v8 won't restart when hot. engine floods.why?

[jasper110]

i've a problem with my 110 3.5 V8 stromberg carbs. when the engine is hot after a run and it's left for about half an hour, it won't restart and the engine floods (or at least i think it does) it will turn over no problem but it just won't fire. what i would like to know is; why does it happen and what can i do to prevent it and get the landie started? although i also run LPG. the problem is only on petrol and always has been.

thanks.

[PhilipA]

This problem can be a few things
1 needle and seat worn out so fuel leaks into the carbs and then into the engine. ( fix-replace needle and seat)
This should not happen if the fuel return to the tank is unobstructed/still there. ( fix- check fuel return is connected/clear)
2 The fuel is evaporating out of the fuel bowls due to heat soak. They will all do this to some extent. ( fix-insulate fuel line, check routing to be away from hot areas like exhaust)
3 A vapour lock forms in the fuel line due to heat soak, along with the fuel evaporating out of the bowls. ( ditto above)
4 A weak ignition/old plugs can contribute to the problem as will not fire a rich/weak mixture.
Regards Philip A

[jasper110]

thanks Philip. it's not 4 for certain as the ignition side of things is pretty new. the fuel return is good. what would you suggest that i insulate the fuel lines with?

[jimbo110]

My '89 V8 was the same. Sometimes took 20-30 seconds of cranking to get it to fire when hot. changed to SU carbs, problems gone

[PhilipA]

Well, maybe try some rubber hose, split over the pipe running to the fuel filter, then some reflective aluminium tape.
I would look at he route of the rubber hose from the fuel filter and route it around the front of the engine away from the exhaust.
Maybe a heat shield made from aluminium sheet between the pipes and exhaust would also help.
But you will always have at least 80-90 C from the ambient in the engine bay. Try some premium fuel as it has a higher flash point.
If all else fails try pouring some cold water on the pipes and see if it helps.
A bonnet vent may help.
One other thing you could look at is to see if that bloody Heath Robinson heat diverter from the exhaust manifold is working properly. Ie if it is open it will channel hot air to the carbs. After all that remember its a small engine bay with a big engine.
Regards Philip A

[Blknight.aus]

I'll back all of phillipA's answers

to decide weather its flooding or vapor locking, get it nice and hot, take the airfilters off, close the hood and wait your nominal 20 mins....

have someone else stomp the loud pedal while you look down the throats of the carbie and see if you get a squirt of fuel....

if you do more than likely your flooding from residual line pressure leaking past the needle and seat and sitting in the inlet manifolds.

If you dont your vapour locking and the simple solution is to fit a "ticker" type fuel pump after the normal pump and then turn it on for 5 or so seconds before you try to start it up...

servicing the carbs can only help either case as well.

[100I]

If it is flooding, hot start with the throttle open.

[jasper110]

If it is flooding, hot start with the throttle open.


ok. will try that