dripping carb

[administrator]

Hi,
I've noticed, that when I turn my 602 engine off, I get a lot of fuel dripping from the bottom of the manifold over the hot engine - more than I would expect.

I've cleaned the carb and checked the float heights (18mm) and the car runs a lot better than it did, but the dripping fuel concerns me.

I've also found that the idle mixture screen is turned 7 full turns out - which seems excessive and may be related? Now that the wheels will stay on, I can take it for a decent drive and get the engine properly warm and try to adjust the idle mixture, but don't know if that is causing the issue.

Any ideas?

Rgrds
Callum

[Ken Hanna]

Callum,
could be the needle jet showing its age?
How does the engine cope with an extended period of ticking over? If it slows down and stops after a few minutes, this could indicate that the needle jet isn't sealing correctly, which allows the fuel level in the float bowls to gradually rise.
Might be worth check that the needle jet is screwed tightly into the carb lid, as well...

Re. the setting of the idle mixture screw, have you made sure that the secondary butterfly is closing fully? If not, 'false' air can leak past it, which means that the idle mixture needs to be set very rich.
Clip the top off the plastic cover on the 'anti-tamper' screw, usually located on the nearside, then back the screw off by one turn. (see attached photograph)
'Blip' the throttle a few times with the engine running, then re-adjust the tickover screw and idle mixture screw with the engine warmed up.
( These adjustments do not have any effect on the 'post shut-off' flooding problem, btw.)

primary petrol jet position by slcchassis, on Flickr

[callum]

>How does the engine cope with an extended period of ticking over? If it slows down and stops after a few minutes,

Ken - that describes it perfectly. At first, I thought that perhaps I had a sticky float - the float arms is fairly well modified, but it does appear to be flooding the manifold through the top of the carb.

I've held the lid up and blown through the fuel pipe, and the needle valve does close, but it's easy enough to swap it out with a new one and test that.

There was a lot of crud in the carb bowls causing the primary jet to 'stutter', but that seems to be resolved. Perhaps some of that crud is still stuck behind the needle valve.

I'll have a 'play' with it tonight and see if there's any improvement.

Rgrds
Callum

[callum]

Ken,
Needle valve seemed fine, but what I did notice was that the spindle that the floats pivots on was very worn, allowing the float mechanism to twist. I suspect that was the issue. I knocked the brass pivot out and replaced it with another. The shoulder at one end of the pivot was almost worn away to the diameter of the pivot, allowing greater movement of the float movement.

So far, everything seems fine.

I also unscrewed the idle mixture screw to find the needle end bent. Replaced that with another and now the car starts and idles better.

Long test run on Thursday night, so will know for definite after that.

Rgrds
Callum

[Highwaylass]

Callum, how did you knock out the spindle? I want to replace the float on my 2CV carb but the spindle is very tight, I tried it with a hammer but it refuses to budge.

[callum]

Hi,
I just knocked it out from one end using a pin punch. It did come out easier from one end than the other.

I don't think a new set of floats comes with the spindle - you have to re-use the spindle.

Rgrds
Callum

[Highwaylass]

Thanks! I have both new floats and new spindle, just couldn't fit them..