Technical Carb problems - running too rich

[turbo_jim]

As mentioned in my earlier thread, my car is running extremely rich and suffers from horrendous flatspots. I've stripped , cleaned and reassembled the carb but it remains much the same, making it almost undriveable. I didnt use a rebuild kit, but all components looked in good condition, and there wasnt really any dirt to speak of in the carb.

My questions are:
1) Is it worth spending £30 for a rebuild kit and stripping the carb again in case there is a problem with eg. the needle valve?
2)could the problem be simply down to the ignition timing being out? The points don't look too bad and the engine fires ok

This is really frustrating me at the moment as I am unable to use the car - I've never had this much trouble from a carburettor before, although this is my first experience with webers.

cheers,
Jim

 

[jimbro1000]

The richness of the mixture, when above idle is controlled by the main jets and the float level.

If the wrong jets are fitted it will be off, equally if the float level is too high (or low) it will be off. A rich mixture would be the float too high either as a result of the setting or the needle valve leaking.

Running rich at idle is controlled by the choke (fast idle) and idle mixture screw (slow idle).

If it is definitely running rich then the solution is to check the carb again and if necessary replace the needle valve and float.

If the flat spots are not down to fuel mix then it could be either cam timing or ignition timing. A general lack of power at top end would be the cam, if the flat spots are all over the place then it would be ignition.

 

[Neojames2k]

Oh dear, looks as if I have a problem with my float then , Guess what i'm doing this weekend

Cheers for the info Jimbro, I was gonna ask something along the lines of this question anyway

 

[turbo_jim]

When I stripped the carb the float was a bit high (and the two floats were at different heights) so I adjusted them according to haynes to ~7mm. I took the jets out again tonight to clean/check them again, and I found that the main jet fitted was 1.15mm whereas the spec in Haynes says it should be 1.07. Could this be the cause of my problem, or is it likely that someone has fitted a larger jet to try to overcome the problem?

I think I'll try and get hold of a 1.07 jet and fit it and then try and find someone to check the timing properly for me. Any other tips?

Cheers,
Jim

 

[erich]

When I stripped the carb the float was a bit high (and the two floats were at different heights) so I adjusted them according to haynes to ~7mm. I took the jets out again tonight to clean/check them again, and I found that the main jet fitted was 1.15mm whereas the spec in Haynes says it should be 1.07. Could this be the cause of my problem, or is it likely that someone has fitted a larger jet to try to overcome the problem?

I think I'll try and get hold of a 1.07 jet and fit it and then try and find someone to check the timing properly for me. Any other tips?

Cheers,
Jim

A 1.15 in place of a 1.07 will make it run rich, but not gruesomely so. Floats high and at different heights is much worse, and is evidence of seriously ham-handed botchery somewhere in the past (high is forgivable, but different levels?)

This is one of those situations where you should just fix everything that you know is wrong, then see what still doesn't work... And repeat... You can curse the previous owner devil::nutter and his mechanic nutter::devil while you're working.... It'll make you feel better. And webers are pretty resilient, once adjusted right they run well and stay right.

Get a fresh set of spark plugs too. They're cheap, and it's way easier to tune with good plugs than with ones that are fouled by previous over rich operation.

 

[turbo_jim]

I have definitely been cursing the previous owner, and the owner before that! My car has some very unusual bodges, and has manual switches on the dashboard for the radiator and carb fans....

I think I'll probably shell out for a full carb rebuild kit. Changine the spark plugs sounds a good idea too, although I cant find my spark plug wrench anywhere at the moment

Another problem I have is that the choke doesnt come off fully when hot. There is no dirt inside, and there is definitely water going through (I checked for airlocks). I adjusted it by rotating clockwise but then found that the pipes foul on the base of the K&N filter! Am considering reverting back to the standard air filter to see if this improves the situation (and if it makes a difference to general running of the engine).

Fix It Again Tomorrow....

 

[jimbro1000]

Before giving up on the autochoke check the linkage that goes to the throttle arm is properly adjusted - you've probably already done this but it is worth looking if you haven't

the manual overrides for the fans are pretty standard fare

 

[ppalma]

If your car has manual switches for the fans it surely means that it was overheating at some point in life. When cars overheat they lose cooling fluid, and the quick fix is to add water, which is not good for the X1/9's health.
Check that you actually have a thermostat, or better still, just replace it as it's a cheap item. Do the same to the expansion vessel's cap making sure you buy one of the correct pressure rating.
Your heater valve perished, so it's to be expected that the autochoke went the same way --> replace it!

 

[turbo_jim]

If your car has manual switches for the fans it surely means that it was overheating at some point in life. When cars overheat they lose cooling fluid, and the quick fix is to add water, which is not good for the X1/9's health.
Check that you actually have a thermostat, or better still, just replace it as it's a cheap item. Do the same to the expansion vessel's cap making sure you buy one of the correct pressure rating.
Your heater valve perished, so it's to be expected that the autochoke went the same way --> replace it!

That's an interesting point, and one I hadn't really considered. The car has recently had a reconditioned radiator so it's definitely had issues in the past. There is no evidence of oil/water contamination as far as I can see, so hopefully there has been no damage to the engine/ head gasket.

When you suggest replacing the choke, do you mean the bimetallic spring? Are these easy to get hold of?

Thanks again,
Jim

 

[ppalma]

Yes. A long time ago I bought a carburetor repair kit and it came with a new bimetallic spring, can't remember where I got it from, though. Webcon maybe?

P.S. Not so sure it came with the repair kit, I guess I ordered it separately.

 

[jimbro1000]

Southern Carburettors used to be the place to get such things from in the UK - and I think they are in Wimbledon, Webcon are pretty close too in South Harrow. Between the two of them I would be very surprised if you can't find the parts you need.

 

[Martygf]

I am also having the same problems with my carb in that the car is running too rich ( have to get it sorted for its first MOT in 11 years! ) I think i will have to resort to a rebuild kit but will try adjusting manually first. You could try www fastroadcars .co .uk which are a Weber carb specialist here in South Wales.

 

[jimbro1000]

While I remember the "repair kit" isn't a single item - there are actually 3 or 4 repair kits depending on the intended repair so make sure you get all of the parts you think you need. This might have changed since I last bought a Weber repair kit but I suspect otherwise.

 

[turbo_jim]

Have just ordered a rebuild kit from Eurosport - includes everything except for the choke diaphragm, and was slighlty cheaper than FastRoadCars. If this doesnt help then I am going to have to get it to a garage I think and leave it to the professionals!

 

[turbo_jim]

Update:

Have now discovered that my fuel cut-off valve isnt working - this should cut the engine immediately if disconnected, right?

Also, I have read that to set the idle/mixture correctly you need to warm the engine up and then prop the choke wide open. However with the choke completely open I cannot get the engine to idle at all, no matter what position the idle screw and mixture screw are in. I guess it's lucky that the autochoke only half works..

I'm going to rebuild the carb over the weekend (including a new float and needle valve). One more thing: there is a connection on the left of the carb (under the fuel pipes) which is not connected to anything(although it was covered witha rubber bung). If I remove the bung and put my finger on the hole with the engine running there is quite a strong vacuum, I guess this is for cars with vacuum advance on the distributor - should it be connected to anything on my car?

 

[TeamTowleMotorsports]

That vacuum connection should go to a carbon(coal) canister. if you don't have one i wouldn't worry about it. I just took my carbon canister out and capped off that line.

 

[turbo_jim]

Turns out that what Haynes says is an idle cut-off valve, is actually something that looks like a temp sender - presumably for the autochoke. In which case, what is the red wire coming out of my choke housing ?

 

[Neojames2k]

It's definitely a idle cutoff (anti dieseling) solenoid it's probably just not functional any more. I also have a red wire coming from my auto choke, not a clue what it does as yet, but i'll be playing with my carb tomorrow, I've got a problem with fuel usage (it's drinking the stuff) but I've got a feeling it's got something to do with the massive crack in my carb drip tray

Info about the mysterious red wire to follow (probably tomorrow late afternoon)

Cheers
Neojames2k

 

[littlephil]

do you mean the big brass thing under the carb at the back of the engine that the LIARS at haynes think is an anti-dieseling valve? If it is then that is the temp gauge for the carb cooling fan and has nothing to do with the running of the engine.

 

[turbo_jim]

do you mean the big brass thing under the carb at the back of the engine that the LIARS at haynes think is an anti-dieseling valve? If it is then that is the temp gauge for the carb cooling fan and has nothing to do with the running of the engine.

Thought as much. Back to the drawing board then...:bang: