Replaced carb diaphragms and now won't start

[Eric B]

Just replaced both Stromberg diaphragms and now the car will not even start! I had a slight misfire and 4 of the plugs had a lot of black soot so I replaced the diaphragms (both sides). Seems I have taken a step backwards rather than forwards! Any suggestions?

[Lingen]

Eric.
Were all four black plugs on cylinders supplied by the same carburettor? And if it isn't rude to ask, did you replace the diaphragms correctly with the "Tags" located in the notches in the pistons and carb bodies?
Mike.

[trunt]

Talking of backwards.. sure you got them in the right way round? There are small detents on the piston and the carb body that align with small tabs in the diaphragm. This needs to be correct or else the piston will not be aligned correctly.. could cause problems if it’s not right.

*edit. What Mike said while I was typing!


Terry

[jbuckl]

+ 1 for the stromberg piston orientation.
once that is checked & confirmed, check cylinder compressions.
check fuel is present at the bridge.
then check for a spark.

[Eric B]

Thanks everyone - Mike - yes the right hand carb was the one linked to the soot covered plugs. I'll retrace my steps to check the tabs are in alignment as suggested in the replies - I thought they were, and will see if that helps.
Thanks again
Eric

[Jeff]

Bear in mind that each carb feeds two cylinders on each bank - not all the cylinders on that side.

[richardthestag]

Carbs - Inlet manifold.jpg

[jbuckl]

Thanks everyone - Mike - yes the right hand carb was the one linked to the soot covered plugs. I'll retrace my steps to check the tabs are in alignment as suggested in the replies - I thought they were, and will see if that helps.
Thanks again
Eric

Check the fuel at the bridge; check with elbows and air filter off.
under & over fuelling easy to spot as the revs rise & pistons lift. Also easy to check carb piston rises and falls smoothly too.
block the vacuum take off for the thermac. The one way valve inside the take off usually leaks as the spring & ball corrodes.

[ethel]

I think a while back there was someone who had a problem with their carbs due to excess powder on the new diaphragms which is used to stop them sticking to each other or their packaging.

John.

[Rod1883]

I've recently fitted new diaphragms whilst replacing the metering needle adjusting screws and seals to fix oil loss from the dashpots. My new diaphragms were thickly coated in the white powder (some sort of chalk?) which I carefully wiped off before fitting. The car is running far more smoothly since the work.

[Roy_S]

Be interested in the feedback on this Eric as will be fitting thwo new ones to mine soon.