Hi, i have a 87 1500 which starts fine and after the choke comes off seems to run ok [no MOT at the moment so cannot drive it far]The problem is that after i start it i need it keep the revs up or the car will choke up a eventually stall

Any help thanks Shaun

If yours is a carburetor version with automatic choke (UK 87?!), then I would suggest one of the jets is clogged. Try replacing the fuel filter if you don't remember when it was last replaced, get the engine running without the air filter and block the carburetor air intake while accelerating. The sudden pressure drop just may clear the jet. No idea if or why it is necessary to remove the air filter, just seen it done like that once. You can try doing it without removing the filter first, as it is safer and easier.

Thanks ppalma,sorry it is carb with auto choke i will try that thanks

When you say you need to keep the revs up can you elaborate a little?

What revs is it trying to run at while on choke? What revs do you need to keep it at to stop it stalling?

This could just be a case of a few quick adjustments rather than a blocked jet...

Hi Jimbro,

If i start the car and leave it running it ticks over at about 1000 rpm and gradually starts misfiring and stops.

I can keep the revs up to about 2500 rpm and i can hear the plugs clearing and when the choke comes off it seems to run fine

Hope this helps

1000 rpm sounds pretty low when starting from cold. Maybe Jimbro is right and you only need to adjust the idle speed. Or maybe it's the ignition timing that's way off. Your distributor should have a mechanical contact-breaker. and these do wear out and cause changes to the ignition timing.

Thanks ppalma

I have a timing light and will check points etc as well

One of the things people seem to forget is that the points and condenser work together as a single unit. If you find you need to replace the points then make sure you swap the condenser out at the same time otherwise the points will be in need of replacing again very quickly.

As already mentioned 1000rpm is way too low for a cold idle.
Check the timing (with the engined warmed up and the plugs clean) and make sure the timing is where it should be. If it is then you need to check two things on the autochoke. First up - is it working at all. The system isn't actually an autochoke, it is a semi-auto choke - you have to prime it first with two presses of the throttle pedal. This dumps two squirts of fuel down the choke and more importantly resets the position of the choke arm to the right position for the temperature of the coolant. If you take the air filter housing off and look at the carb you should be able to see the choke arm poking into the autochoke thermostat housing. If you work the throttle by hand (with the engine cold and untouched since cooling down) you will see the choke arm moves with the throttle but when it is released it stays part-way out. If it goes all the way back in then you need to check the thermostat on the side of the carb, if it stays out a bit then you need to adjust the arm itself.

Tackling the first one - give the water pipes to the thermostat housing a good squeeze. If they sound like an empty crisp packet the odds are the problem is lack of coolant getting to the thermostat and a substantial accumulation of chalk (just like a kettle). A lot of cars fail to pump water to the autochoke because it is the highest point in the cooling system and airlocks very easily. If you jack the rear of the car up the pipes actually make the best place to bleed the cooling system from. I don't normally recommend running an engine with the car jacked up but this is one scenario where it is actually a good idea. So getting back on track you need to do two things here: 1) Get the pipes cleaned of chalk or replaced; and 2) bleed the cooling system from the autochoke end of the pipes to make sure water is circulating through the housing. In most cases this will solve the problem but if it still doesn't work then it is possible the bimetal spring in the housing has snapped in which case all you can do is replace the housing.

If you have to take the housing off make sure you mark the position - rotating the housing adjusts how long the choke stays on for and what temperature it stops working at.

Adjusting the choke arm is one of the easiest jobs on the carb but only if the arm thread is in good condition. The outer end of the arm should have a slotted screw head (like a grub screw). Tightening the thread increases the choke throttle position, loosening it reduces the position. Simple enough but I've seen more than a few with one side of the arm head snapped off. A pair of locking pliers will get you out of a fix but the threaded part of the arm should be replaced.

All of the above advice means nothing if the carb is not in good working order to start with. Unlike some other makes of carb the weber carburettor is not self-correcting or particularly adjustable without a lot of messing.

The two adjustments mentioned above are all you can do for fast idle adjustment. For slow idle there is just the throttle stop and a small needle screw in the base of the carb for idle mixture. Everything else requires dismantling the carb to some extent. Foremost is the float chamber level - this governs the fuel air mix once the idle circuit stops working, get it wrong and all the messing in the world will not sort it out. In a close second are the jets and emulsion tubes. If the float chamber is correct and there are no air leaks or blockages the jet should limit the amount of fuel coming out of the float chamber and into the venturi but this is also adjusted by the emulsion tubes which partially mix the fuel with air (this is where the float level is so critical).

This may sound a bit like a lecture but I have a big point to make - if the minor adjustments I've already mentioned don't get the choke working then unless you *really* know what you're doing then best thing to do is to get the car to an expert. A rolling road is the best place but old-school carb experts are getting rare as hens-teeth these days as they all rely on electro-gadgetry to run the engine management diagnostics and if it doesn't have a turbo on the side most aren't interested. The weber dealer for the uk (used to be southern carburettors in leighton buzzard iirc) are a good place to make an enquiry on who to turn to.

Thanks again Jimbro

I have new plugs,points,rotor arm,condenser and cap.I have drained the system and made sure the all the pipes get hot including the ones to the choke the fan cuts in and the heater gets hot, we have a fancy bit of kit at work called a Vacula which sucks all the air out of the system and then sucks anti freeze back in.I will try the adjustments you mentioned and if no better i will try and find a specialist in my area

Thanks for the advice Shaun

Hi, just a quick update i have checked the timing with a strobe light and it needed adjusting along with the tick over which rest at about 1000 rpm now.I will wait until tomorrow to start it up from cold to see about the choke.

Hi Jimbro i am a bit confused when you say [choke arm poking into the autochoke thermostat housing] is this what you mean

shaun said:

Hi Jimbro i am a bit confused when you say [choke arm poking into the autochoke thermostat housing] is this what you mean

Click to expand...

Close, but sadly no cigar this time. That is (ultimately) the other end of the choke arm. If you spun the carb around 90 degrees clockwise you'd see the bit I'm talking about.

The thermostat housing is the round lump on the side of the carb (nearest the camera in your picture). It splits into two parts, the coolant housing (with two pipe connectors) is the outermost piece. The spring and control cam is the inner part.

The choke control arm fits into a small apperture in the side of the inner part of the thermostat and rests against the control cam. The cam itself is stepped so as it warms (and rotates) the arm can slide in but if it were to cool the cam will jam against the arm until the throttle is opened, at which point the arm is pulled out, allowing the cam to rotate (this is what has to happen when you prime the throttle from cold).



You can just see the arm in this picture, you can also see the slotted head and thread on the arm that allows adjustment. Thanks to midwest-bayless for providing the picture!

Is this it

That's the one

Thanks i will have a look today

The choke arm returns to the stop position and does not stay out.do i need to take the choke housing off and see what the problem is inside?

Does that mean all this time i was trying to start the car with the choke not working

That sounds exactly like what you're problem is.

Odds are either the bimetal spring has snapped or has detached from the cam. Give me a while to dig it out and I should be able to find the proper repair procedure for it - never been able to make much head or tail from it but I know I have it somewhere...

Can i go ahead take the choke cover off by the bolt in the centre or the three around the outside

Thanks very much mate

The three around the outside are the way to remove it from the main body - just scanning the docs now though if you can wait (pm me your email address)

Looking through the pages I sent you I think the most likely cause of the problem is that the spring has become detached from the cam in which case you just need to relocate it and tighten it all back up again!

Just remember to keep an eye on the markings on the housing so that it all goes back in the same position - it may not be relevant as the choke is not currently working and probably hasn't been set up in some time... at least it gives you a starting point.

Equally it could be that the housing has been rotated so far that the cam is permanently on its "hot" position in which case just rotating back might get you running again.