Running rich how to fix

Hi guys

have a slight issue my 1989  auto cabby is running rich , you can smell the unburnt fuel and when you turn it off, it runs on and then backfires.

Is this a job for a specialist? Or could I fix my knoweledge on cars is ok.

Any help would be great

Thanks guys and girls

Skye

Adjusting the mixture is easy, but I can't believe you can tell how far out it is by smelling. Also, running on after or backfiring isn't a symptom of rich running.

the running on is usually the cut off valve in the carb sticking..

if you want to sort out the mixture grab yourself a colourtune from a machine mart as if you lean it off too much you'll get detonation and that can be very bad news

a colourtune will set ya back about 25 quid and is a life saver

you can only adjust the idol mix though, the throttle mix isnt adjustable without re-jetting so i would assume the rich smell is when your car is on tick over?

also wobble the carb a little cos they sit on a rubber gasket which can tear with age and if this has tore it can let air out making your car run rich

just a few bits for yo to try bearing in mind im only using guess work as i have a small block

hope some of it helps any way

I'm going to guess its either Pieburg or Weber carb, I can assure you mixture is adjustable on either of these carbs!

but isnt it only the idol mix? i was only guessing mind you as i have a small block wid solex

Are you asking, if the mixture adjustment is the idle adjustment?

no,

i thought the mix screw is only to adjust the idol mixture, once the throttle opens it moves from the idol jet to the main jet,
i was under the impression the main mix cannot be adjusted and is set by the main jet…

this may be on the solex carbs tho..

Aha - I see what you mean. Well, its up to the OP to confim/deny if its the mixture at fault anyway. And if so, is it running rich (or lean) at idle, or full throttle, or half throttle etc etc and if so, how on earth has he measured it at those points????

lol its why i said for him to get a colour tune. there wicked for a quick tune up

Yeah it happens on tick over. U say it's easy to adjust the mixture can u explain or should o grab a haynes manual?

Thanks guys

if its a 2e2 the screw on the top is mixture only, the idle is adjusted by either bending a metal arm that contacts the pull down or adjusting the pulldown itself.  if its a webber then there are seperate idle and mixture screws.

the running on could be a symptom of runnign rich if its been doing it for a while, you'll end up with a lot of carbon buildup which causes hot spots in the cylinder and run on.  my old mk2 did this because the autochoke had been knackered for years hence loads of carbon buildup. fixed the carb then did the water trick to clean all the carbon out the cylinders and it never did it again.

if its the 2e2 then there could be several reasons why its running rich, fiddling with the mixture screw could just work around the issue and cause problems elsewhere.  if  you feel like it have a read thru my 2e2 faq post, but if you arnt mechanically minded it might be time to get a webber replacement, or ask to see if anyone is local to you who can help!  might be worth printing out the guide and taking it to your local freindly garage otherwise, but they might not be inclined to bother with it ans just change the carby instead.