correction: @jackwhoo did say had i considered bad float or cut off valve, but no one spoke of the gumming up of the valve. but thank you much jackwhoo for being so very close.OP here, as none of the replies although many helpful, seemed to nicely fit with the history and symptoms of the problem, i have been thinking about and checking what can be eliminated in the fuel system as a whole.
to cut out any doubts about everything up to fuel pump inlet i disconnected and put other end of pipe to pump into a can of E10 petrol. result problem still present. to begin with though engine would not start so took plugs out and the sooty insulators were soaking wet with petrol. turned engine over several times to blow the flooding out, steel bristle wire brushed the plugs and when all back together it started straight away, but as i say, still running very rough. seemingly then; caused by over fueling.
why so? well quite simple i concluded; float chamber cut-off valve was not stopping float chamber over filling. but why, and most importantly does the answer make sense when considering the temporary clearing of the problem after filling up with petrol mid trip as mentioned at start of the thread, and upon which no one here had come up with an answer that fitted the mid trip clearing. at least it may have been thought of, but no one posted their thoughts on it?
then i read the haynes manual thoroughly (theres a first time for everything..) and it did say that the float chamber should be cleaned out and the cut-off valve thoroughly cleaned and float level checked (bend arm if needed to correspond with measurement specified) it actually says that the cut-off valve can get gummed up. furthermore under routine maintenance section it says top of carb should be removed and chamber and cut-off valve thoroughly cleaned with carburetor cleaner - and get this: EVERY 24,000 MILES. big surprise to me; so frequently and even that it has to be done at all, what?
this is the only scenario that fits the history and symptoms of the problem. so when i next get a chance the top will come off and im sure i will find a gummed up float chamber and cut-off valve. meanwhile i am ordering up three sizes of rubber pipe to spec required for E10 petrol so all pipes including all the little vac ones can be renewed at the same time. will renew fuel filter too.
new question then: does the fuel tank accumulate sticky sediment too, only to be picked up after car has stood for a few days or more? that would also fit history of my problem nicely. assuming that does happen, how to clean out tank without taking it off the car? the routine maintenance doesnt say clean out tank every 24,000 miles
im now gonna start a new topic on a device in my Tipo Formula fuel system that does not appear in the haynes manual and the purpose of which remains a mystery to me. title: What is this fuel system 3 way device and does it go wrong?
if this thread stays dead, no matter, as i think it could be helpful as-is, for someone in the future.
cordiali saluti
so you go out to the parking lot, you get in your car and you drive real far, you drive through the night until you see a light, the light comes down and lands on the ground and out steps the man from mars.. rapture.. blondie :|
Technical weber carb mixture far too rich 1990 tipo 1.4 running very rough
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weber carb mixture far too rich 1990 tipo 1.4 running very rough
Re the flooding side , surely if that bad you would have smelt it and possibly seen stains and fuel around the carb, as well as the plug fouling you mentioned. Also a sooty tail pipe on exhaust.OP here, as none of the replies although many helpful, seemed to nicely fit with the history and symptoms of the problem, i have been thinking about and checking what can be eliminated in the fuel system as a whole.
to cut out any doubts about everything up to fuel pump inlet i disconnected and put other end of pipe to pump into a can of E10 petrol. result problem still present. to begin with though engine would not start so took plugs out and the sooty insulators were soaking wet with petrol. turned engine over several times to blow the flooding out, steel bristle wire brushed the plugs and when all back together it started straight away, but as i say, still running very rough. seemingly then; caused by over fueling.
why so? well quite simple i concluded; float chamber cut-off valve was not stopping float chamber over filling. but why, and most importantly does the answer make sense when considering the temporary clearing of the problem after filling up with petrol mid trip as mentioned at start of the thread, and upon which no one here had come up with an answer that fitted the mid trip clearing. at least it may have been thought of, but no one posted their thoughts on it?
then i read the haynes manual thoroughly (theres a first time for everything..) and it did say that the float chamber should be cleaned out and the cut-off valve thoroughly cleaned and float level checked (bend arm if needed to correspond with measurement specified) it actually says that the cut-off valve can get gummed up. furthermore under routine maintenance section it says top of carb should be removed and chamber and cut-off valve thoroughly cleaned with carburetor cleaner - and get this: EVERY 24,000 MILES. big surprise to me; so frequently and even that it has to be done at all, what?
this is the only scenario that fits the history and symptoms of the problem. so when i next get a chance the top will come off and im sure i will find a gummed up float chamber and cut-off valve. meanwhile i am ordering up three sizes of rubber pipe to spec required for E10 petrol so all pipes including all the little vac ones can be renewed at the same time. will renew fuel filter too.
new question then: does the fuel tank accumulate sticky sediment too, only to be picked up after car has stood for a few days or more? that would also fit history of my problem nicely. assuming that does happen, how to clean out tank without taking it off the car? the routine maintenance doesnt say clean out tank every 24,000 miles
im now gonna start a new topic on a device in my Tipo Formula fuel system that does not appear in the haynes manual and the purpose of which remains a mystery to me. title: What is this fuel system 3 way device and does it go wrong?
if this thread stays dead, no matter, as i think it could be helpful as-is, for someone in the future.
cordiali saluti
so you go out to the parking lot, you get in your car and you drive real far, you drive through the night until you see a light, the light comes down and lands on the ground and out steps the man from mars.. rapture.. blondie :|
By the way after cleaning carb completely including the needle jet on the float chamber I always put a bit of clean new hose on the carb inlet and blow through it then gradually turn the carb upside down , if needle jet working correctly it should then be impossible to blow through until you turn the car back upright, this way you will know it is working before refitting to the car.
Note if you just blow in the inlet pipe you will be tasting fuel for a long time afterwards , so not recommended.
There is a correct measurement for float height, but a quick guide a roughly the thickness of a BIC pen between float and cover when turned sideways.
I assume the three way device is to keep returning unused fuel back to tank as this helps keep the fuel cooler and less likely to vapourise.
