Petrol 1.9 carb engine won't idle

[brookie]

My mate heard a bang (he can't tell if it was mechanical or exhaust back-fire) and engine stalled. He started it again but it won't idle. The only way he can keep it going is by keeping his foot on the accelerator and keeping revs high.
I've had a quick look and it runs smooth enough but you have to keep the accelerator linkage on carb 'applied' to say the least as it stalls immediately when you let go.
Tomorrow we're gonna look at the main and secondary jets for blocking and will check the idle bypass shut-off valve incase it's failed 'shut'.
Is there anything else which would be a real fave culprit to cause such a sudden fault? It has been running perfectly for 12 months when we replaced plugs,leads, air filter, vacuum unit and very recently a fuel filter.
Any ideas and quick fixes gratefully received!
Oh, he runs an E reg 1.9 Carb water cooled E3 type carburettor.
Ta. Brookie

[Fritz]

A good blow through with the top off the carb will do it a world of good,,,,just have a good butchers at the bottom of the float bowl for those tell tail bits of shyte, which may indicate why the beastie isn't idling as it should.


Regards


Fritz,,,,,,

[stuckin88]

You can try squirting in Wynns carb. cleaner--but normally the only permanent solutions to blocked jets-(I'm guessing thats what it is)-is to remove top of carb & clean out float bowl-there will probabley be a lot of crud in the bottom--

[toomanytoys]

The idle cut off fails open, ie lets air into the idle circuit as if you have switched off ignition, most likely cause of the problem, but worth cleaning out the carb in anycase.. check also the backfire hasnt blown any hoses off the back of the carb, this will make it run lean and the vac advance unit on the distributor is still ok, they dont like high back pressure and when not working will give idle problems..

[Mocki]

i'm with Si on the vac pipes....... i bet at least one has been blown off.....

[Brooksie]

If all hoses are still on and the vac advance is OK it could be that the backfire could have shaken the timing if the dizzy wasn't tight enough. Check and adjust the idle, oh and worth checking the exhaust/box for splits. Good luck

[brookie]

Thanks guys for all that.
Did find that the timing was slightly out ( I suppose it is possible it might have shifted if it was a big back-fire but this must be rare?) Anyway, with timing set to 5 degs btdc with vac disconnected everything is back to normal. We found a small amount of crud in float bowl, cleaned it out and checked the jets which appeared clear. None of the vac hoses had come off so it was a strange fix but at least my mate is now clued up on carbs and timing so he won't need to call me for a little while!
Good tip on the exhaust Brooksie as low and behold I found a death crack on inlet side of silencer stub! Another job for him to do.........

Cheers all.

[vanjam]

so is it cured? some extremely useful sounding expertise posted there but is it fixed?

[brookie]

Yep, the van's behaved itself all weekend as if nothing were amiss!