Engine running on choke only

[Mike]

I have a standard 2cv motor that will only run on choke.
I know every one going to say blocked carb but where.!!!
I have striped the carb down, blown through the jets and an many of the feeder holes I reach but still no joy!!!
Any advice ??

[callum]

Hi,
You need to determine if it's just idle, 1st choke or 2nd choke.

It sounds like idle, so the internal jets in the carb don't come into play as much.

Assuming that the float levels are correct, and that the fuel filter is clean and there's plentry fuel...

Take out and clean the idle jet on the outside front of the carb (8mm?) under where the fuel hose connects. Replace it. If this gets blocked, the car will not idle.

Then gently screw in the idle mixture screw (gently) on the front of the carb until fully home (count how many turns it takes). Now unscrew it approx 4 turns. That should be roughly in the right ball park. Start the engine and let it warm up. Adjust the mixture screw (either way) until engine reaches max revs.

That should be good enough to get you going. The internal jets in the carb don't come into play until the throttle is off idle.

If it's idling but not 'running' with a bit of throttle, then take out and clean the primary jet (recessed into the LHS fuel bowl and not immediately obvious). There's an access 'plug' on the outside LHS of the carb which allows better access. use a small screwdriver to unscrew it and a toothpick to extract it.

Rgrds
C

[Mike]

Hi Callum, Checked the idle jet, the holes at the bottom are clear but should the hole in the top of the jet go all the way through the jet and meet the bottom holes?
Adjusted the mixture screw.
Seems it still only runs on the choke, the throttle position has no effect.
Regards
Mike

[administrator]

Hi,
the hole in the end of the jet should connect to the three holes in the side. You should be able to blow down there and feel a bit of resistance.

Rgrds
C

[howardjs]

Just a thought... have you checked that the engine is not "sucking air" through a leaking manifold gasket, manifold to cylinders and carb to manifold.
Or a worn butterfly valve spindle.
H.

[Mike]

Hole through the jet is blocked!!
Tried poking a piece of wire through it but no luck.
Any ideas how to soften the blockage ?

[Ken Hanna]

Probably too late with the advice that fuel is drawn into the brass jet via that drilling so it's best to suck any blockage out, rather than try to blow it through, which is a mistake most folk seem to make.

Anyhow, the drilling is very small, usually less than 0.4mm in diameter, so perhaps you need a smaller implement at this stage.
It's probably worth having a look through any sewing equipment in the house, looking for the smallest needle in the box...

Ken

Hole through the jet is blocked!!
Tried poking a piece of wire through it but no luck.
Any ideas how to soften the blockage ?

[Jimmy Cooper]

I had a spate of that idle jet getting blocked creating same symptoms you have. Tiny hole that I figured was being blocked by possibly petrol lacquer? Cleaned it probably 4 - 5 times resorting eventually to leaving it in a small glass jar part filled spray degreaser (as used on brake surfaces etc) with a sealed lid and shaking it about a bit (ooohh err).
Seemed to have the right result as no issues since but I also fitted a large fuel filter just in case too.

[Mike]

Well the idle jet through hole is still blocked but it is idling fine!!
Only now it will not rev even with the choke!!
Put new points and condenser, spark plugs, set the static timing and it starts and tick over fine but will not rev!
If I feather the throttle I can get it up to about 2,000 rpm but after a few seconds it dies. let go of the throttle and it returns to tick over just as before!!

Plenty of fuel entering the carb cokes and butterfly's opening as normal so not a fuel issue.

Coil braking down under load maybe???

[Mike]

Change the coil and still the same