Engine runs for 10 mins then dies

[alainmoran]

OK, so I recently took my engine out to replace the gearbox, and now that I've put it back in it will run for about 10 minutes then cut out .. if you give it full choke it will then start after a bit, and run for another 10 mins.

When it dies it just dies, no coughing it just fades out.

The engine was fine before I changed the gearbox (it's also had new oil, fuel & air filters and fresh oil).

I'm at a loss as to what's happened ... heylp!

[bmcecosse]

Vacuum forming in the fuel tank ? Is the fuel pump ticking away like mad - trying to pull up fuel - or -is it deathly quiet ?

[MarkyB]

Might be an air leak.
Did you replace the manifold gasket?
If you had the carb out and laid it at an angle the silt from the float bowl may have migrated to the tube to the main jet.
This happened to me after an engine rebuild.

[alainmoran]

The fuel filter has plenty of fuel in it and the fuel pump is just normal, I've not had a vacuum in the tank before either.

I've not replaced the manifold gasket or had the carb off, but the engine has been tilted, so the silt idea could well be the cause ... I guess it's time to take the carb off and strip it.

[Jefftav]

Are you just letting it tick over for 10mins when it cuts out. If yes the carb could be flooding which might be disturbed silt as a previous poster has stated.

[bmcecosse]

Sounds to me like it's just using up the fuel in the bowl - then stops. The re-starting somehow 'primes up' the pump for another few minutes of running. It's definitely going to be fuel related. SUs normally cope well with any dirt in the bowl etc - what happens if you rev it up - does it still run 10 minutes - or does it cut out after 2 ??

[alainmoran]

Runs fine when revving, it only seems to die when it's close to tickover. It's definitely not using up the fuel in the bowl since there is fuel in the transparent fuel filter (after the pump, before the bowl and changed a week ago).

Dirt does sound likely though since the engine has been moved about a fair bit ... time to strip my carb then

[autolycus]

It's definitely not using up the fuel in the bowl since there is fuel in the transparent fuel filter (after the pump, before the bowl and changed a week ago).

Hmm. What if the float or valve was sticking? Might be worth very carefully lifting the float chamber lid after the engine has stopped to see whether there's petrol in the chamber. Or try tapping the side of the bowl after the engine's stopped, to see if it provokes a healthy rattle from the petrol pump.

Or are you saying it will run indefinitely if you hold it at fast tickover? Twiddle the idle screw if you'd get bored trying to keep the throttle open any other way.

Dirt does sound likely though since the engine has been moved about a fair bit ... time to strip my carb then

SU carbs are remarkably tolerant of dirt - far better than those awful tube-with-a-hole-in-the-side things that everyone from Austin to Rolls-Royce used in the early fifties.

Kevin

[bmcecosse]

Is it not just maybe running rich at idle - and slowly choking itself to death! You say it's fine if revved up - so i would set the idle timing and mixture up - so it has a nice steady idle - and don't set it to slow - better to be slightly fast idle in winter to keep water going round the heater - and the battery charged.