I have noticed that after one particular long (8 mile) descent, one of my pinzies starts to sputter and missfire as soon as it hits flat ground again. It sounds as if one cylinder is not firing. It always does the same thing in the exact same spot! So far, it only has lasts a few miles before it purrs like a kitten again. Wierd!
I am running a new civi ignition and all the fluids and filters are fresh too. Any suggestions?
Sputtering/missfiring after long descents. ?
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Twin Pinzies
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Twin Pinzies
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Is the vacuum/mainfold a common problem? Where do I look? I pulled my plugs (good condition and spark), checked the dist. cap/rotor, and it still stumbled and sounded like it wasn't firing on all cylinders still. I drove it anyway and after forcing it for few miles, it was running perfectly again! ?
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lindenengineering
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Here are a few pointers.
Check your manifold depression at idle, it should be 15 inches of Hg but where you are it may be as low as 12hg min. Anything lower than this will indicate if you have a manifold leak at (brake vacuum take off, manifold balance hose or cracked manifold(s). You can connect the gauge up to the stub port sucking the diz into a partial vacuum.
Now to the actual condition on the trail. Judging from what you are posting you have just completed a steep downhill decent with your foot off the gas. VIZ:-
High vacuum manifold condition, long decent - no gas pedal application, maybe some brake. ( that high HG reading should exist unless you have vacuum problems as listed in the previous paragraph.)
Conditions such as have a tendency to cause the carburetor bowl(s) level(s)to be drawn down. In theory/ideal conditions, the fuel pump should keep those bowls at the design level for instant response when you apply the accelerator pedal and call for power. Should the bowl(s) be low due to a feed problem/bowl level problem especially when at an extreme angle there may be insufficent fuel for the accelerator pumps and jet supply, hence the splutter.
Now don't jump to conclusions yet. Should you have a partial flood condition the cylinders affected may be getting an overdose of fuel, this will be discharged into the exhaust system causing a very dense hydrocarbon environment but with insufficient oxygen to support combustion. When you plonk your foot on the gas pedal this will for a period increase that density until it clears; Causing again a splutter until the cylinder/exhaust is cleared. With this condition there is usually a series of exhaust explosion retorts as oxygen is introduced by slugs of burning gases from the cylinders as better combustion returns. You may even notice an increase in exhaust stink though Pinzies and pre 1971 vehicles all do this (no pollution controls see)
So with all this info try to establish which condition actually exists and go from there to determine the actual cause of the fault.
Dennis
Linden Engineering Inc
Check your manifold depression at idle, it should be 15 inches of Hg but where you are it may be as low as 12hg min. Anything lower than this will indicate if you have a manifold leak at (brake vacuum take off, manifold balance hose or cracked manifold(s). You can connect the gauge up to the stub port sucking the diz into a partial vacuum.
Now to the actual condition on the trail. Judging from what you are posting you have just completed a steep downhill decent with your foot off the gas. VIZ:-
High vacuum manifold condition, long decent - no gas pedal application, maybe some brake. ( that high HG reading should exist unless you have vacuum problems as listed in the previous paragraph.)
Conditions such as have a tendency to cause the carburetor bowl(s) level(s)to be drawn down. In theory/ideal conditions, the fuel pump should keep those bowls at the design level for instant response when you apply the accelerator pedal and call for power. Should the bowl(s) be low due to a feed problem/bowl level problem especially when at an extreme angle there may be insufficent fuel for the accelerator pumps and jet supply, hence the splutter.
Now don't jump to conclusions yet. Should you have a partial flood condition the cylinders affected may be getting an overdose of fuel, this will be discharged into the exhaust system causing a very dense hydrocarbon environment but with insufficient oxygen to support combustion. When you plonk your foot on the gas pedal this will for a period increase that density until it clears; Causing again a splutter until the cylinder/exhaust is cleared. With this condition there is usually a series of exhaust explosion retorts as oxygen is introduced by slugs of burning gases from the cylinders as better combustion returns. You may even notice an increase in exhaust stink though Pinzies and pre 1971 vehicles all do this (no pollution controls see)
So with all this info try to establish which condition actually exists and go from there to determine the actual cause of the fault.
Dennis
Linden Engineering Inc
OOOps no customer bashing now
Dennis,
I could never put things so eloquently as you but I have been thinking about this post since it was first posted, it reminds me of my early motorcycle days. I remember that back in the 70's I was riding a Ducati 250 single, no unfortunately not the one with desmodromic valves but the MK111, of course it had a megaphone type silencer and was pretty quick for the times. One of the pleasures of driving it was the aural pleasures that it bestowed. Not only from the unmistakable sound of a single under throttle but also from rolling off the throttle and snicking down the box at high speed when peeling into bends, using engine compression to assist in scrubbing off speed. This produced the most glorious sounds twitter, twitter with the occasional explosion in the megaphone followed by larger explosions as the throttle was snapped open when just hitting the apex.
My brother who occasionaly followed me often reported that licks of flame shot out the back of my exhaust which helped to encourage him to keep a respectful distance from the flame thrower. I was only aware of the flames at night of course and long distances after sunset where necessarily short, about the length of time it took for the battery to run down when using the lights from lack of charging due to poor Italian auto electronics.
I think that I can remember a slight hesitancy for initial pick up which would have been due I thought to temporary weakness. I do remember playing around with carburetor jets trying to eliminate some of the attention of PC Plod who was less enamored than I was with my version of the dawn chorus. I can attest that the explosions were due to unburnt fuel in the exhaust but found some of the twitter was down to exhaust leakage due to poor sealing of the various exhaust joints. This was often awkward to put right I remember because as the blued down pipes were extremely hot as they were only single skinned in those days so playing around with them after a run was not fun and waiting to do this while cold often of course was more of a hit and miss a fare.
Essentially some cabs of the period were relatively crude and so an engine set up for smooth running may not perform to its maximum or compensate for temporary conditions and the contrary may be also be so. Compromised adjustment was often the order. I understood at that time that the unburnt fuel was down to the fact that the engine was temporarily outside of its optimum operating fuel range and hence no combustion in the cylinder but put this down to fuel weakness rather than being too rich. However this was a long time ago.
Anthony
I could never put things so eloquently as you but I have been thinking about this post since it was first posted, it reminds me of my early motorcycle days. I remember that back in the 70's I was riding a Ducati 250 single, no unfortunately not the one with desmodromic valves but the MK111, of course it had a megaphone type silencer and was pretty quick for the times. One of the pleasures of driving it was the aural pleasures that it bestowed. Not only from the unmistakable sound of a single under throttle but also from rolling off the throttle and snicking down the box at high speed when peeling into bends, using engine compression to assist in scrubbing off speed. This produced the most glorious sounds twitter, twitter with the occasional explosion in the megaphone followed by larger explosions as the throttle was snapped open when just hitting the apex.
My brother who occasionaly followed me often reported that licks of flame shot out the back of my exhaust which helped to encourage him to keep a respectful distance from the flame thrower. I was only aware of the flames at night of course and long distances after sunset where necessarily short, about the length of time it took for the battery to run down when using the lights from lack of charging due to poor Italian auto electronics.
I think that I can remember a slight hesitancy for initial pick up which would have been due I thought to temporary weakness. I do remember playing around with carburetor jets trying to eliminate some of the attention of PC Plod who was less enamored than I was with my version of the dawn chorus. I can attest that the explosions were due to unburnt fuel in the exhaust but found some of the twitter was down to exhaust leakage due to poor sealing of the various exhaust joints. This was often awkward to put right I remember because as the blued down pipes were extremely hot as they were only single skinned in those days so playing around with them after a run was not fun and waiting to do this while cold often of course was more of a hit and miss a fare.
Essentially some cabs of the period were relatively crude and so an engine set up for smooth running may not perform to its maximum or compensate for temporary conditions and the contrary may be also be so. Compromised adjustment was often the order. I understood at that time that the unburnt fuel was down to the fact that the engine was temporarily outside of its optimum operating fuel range and hence no combustion in the cylinder but put this down to fuel weakness rather than being too rich. However this was a long time ago.
Anthony
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Twin Pinzies
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lindenengineering
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Twin Pinzies
What's mind boggling, carb cleaner or the internal combustion engine?
If you are non technical then I suppose it might be.
As for carb cleaner, yes that stuff is quite remarkable and we use it alot to clear out inlet tracts. MAF sensors, gums/deposits in cylinders, watch o2 sensors come to life and read cat reactions when some appeared to be blocked up.
A goodly dose down the throats of a hot Pinz can do wonders as will a dose of Seafoam (get two-one for each carb=2 cylinders). I tend to use a more expensive product for lux cars from Kenz & Leslie but Seafoam is about $5 a can form Napa and should appeal to the cheap and cheerful amongst you. Follow the instructions to the letter and don't dump the whole bloody lot down the throat in one go, drizzle it in with about 2K revs on board.
You should do this if you have a carboned up engine that needs a clean out and is running on (dieseling). Beware do it where the neighbours don't have a hizzie fit, you will create clouds of smoke.
There you are mate a cheap fix in a can that can work----Sometimes--Before you have to get down and dirty.
Dennis
What's mind boggling, carb cleaner or the internal combustion engine?
If you are non technical then I suppose it might be.
As for carb cleaner, yes that stuff is quite remarkable and we use it alot to clear out inlet tracts. MAF sensors, gums/deposits in cylinders, watch o2 sensors come to life and read cat reactions when some appeared to be blocked up.
A goodly dose down the throats of a hot Pinz can do wonders as will a dose of Seafoam (get two-one for each carb=2 cylinders). I tend to use a more expensive product for lux cars from Kenz & Leslie but Seafoam is about $5 a can form Napa and should appeal to the cheap and cheerful amongst you. Follow the instructions to the letter and don't dump the whole bloody lot down the throat in one go, drizzle it in with about 2K revs on board.
You should do this if you have a carboned up engine that needs a clean out and is running on (dieseling). Beware do it where the neighbours don't have a hizzie fit, you will create clouds of smoke.
There you are mate a cheap fix in a can that can work----Sometimes--Before you have to get down and dirty.
Dennis
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Twin Pinzies
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lindenengineering
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Water in the cyls can have some dire consequences.
I have never been the fan of this practice after a mechanic I apprenticed under in the 1960's (showing my age now!) put just a bit tooo much down (or in this case up the throat) of a splendid 1936 8 HP Morris Touring Car he received from his late aunt's estate.
Doing a carbon clean out with an excess of that popular liquid locked the engine up at 2000ish r/m, bust a rod, broke off half a main bearing cap that all got blown out the side of the block all in about a millisecond flat.
The engine on that car was unique having a thermo syphon cooling system and the nearest replacement was from a 1948 Minor but it had a water pump that made the old gal look like an amorphodite when you lifted the bonnet (hood). Dropped the price/value of the vehicle as well.
Shame, I liked driving that chugga bug and as a teen I remember it being a great chic magnet but lacked the room in the back seat to get your "leg over".
Dennis
I have never been the fan of this practice after a mechanic I apprenticed under in the 1960's (showing my age now!) put just a bit tooo much down (or in this case up the throat) of a splendid 1936 8 HP Morris Touring Car he received from his late aunt's estate.
Doing a carbon clean out with an excess of that popular liquid locked the engine up at 2000ish r/m, bust a rod, broke off half a main bearing cap that all got blown out the side of the block all in about a millisecond flat.
The engine on that car was unique having a thermo syphon cooling system and the nearest replacement was from a 1948 Minor but it had a water pump that made the old gal look like an amorphodite when you lifted the bonnet (hood). Dropped the price/value of the vehicle as well.
Shame, I liked driving that chugga bug and as a teen I remember it being a great chic magnet but lacked the room in the back seat to get your "leg over".
Dennis
OOOps no customer bashing now
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william curry
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I can not imagine the idiot that would put enough water down the carb to do that much damage. The practice of dribbling water down the carb was done by a local tune up shop. My friends who worked there moved to ... you guessed it Colorado. I don't know if they still use that method but they are still doing mechanical work.
Mike
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lindenengineering
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