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malcolm
& Clementine the Cat
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Hi damir,
Carburettors do not go out of adjustment, so should not need adjusting unless they have been fiddled with in the past. Adjusting the carburettor should be your last resort.
The first step would be to service the engine, ensuring that the distributor parts are in good condition. An engine that has not been serviced regularly will run badly and have excessive fuel consumption.
Next, check that all of the pipes and hoses are still connected to the carburettor and check there are no holes in the hoses. You might need to unscrew the air filter cover and the air filter base to view the carburettor.
Then remove the air filter and look at the top of the carburettor. Make sure the flap at the top (the choke valve) is fully open when the choke is pushed fully in. Otherwise the choke cable will need adjusting.
Finally, if none of these things have helped, and you suspect someone has messed around with the carburettor in the past then you might want to check the mixture setting. There is a screw with a spring around it on the body of the carburettor facing the inner wing. Screw this fully in, then screw it out by 1.5 turns. That should give about the right mixture setting.
Let us know how you get on.
Carburettors do not go out of adjustment, so should not need adjusting unless they have been fiddled with in the past. Adjusting the carburettor should be your last resort.
The first step would be to service the engine, ensuring that the distributor parts are in good condition. An engine that has not been serviced regularly will run badly and have excessive fuel consumption.
Next, check that all of the pipes and hoses are still connected to the carburettor and check there are no holes in the hoses. You might need to unscrew the air filter cover and the air filter base to view the carburettor.
Then remove the air filter and look at the top of the carburettor. Make sure the flap at the top (the choke valve) is fully open when the choke is pushed fully in. Otherwise the choke cable will need adjusting.
Finally, if none of these things have helped, and you suspect someone has messed around with the carburettor in the past then you might want to check the mixture setting. There is a screw with a spring around it on the body of the carburettor facing the inner wing. Screw this fully in, then screw it out by 1.5 turns. That should give about the right mixture setting.
Let us know how you get on.
Steve Hennessey
Moderator
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Clementine, your reply goes through the basics of diagnosing high fuel consumption, and you also quite rightly said that carbs do not go out of adjustment. However, there are two ways of approaching this. A brand new carb will stay in adjustment for a long period of time, but when certain components wear, such as the butterfly spindle for example, a tweak on the mixture screw will solve the problem as it would be impractical to replace this component every time the CO fell by a small %. Similarly, as the valve seats erode over time and there is some leak by, a carb adjustment will sort the problem rather than removing the head and doing a valve job. With any car, you are going to get wear from day one and adjustments will be needed.
I also think that contributors need to let us know the type of carb fitted to their engines and the capacity of their engine. It would also be helpful to know which make of distributor is fitted as there were 3 different makes used.
High fuel consumption can also be attributed to problems with the distributor. Seized balance weights and a faulty vacuum unit will almost definitely cause the wallet to be emptied faster than expected :cry:
Damir, what is your current fuel consumption (preferably in miles per gallon)?
Steve
I also think that contributors need to let us know the type of carb fitted to their engines and the capacity of their engine. It would also be helpful to know which make of distributor is fitted as there were 3 different makes used.
High fuel consumption can also be attributed to problems with the distributor. Seized balance weights and a faulty vacuum unit will almost definitely cause the wallet to be emptied faster than expected :cry:
Damir, what is your current fuel consumption (preferably in miles per gallon)?
Steve
I was interested to see the thread on carby tuning. I have an 845 cc '68 model which orignally would have had a zenith 28IF or small solex, currently its got a rebuilt 28IF out of a GTL, which has notionally the same jet settings.
What I find is trying to tune the mixture setting (i.e. set until hunting is at a minimum) is well nigh impossible. The later manuals give up all pretence of that and say to set to the best result on an exhaust gas analyser.
Does anyone have any experiences they want to share about the solex carbs with accelerator pumps that were fitted on some mid 70's R4s? Were these appreciably better? Were they fitted on any other cars? What about modern carbs? Any current model small cars out there got a candidate for conversion? (I'm thinking of Jap or Korean 3 cylinder things) Anyone tried this? I've heard of people using small webers from fiat 850's etc but haven't heard whether they were any good or not.
What I find is trying to tune the mixture setting (i.e. set until hunting is at a minimum) is well nigh impossible. The later manuals give up all pretence of that and say to set to the best result on an exhaust gas analyser.
Does anyone have any experiences they want to share about the solex carbs with accelerator pumps that were fitted on some mid 70's R4s? Were these appreciably better? Were they fitted on any other cars? What about modern carbs? Any current model small cars out there got a candidate for conversion? (I'm thinking of Jap or Korean 3 cylinder things) Anyone tried this? I've heard of people using small webers from fiat 850's etc but haven't heard whether they were any good or not.
Steve Hennessey
Moderator
- Messages
- 1,406
Pieter, the 28IF is a very basic carb and you don't need an analyser to set the mixture. I use a tachometer and turn the mixture screw until the optimum revs are achieved. If you try this method and the car still does run right, you may have problems with the engine. Check all compressions, condition of distributor components, manifold gasket and the gasket between the carb and the manifold. If all these are OK, the carb itself is playing up.
It would be best to use a pumped carb corrrectly jetted for your engine. In my honest opinion, all 28IF carbs should be thrown in the bin!
You could experiment with other carbs, but it would be better to use the correct one for the car. As to using a carb from a later car, I don't think any modern cars use carbs now - but correct me if I'm wrong.
Steve
It would be best to use a pumped carb corrrectly jetted for your engine. In my honest opinion, all 28IF carbs should be thrown in the bin!
You could experiment with other carbs, but it would be better to use the correct one for the car. As to using a carb from a later car, I don't think any modern cars use carbs now - but correct me if I'm wrong.
Steve
Liam4R4SPARES
Enthusiast
- Messages
- 208
After my car not meeting the MOT emmision limits and using excess fuel i attempted to adjust the carb to weaken the mixture . No matter how far in i screwed the mixture screw in nothing happened.Thinking like most people the carb was shot i replaced it with a low mileague example but this made no difference.To cut a longer story short the small breather pipe from the inlet manifold to the carb has a very small removable restriction valve in it that becomes blocked over time thus reducing air to the carb giving a too rich mixture. Just remove the valve give it a clean with a pin or something and simple refit and recheck mixture.
On the carburetor there are two screws with springs ,one on the left and one on the right , what is the setting for each one ,the left is 1.5 turns to the left from closed , what is the setting for the one on the right , mine started fine yesterday but now it won't fire
Geoff in the Gully
Getting it together
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- 281
One screw adjusts the air-fuel mix when idling. The other controls the idling speed.
Neither has any effect of mixture ratio when the engine is running (not idling) AFAIK.
Overly rich mix could be a problem with the float in the carby - too high a fuel level - or worn / enlarged jets.
Since you changed the carby, I doubt though whether either of those issues are a factor.
Neither has any effect of mixture ratio when the engine is running (not idling) AFAIK.
Overly rich mix could be a problem with the float in the carby - too high a fuel level - or worn / enlarged jets.
Since you changed the carby, I doubt though whether either of those issues are a factor.
Azazello
habitué
- Messages
- 1,109
- Location
- Italy
My 75 export runs on 32 solex, and works quite fine.
My 81 f4 (billancourt engine too, both 845 cc) has a zenith 28 which I found quite difficult to set... dismounting it showed a worn butterfly, so I changed the carb base with one from a later 956 and now works fine.
I have in my basement a couple of dell'orto carbs... are they any better? Anybody knows them and could tell me if they will improve something and it's worth the effort in cleaning and refurbishing gaskets and so on?
My 81 f4 (billancourt engine too, both 845 cc) has a zenith 28 which I found quite difficult to set... dismounting it showed a worn butterfly, so I changed the carb base with one from a later 956 and now works fine.
I have in my basement a couple of dell'orto carbs... are they any better? Anybody knows them and could tell me if they will improve something and it's worth the effort in cleaning and refurbishing gaskets and so on?
Maybe not exactly the answer required for this thread but I have recently had quite a few problems with fuel related issues.
A cascade of events led me to do a full diagnosis, initial finding, water in fuel, not good, full tank wasted, carb cleaned out and tried to get running good, gasket torn presumably letting air in carb, new gasket, all okay for a week then same problem.
Finally by accident split air pipe from rocker cover to carb found, so as in previous advice in this thread it is wise to check all options including air pipes, no more headaches! .......For now !