Can you work this out?

This has had loads to time and mechanics look at the problem and can't get to the bottom of it?
So the set up is a Series 1 with a V8, running SU carbs on a V8 3.5 block and 3.9 top and bottom end.

Start's on the key hot and cold weather, and runs well. but once it's up to temperature and you turn it off, (ie fill with fuel) it will not start until it cools down again.
I have tried Swapping out the two carbs for another pair, same problems
I have tried three different Fuel pumps, same problem
Checked the coil, it was ok. (also tried running a 12v feed wire straight from batterie to double check)
Tried new fuel lines.
Tried two different types of fuel filters, both the same results
Someone said run fuel line out side of chassie and in from the front to make sure the pipe stays cool to stop air locks. about to try. but to day I turned LR off but opened bonnet and left the fuel pump running, so it was constantly circulating, still wouldn't start, so took air filter off and poured to petrol down carbs. didn't start.
any one got any ideas ?

You've not said if you've checked for a spark when it's hot and not starting...

Agreed, points or electronic? Try the condenser, just because they fail and they are cheap.

And how did you check the coil? Did you check when it was hot?

Does sound like vapour lock caused by overly hot fuel lines. You say you left the fuel pump on to circulate the fuel. I know diesel engines feed fuel back from the injectors to the tank but didn't think that was common on cars with carburetors?

kermit_rr said:

You've not said if you've checked for a spark when it's hot and not starting...

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Yes sorry a good spark at the king lead, and at the plug.

Gord Wedman said:

Does sound like vapour lock caused by overly hot fuel lines. You say you left the fuel pump on to circulate the fuel. I know diesel engines feed fuel back from the injectors to the tank but didn't think that was common on cars with carburetors?

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Yes the Su has a return pipe to the tank, it is a smaller diameter to give pressure to the carbs but will return to the tank.
I have brought some pipe to try a cooler route.

You're getting a spark and you've poured petrol down the carbs and it still doesn't start, i suppose you could be flooding it, spraying easy start instead might work while someone else is turning the key.
If it's not even giving a cough then rerouting the fuel line can wait

My camper van used to do the same and the problem was a dodgy earth from battery to block, I replaced it with welding cable and it never did it again.

I would defo a try a new coil, I think a spark in the open air is not the same as one under pressure.

Try some easy start when it won't run. If it runs with that then you can rule out the electric side of things and you are back to fuel starvation. My money is on fuel vaporisation due to heat soak from the engine.

Try a quality rotor arm. Some of the pattern ones arm very poor. Is it points or electronic dizzy? If its electronic it could be the amplifier (usually a little black box on the side of the dizzy - sometimes remotely fitted near the coil on earlier versions).
How are your plug leads? Someone once said to me 95% of SU carb problems are electrical...

Do we have an answer to points or electronic yet? Its hard to answer without knowing.

will it not start every time or just some times? If you turn it off and straight back on does it start? I would play with the easy-start if it fires or runs then fuel if not electrics you need to find this out before anything else, good luck finding it

rob1miles said:

Agreed, points or electronic? Try the condenser, just because they fail and they are cheap.

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its electronic so I think is doesn't have one?

Ian M in France said:

will it not start every time or just some times? If you turn it off and straight back on does it start? I would play with the easy-start if it fires or runs then fuel if not electrics you need to find this out before anything else, good luck finding it

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yes if you turn it off and start it straight away it normally does catch most time but its a bit hit and miss.

When hot and you crank the engine over it does sort of splutter like the timing was out but just will not catch.

wireman said:

Try a quality rotor arm. Some of the pattern ones arm very poor. Is it points or electronic dizzy? If its electronic it could be the amplifier (usually a little black box on the side of the dizzy - sometimes remotely fitted near the coil on earlier versions).
How are your plug leads? Someone once said to me 95% of SU carb problems are electrical...

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ill try a different rota, as that an easy job. thanks
this is the set up I did have a little aluminium heat thing on the wing near coil but it was trouble so replaced set up to this one.

fuel line is the one on the top of the bell housing going in on the left carb and returning from the right

kermit_rr said:

You're getting a spark and you've poured petrol down the carbs and it still doesn't start, i suppose you could be flooding it, spraying easy start instead might work while someone else is turning the key.
If it's not even giving a cough then rerouting the fuel line can wait

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It does cough a bit when cracking over,
I just tried adding more fuel to intake and after a long time it did fire up. but not sure if that answers anything?

Start it up in the dark, lift the bonnet and look for arcing/earthing from the ignition system, replace any duff parts. Check your dizzy cap, again, some pattern parts are cr@p.

wireman said:

Start it up in the dark, lift the bonnet and look for arcing/earthing from the ignition system, replace any duff parts. Check your dizzy cap, again, some pattern parts are cr@p.

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thanks i'll give that a go, all item are new but I know that doesn't mean a lot with todays car parts.