s1 fuel metering fuel pipe routes
Discussion
DONT stick a screwdriver down to check!
Start again! Disconnect all the pipes and remove the whole metering head complete with the air control valve. It is delicate so treat with care.
Check the air valve first. If the valve is in the incorrect place or sticking even the slightest bit, it will be impossible to set the fuel metering right. The air valve is moved solely by suction so it has to move freely. When it is out can you photo the position of the air valve at rest. The disc of the valve should be level with the top of the parallel section in the air tube. If it is up or down from that position the initial opening of the throttle will make the mixture way out. Too far down and it will massively overfuel and flood. Too far up and it will go massively weak and start cutting out, which will cause the valve to oscillate up and down, first very weak then very rich. (this can also be the cause of failure to run evenly at low speeds..the annoying 'hunting' in traffic)
The tube should be very clean. The air valve should move without any contact with the tube, a tiny bit of corrosion on the air valve plate or air tube could make a big difference. The air valve should be central in the tube with an equal space all round. If it has corroded or been forced that equal gap may be out. There should be no muck on the top of the air valve, a tiny amount will alter the weight and it wont react properly.
Make absolutely sure that, if you push the valve up, it returns to exactly the right place every time. If the position varies the pivot for the arm holding the valve could be corroded.
The whole thing MUST be completely clean and exact BEFORE messing with the fuel side or you are just chasing your tail.
DO NOT MESS WITH THE MIXTURE ADJUSTMENT SCREW UNTIL THE AIR VALVE IS RIGHT AND THE AIR DUCTS TO THE THROTTLE ARE PERFECT OR YOU WILL LOSE THE DATUM FROM WHICH TO MAKE FINE ADJUSTMENTS. People will keep adjusting this screw before thinking WHY it might need to be adjusted. Find the problem first!
Now check that, with the air valve in the correct place, it is in contact with the fuel meter plunger which you will see from underneath. If the plunger isnt coming down to the air flow meter's support arm it will overfuel at low throttle.
If the air meter plate wont come high enough check the 'mixture adjustment' screw has not already been screwed too far down. That screw adjusts the position of the arm NOT the flow of fuel. You HAVE to get the air valve in the right place in the air tube and the fuel metering plunger in contact with the air flow meter arm before you can get a basic setting from which to tune it.
From underneath you should be able to check that the fuel metering plunger will rise and fall OK with light finger pressure. If it does not then I am afraid it is an experts job to clean and reset the fuel metering side. And I know of only one firm which are set up to do it. And it aint cheap!
Check that far and come back, preferably with photos?
Start again! Disconnect all the pipes and remove the whole metering head complete with the air control valve. It is delicate so treat with care.
Check the air valve first. If the valve is in the incorrect place or sticking even the slightest bit, it will be impossible to set the fuel metering right. The air valve is moved solely by suction so it has to move freely. When it is out can you photo the position of the air valve at rest. The disc of the valve should be level with the top of the parallel section in the air tube. If it is up or down from that position the initial opening of the throttle will make the mixture way out. Too far down and it will massively overfuel and flood. Too far up and it will go massively weak and start cutting out, which will cause the valve to oscillate up and down, first very weak then very rich. (this can also be the cause of failure to run evenly at low speeds..the annoying 'hunting' in traffic)
The tube should be very clean. The air valve should move without any contact with the tube, a tiny bit of corrosion on the air valve plate or air tube could make a big difference. The air valve should be central in the tube with an equal space all round. If it has corroded or been forced that equal gap may be out. There should be no muck on the top of the air valve, a tiny amount will alter the weight and it wont react properly.
Make absolutely sure that, if you push the valve up, it returns to exactly the right place every time. If the position varies the pivot for the arm holding the valve could be corroded.
The whole thing MUST be completely clean and exact BEFORE messing with the fuel side or you are just chasing your tail.
DO NOT MESS WITH THE MIXTURE ADJUSTMENT SCREW UNTIL THE AIR VALVE IS RIGHT AND THE AIR DUCTS TO THE THROTTLE ARE PERFECT OR YOU WILL LOSE THE DATUM FROM WHICH TO MAKE FINE ADJUSTMENTS. People will keep adjusting this screw before thinking WHY it might need to be adjusted. Find the problem first!
Now check that, with the air valve in the correct place, it is in contact with the fuel meter plunger which you will see from underneath. If the plunger isnt coming down to the air flow meter's support arm it will overfuel at low throttle.
If the air meter plate wont come high enough check the 'mixture adjustment' screw has not already been screwed too far down. That screw adjusts the position of the arm NOT the flow of fuel. You HAVE to get the air valve in the right place in the air tube and the fuel metering plunger in contact with the air flow meter arm before you can get a basic setting from which to tune it.
From underneath you should be able to check that the fuel metering plunger will rise and fall OK with light finger pressure. If it does not then I am afraid it is an experts job to clean and reset the fuel metering side. And I know of only one firm which are set up to do it. And it aint cheap!
Check that far and come back, preferably with photos?
Ok so I've stripped the fuel metering head and there I think is my problem the piston is stuck solid rock solid . I suppose its easy to forget just how long this car has stood in the woods rusting and how delicate some parts are. I'm happy to have finally found what I am pretty sure is the problem and hopefully when relaced she will run proper and I can get on with painting it, Thanks for all the advice etc and hopefully this will be a closed paragraph lol.
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