volvo 340 1.4 weber 104 carb fueling problem

[Cypher007]

i have the above car 1990 on a G plate. it has the weber 32 dir 104 variant. ive put a service kit on it as the previous owner had disconnected the choke and generally buggered about. anyway after putting the kit on the problem of "running rich when the revs were increased", was i thought cured. but it has returned and im not sure which bit of the carb controls the leaning out of the mixture when the revs are held at say 2k? tried tonight managed to get the carb to lean out, but noticed at one or two points the mixture went berzerk upto about 11-20% co, and the engine started running rough. this happened at idle and without me touching anything i had to rev it just to keep it running. when i let go the co and idle returned to normal. could it be something to do with the float? it happens instantly like a switch being thrown.

[vjck_uk]

Could well be the float needle worn or dirt coming through the line and holding the needle off its seat.
You could check the float level and adjust it a little anyway as the carb is probably worn a bit increasing the level.
As far as I know the only way of altering the mixture apart from the slow running mixture screw (which alters the mix up to 1/4 throttle) is changing the jets.

[pettaw]

Yep check the float level. Eye measuring is always, I think difficult, so I use a twist drill of as close to the thickness quoted as you can.

Hope that helps.

[srtames]

the fuel cut off solenoid controls the idle jet and can cause many odd symptoms when it sticks. The final cure is to saw 1/8 in off the end of the plunger and you get a much better idle and starting. the only downside is that you get running on when the engine is hot.

regards, Steve

I saw a post or article recently where the engine breather was blocked and this can cause the CO measurements you describe. Volvos are well-known for blocking their crankcase breathers.

Also there is supposed to be a restrictor in the breather hose from the top of the engine to the bottom of the carb, used at idle but not in loaded running. At one time there was no replacement available so even Volvo dealers were throwing away the old restrictor with the old hose, and fitting a new hose with no restrictor, then riching up the idle mixture lots to make it run as too much air was coming out of the breather and bypassing the carb at idle. When you rev to 2-3k with no load this will make the mixture go very rich as the amount air coming thrigh the breather has not changed but the amount of super-rich mixture coming through the carb has trebled. See where I am going.

Check the hose by blowing through it. Don't suck - it tastes horrible

Just a thought for you to try?