving the plugs out for 24 hours, if there is a build up of carbon it could be holding a lot of fuel.

For the couple of hours it takes it might be worth pulling the head off cleaning it all up and re-grinding the valve seats.

One other thought, have you checked the valve clearances, to tight and there will be no compression when hot.

[Bill_qaz]

To confirm your theory of plugs getting wet and preventing restarting. Get 4 spare good plugs, when the engine refuses to start change plugs and try starting, if it fires up then it's plugs getting wet, if it still does not start then the wet plugs are a consequence not a cause.

[Doris53]

Hi all that are still interested!

Having done some more investigation I am sure I have a carb problem. I removed the carb form the manifold and there was a small pool of fuel sitting in the manifold inlet. I dried it all out (manifold, plugs, cyclinders) and replace dplugs. Then I cranked the engine withou the carb attached and the plugs remained dry.

So now to isolate the problem with the carb. I have checked the float shut-off valve and it is fine so I don't believe it is the float chamber overflowing. I have stripped the carb previously to clean it up and change necessary seals etc. However, I did not change the jet needle. Could it be this? Whatever it is it puts way too much fuel through on start-up. I'm not convinced (though could of course be wrong!) that a rich mixture would cause this extreme a problem?

Regards
Steve

[oliver90owner]

I have stripped the carb previously to clean it up and change necessary seals etc.

Was this, by any chance, immediately before this problem arose?

[jaekl]

Make sure the vent on the fuel bowl is open. If it's closed, the bowl will become pressurized and push fuel into the carb.

[Doris53]

Make sure the vent on the fuel bowl is open. If it's closed, the bowl will become pressurized and push fuel into the carb.

I cannot see a vent on the fuel bowl on my H1 carb - is there one? If so where?

Today I have re-checked the float bowl fork is correct setting (9.5mmm bar) when it shuts the needle valve. I have also checked the float (brass) does not have any holes in it.

[panky]

If you look where the float chamber outlet is there should be what looks like a small metal clip set against the carb body, this is the cover for the vent/overflow. It is a simple hole drilled in the casting.

[Doris53]

If you look where the float chamber outlet is there should be what looks like a small metal clip set against the carb body, this is the cover for the vent/overflow. It is a simple hole drilled in the casting.

Sorry but I still cannot find it. I have just looked.

[panky]

This is for a bigger SU but it should be similar on your carb. You can see the 'clip' at the base of the brass outlet connection in this listing

https://www.ebay.ie/itm/255532995022?ha ... R7S_64XyYQ

[Doris53]

This is for a bigger SU but it should be similar on your carb. You can see the 'clip' at the base of the brass outlet connection in this listing

https://www.ebay.ie/itm/255532995022?ha ... R7S_64XyYQ

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I have attached a couple of photos of my float bowl lid. So are those 2 grooves under that metal ring the vents?

[panky]

Ah completely different to what I posted, sorry, but I can't think of any other purpose for those grooves.

[geoberni]

That is the 'breather', it's clearly identified on the Burlen/SU website diagram.
https://sucarb.co.uk/technical-h-type-c ... er-diagram

[Doris53]

Excellent! Every day is a school day as the saying goes. Well, I shouldn't think there is much chance of that 'breather' ever getting blocked.