Weber carb problems

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 22:06
Location: Near Leeds, United Kingdom
My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension.
x 1

Weber carb problems

Post by uhn113x »

Hi folks
Car: 1985 Series 1 BX16 auto - Weber carb with auto choke
Fault: Starts OK, hot or cold - after 10 secs, runs VERY rich, need to keep revving it - after driving a mile or so, fine. Emissions OK when hot, so slow running must be OK.
This fault has developed gradually - I overhauled carb about a year ago, and set up as per manual - worked fine for 6 months or so.
I have checked:
Choke pull-off diaphragm intact
Drilling in CPO casting
Float needle valve
Choke butterfly for sticking
Replaced wax stat on carb - no different
Checked for air in coolant pipes on same
If you take the elbow off the top and start it from cold, the choke comes off as you would expect it to - problem occurs when it is about 5mm open.
How far should the pull-down device move it?
And what is the black plastic thingy connected to the CPO device with a rubber tube?
I suspect a problem in this area, but to stop it flooding totally, have had to maladjust the choke so it comes off sooner, making it a trifle weak until thoroughly warmed up.
Any ideas, anyone?
Mike
User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 04:56
Location: Denmark
My Cars:
x 1

Post by AndersDK »

Hi Mike -
Fitted to the side on both Solex & Weber autochoke carbs - you have the odd square(ish) vacuum can. This is connected to the carb by either a 180deg bend short hose - or directly with a stud pipe and O-ring.
The purpose of this vacuum can is to help against strangling the carb during cold starts - just after start - by giving the strangler override vacuum actuator a delayed release - and a vacuum reservoir.
Either you have a leak here - or the strangler override actuator is leaking - not preventing an indeed too rich mixture just after start.
You may visit Bob Smith's homepage for further (genuine Citroen) documentation on the carb's used in the BX model range :
http://www.rwbsmith.plus.com/citroen2/
- plus a welth of other BX stuff [;)]
User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 22:06
Location: Near Leeds, United Kingdom
My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension.
x 1

Post by uhn113x »

Hi Anders
I was hoping you would pick up on this one! Your diagnosis sounds spot-on [:)]
Had a look at Bob's site - didn't know he had one! I have met Bob - knowledgeable guy.
I have never known what that little box was - it seems as though the choke flap should be pulled off much more, when the engine is running, so I must have a leak somewhere - should be easy to find.
Thanks again
Mike
User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 22:06
Location: Near Leeds, United Kingdom
My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension.
x 1

Post by uhn113x »

Hi Folks
Took carb off, and found that stub on antiflooding vacuum reservoir was cracked, and rubber pipe hardened. Turned up a brass stub and Araldited it in, should have cured in a few hours, so we will see if this has worked. Fingers crossed [:)]
Mike
jeremy
Posts: 3959
Joined: 20 Oct 2002, 16:00
Location: Hampshire, UK
My Cars:
x 2

Post by jeremy »

Araldite may be petrol soluble. Polyester resin (as used in fibreglass repair kits) certainly wasn't in leaded petrol and is probably strong enough.
Jeremy
User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 22:06
Location: Near Leeds, United Kingdom
My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension.
x 1

Post by uhn113x »

Hi Jeremy
Maybe - in theory there should not be any petrol near this bit, and I am only relying on the Araldite for sealing, not mechanical strength - the part I made is a flanged brass tube that is a tight push fit into the black thingy. Put carb back on this morning - adjusted stop on antiflooding capsule so choke flap opens 4.5 mm - this it did correctly 10 secs after starting, but it still seems to run rich, even with rubber elbow to air cleaner off, until it warms up more and choke comes off further.
If you open the choke manually when it is too rich - it seems OK.
Im becoming a tad baffled! Mixture is spot-on when warm, as per emissions test
[?]Mike [?]
User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 04:56
Location: Denmark
My Cars:
x 1

Post by AndersDK »

Mike -
From own experince with my carb'ed BX16TRS I know that the calibration/adjustment of the autochoke & strangler inhibitor is very critical.
When the engine is running at cold - try deduct exactly how much more the strangler (choke) flap must be opened to make it run clean.
This is the best pointer to your problem.
It's known that the vacuum actuator can be a swine to keep tight - and the terminal solution may be a replacement.
But my cards are on the nearly 20y's old membrane in the actuator.
Rep kits are still around for these carbs - covering a range of basic types. I think GSF may still have some lying around somewhere.
Either that - or they know where you can get a kit elsewhere.
The rep kit are not a dedicated Citroen spare - but a general Weber (or Solex) spare - as these carb types was used in huge quantities on many cars.
User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 22:06
Location: Near Leeds, United Kingdom
My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension.
x 1

Post by uhn113x »

Hi Anders
The diaphragm was replaced about 18 months ago when I got a kit from local carb sppecialist. There are no leaks now - if you take the device off, push the lever against the stop and block the pipe, it holds its vacuum. The device is working - it pulls back to the stop after about 10 seconds, opening the flap to 4.5mm, as I have set it per the manual. When it has run 20 secs longer, and is running rich, if you open the flap to about 10mm, it runs better - no eight-stroking. Are you saying I should unscrew the stop on the capsule so it opens to here?
I don't want this to be the first carburettor to beat me!
Mike
User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 04:56
Location: Denmark
My Cars:
x 1

Post by AndersDK »

This carb won't beat you Mike [8D]
- it's a Weber !
Your observation simply points to an offset in the adjustment.
When I did mine - I adjusted it in room temperature according to a workshop thermometer - and did a simple interpolation from the table in Haynes - to get it just exactly right.
Then I put it in the fridge together with the thermometer for 1hr or so - and checked again. Turned out I had to slightly correct the adjustment.
The problem could well be the calibration of the throttle (bottom) flap (idle speed setting) - as this has it's own adjustment working off the autochoke. This is a locked adjuster screw.
To be honest I fine tuned my carb by "feeling" on car - as the clockwork mechanism always are a bit worn here & there.
Patience - and you'll get there [;)]
User avatar
uhn113x
Posts: 1161
Joined: 06 Jan 2004, 22:06
Location: Near Leeds, United Kingdom
My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension.
x 1

Post by uhn113x »

Anders
Thanks for all your info - I did set it using a vernier caliper for the lever-to roller distance, and drills for the flutterby clearances, including the first choke 'fast idle' screw (set this open more than manual) - this was done at 15 degrees C in the workshop interpolated figures for 10 and 15 - not tried fridge! Not enough points yet!
The holy grail I am after is that I can start it up at 5 degrees below zero, and have a coffee while it warms up, just like I can with my DS, although that is injection. It always used to - I have had it since 1997. Now it will either flood or stall. I would love to get my hands on a spare carb, even a Solex, but they are few and far between. If I get frustrated enough, I may design a manual choke for it, but would prefer to keep it original.
Mike
Post Reply