Getting used to using a choke!

[Velorum]

Originally Posted by john h

Note for Steve:

When a car is warmed up by ticking over, you will gradually dilute the engine oil. Some excess fuel will wash down the cylinder walls into the sump. This is why almost all car manufacturers advise that the car is driven to warm it up (takes less time, and more of the extra fuel is burnt).

I realise you can't drive your 240 yet. It's not a big problem, provided that you change the oil every few months, even at zero miles, if the engine has been repeatedly warmed up with the car standing. A quick check is to pull out the dipstick and smell the oil. If there is any smell of petrol, it needs changing.

It might be better to turn the engine over on a regular basis with the coil HT lead disconnected so that it doent fire up. This would avoid combustion problems whilst keeping internal parts freed up.

[Steve and his 244]

hmmm, well I didnt know that (john)!

We will be giving the car a full service in the near future but in the meantime I will check the dipstick as you mentioned. I must say though, whenever the car is started I always sit in it (for up to 20 minutes) making the engine warm up to operating temperatureand then leaving it running for a while longer

Ian, I could do that but like I said, I always completely warm up the car

[Paul240480]

The 340 carbs are prone to warping where they fit to the engine, allowing air leaks and causing all sorts of probs with tick -over, choke issues and so on. My 'old Indie' used to make a 'paper' gasket & re-site the carb to solve this. I THINK the full fix is to have one (or both) of the 'mating faces' skimmed.

[pettaw]

Carbs particularly on 1.7s are very prone to warping on the base. This was caused by a bad design when they were first out leading to hot spots. Volvo brought out a much thicker base gasket towards the end of manufacture in 1991 IIRC. You can retrofit this thicker green gasket to the earlier cars but I'll bet that 90% of cars will already have had this done. As Paul says the 'proper' fix is to skim the faces on both the carb and the manifold, but mostly the carb cos the manifolds don't warp much. I managed to very carefully file the flange of the manifold flat without taking it off the car to cure the airleaks on ours after exchanging the carburettor for one with a flat flange.

The 1.4s don't seem to suffer this problem. I would say the choke characteristics are different on all the engine types. The 1.4 seems to be least sensitive to it and you can push in quite a way and almost all the way within a few minutes, but the 1.7 needs to be thoroughly warm before the choke can go all the way in from our experience.

Just a quick note on setting up the mixtures without a CO meter. The best way to do it is basically as the poster earlier said it. Set to max RPM and then reset idle to approx 950 RPM. That will get you to about 5-6% CO. Then you reduce the mixture screw slowly until you hear the engine revs just start to drop very slightly. If you have an RPM gauge it should drop approx 50rpm. That will get you inside the 3.5% for the MOT test.

[foggyjames]

My experience has been that cars with a relatively large carb are much less fussy about choke settings. It may be pure co-incidence, but my (potentially fussy with the original carb) 360 can be run without any enrichment at all now it has the twin carbs on it (no surprise...I believe most Weber DCOEs don't even have an enrichment circuit), and my 340 1.4 (which has a relatively large carb.....32/32mm barrels, against 28/34mm for the 340 1.7 and 34/34mm for the 360 2.0!) can usually be run with no choke at all at a push.

I suspect there is a slight difference in adjustment between the two cars. 1.4s should be very forgiving of an incorrectly set choke...so whichever is giving you more trouble is likely to be the one which is wrong.

cheers

James

[Clan]

Your B14 should have 22/22 or 22/24 chokes where did the 32/32 come from?
Regarding Weber DCOE carbs , they do have a choke lever but generaly competition engines are set up slightly richer than road going ones so they are not used and you only need a couple of pumps from the accelerator pump jets to get it started , usualy short manifold pipes on these type engines don't lead to fuel condensing on the manifold walls when cold either so drive away from cold nicely ..

[foggyjames]

32mm barrels...the chokes / venturis are the things which fit inside them, and are smaller. I don't know what size they are from the factory, to be honest, but low 20s sounds about right.

My Solex ADDHE 40s (DCOE 40 copies) have an enrichment circuit which works better than stabbing the throttle when starting...but it's pretty much redundant once the engine has been running for 5-10s. Those carbs have 40mm barrels, with 32mm venturis / chokes, going back to my earlier point.

It appears on the face of it that barrel size (which is the number usually quoted in the carb model number....i.e. Weber DIR32 for the 1.4) is the thing which has the effect on choke sensitivity. Presumably because the choke flap is bigger to match! Why that matters, I'm not sure....carb experts?

cheers

James

[James A]

My old 240GL had a carb and a manual choke, although the latter was rarely needed for very long, even in really cold weather. It used to suffer from carburettor icing a lot, though!