FINALLY found the true source of my "loss of power" problem...
I posted a couple-few weeks ago about my '82 Mazda 626 having intermittent issues with losing power under load - At that time, figured that the trouble was related to a dead or dying Alternator not putting enough juice to the battery, and therefore interfering with spark - Seemed to make sense, since when the alternator died and I put the new one in, the problem seemed to have vanished. Well, the good news is that it stayed gone for at least 3-4 weeks. The bad news is that it started showing up again last week - Symptoms same as ever: Hit the hill near Lakeside Market, and it starts chugging and lurching and bucking like it's right on the edge of being out of gas, even after just topping up the tank less than 10 minutes/10 miles back. Well, last night, it hit with a vengance... I hit the Lakeside hill at just under 45. Half a mile up, I was down to 30, and lurching and bucking like a rodeo bronco, with another mile or so to go before I hit flat land. Another couple hundred yards along, I was down to 15. 10 seconds later, I was dead on the side of the raod, and no amount of cranking would get it to start. Rolled it backwards to point the car downhill and coast back down to Lakeside Market where I could call a tow-truck. Got to the bottom of the hill, and out of sheer "Dammit, this thing SHOULD start!", I hit the key. It spun over instantly, humming along just as strong as it always has. OK, cancel the tow truck idea... Maybe I can get it home under its own power? Well, long story shorter, I did indeed manage to get it home, luurching and bucking like crazy every time I had to climb a hill, but somehow keeping it running. Flat or downhill stretches, it behaved just like normal - Namely, running strong. Uphill for more than a second or two? Chug, lurch, threaten to die. This sure sounds like a fuel issue, but everything I can check shows green and go. Problem has always been worst when travelling uphill forwards, with the occasional "on the flat" appearance when I was "getting on it" heavy for whatever reason. Could never duplicate the "dropouts" while standing still - It never happened with the car moving less than 20 MPH, which made it seriously difficult to try to troubleshoot. Part of the "shotgun" I fired at it was plugs, wires, rotor and cap - They were needed, at least according to the calendar (even though they looked fine to me when they got replaced) - That seemed to make a difference for a short time, but the problem returned. Couldn't find any vacuum leaks using the propane torch method. Fuel filter replaced multiple times. Fuel-pump test showed it was giving spec pressure, and a hair more than spec volume (Specced for 3-5 PSI, replace at 2.8PSI, Spec volume of 800+ ml per minute, replace fuel pump at 750 ml/min. Actual measured PSI: 4.1. Measured volume: 825 ml/minute) Compression is rock solid, at close enough to 150Kg/cm^2 on all four cylinders that my compression tester isn't sensitive enough to show me any variation (Spec: 135-180 Kg/cm^2, < 10% variance between highest and lowest cylinder) Finally, in desperation, today I lifted the top of the carb, going on the "It's acting like it's starving to death" hunch - I've eliminated everything else that makes even a tiny bit of sense, and diddled with a few things that shouldn't have anything to do with it. Got the carb open, and I'm measuring the float setting - It's a plastic float on a metal bracket, and it's so close to the book specs that I can't measure any error in the setting. But then I get to taking a closer look... The float rides on a "slides all the way through", free-floating pin - The pin is kept in place by the fact that once the top is screwed down, the area it sits in is too narrow to allow it to back out of the holes it goes through. That part is fine... What ISN'T fine is the no-longer-round holes in the float bracket! After dinking with the float adjustment a bit, I noticed that dropping the float didn't appear to open the needle valve. Started wondering about that, and got to looking closer at how the float was hung on the posts it attaches to, and that's when I noticed that the top of the holes in the bracket have worn to the point where they're no longer circular - They're very nearly twice as tall as they are wide! Pulled apart a spare carb I have for this beast, and found that its float had nice, tight, nearly perfectly round holes at that location. And when THAT float is moved up and down, there's a very clearly visible motion of the needle. Swapped floats, buttoned everything up, and took it for a test run. Sure enough - Absolutely no trace of the problem now. My "working theory": The worn holes were allowing the float to "sink" without actually tilting, which kept the needle from opening, and in turn, gave every sign of the car being out of gas. Hardly surprising, since for practical purposes, having the float bowl run dry is ideintical to having the gas tank empty. as for why it was intermittent, I'd say that the problem could only manifest when the vehicle was in certain positions (nose up versus nose down, ferinstance) so that when the float "fell" just right to bind slightly, it would function as intended, but when it got into another orientation, the "extra-large" holes would "un-bind" and let the pivot point fall, dropping the float without opening the valve. I'll be keeping an eye on the beast, but I'm pretty sure I've finally found the actual root problem - Damn, but it has taken long enough!!! -- Don Bruder - - New Email policy in effect as of Feb. 21, 2004. Short form: I'm trashing EVERY E-mail that doesn't contain a password in the subject unless it comes from a "whitelisted" (pre-approved by me) address. See <http://www.sonic.net/~dakidd/main/contact.html> for full details. |
Wow. Talk about tenacity. Good show, dude. I hope it works out
for you. "Don Bruder" > wrote in message ... > > I posted a couple-few weeks ago about my '82 Mazda 626 having > intermittent issues with losing power under load - At that > time, figured > that the trouble was related to a dead or dying Alternator not > putting > enough juice to the battery, and therefore interfering with > spark - > Seemed to make sense, since when the alternator died and I put > the new > one in, the problem seemed to have vanished. > > Well, the good news is that it stayed gone for at least 3-4 > weeks. The > bad news is that it started showing up again last week - > Symptoms same > as ever: Hit the hill near Lakeside Market, and it starts > chugging and > lurching and bucking like it's right on the edge of being out > of gas, > even after just topping up the tank less than 10 minutes/10 > miles back. > Well, last night, it hit with a vengance... I hit the Lakeside > hill at > just under 45. Half a mile up, I was down to 30, and lurching > and > bucking like a rodeo bronco, with another mile or so to go > before I hit > flat land. Another couple hundred yards along, I was down to > 15. 10 > seconds later, I was dead on the side of the raod, and no > amount of > cranking would get it to start. Rolled it backwards to point > the car > downhill and coast back down to Lakeside Market where I could > call a > tow-truck. Got to the bottom of the hill, and out of sheer > "Dammit, this > thing SHOULD start!", I hit the key. It spun over instantly, > humming > along just as strong as it always has. OK, cancel the tow truck > idea... > Maybe I can get it home under its own power? Well, long story > shorter, I > did indeed manage to get it home, luurching and bucking like > crazy every > time I had to climb a hill, but somehow keeping it running. > Flat or > downhill stretches, it behaved just like normal - Namely, > running > strong. Uphill for more than a second or two? Chug, lurch, > threaten to > die. This sure sounds like a fuel issue, but everything I can > check > shows green and go. > > Problem has always been worst when travelling uphill forwards, > with the > occasional "on the flat" appearance when I was "getting on it" > heavy for > whatever reason. Could never duplicate the "dropouts" while > standing > still - It never happened with the car moving less than 20 MPH, > which > made it seriously difficult to try to troubleshoot. Part of the > "shotgun" I fired at it was plugs, wires, rotor and cap - They > were > needed, at least according to the calendar (even though they > looked fine > to me when they got replaced) - That seemed to make a > difference for a > short time, but the problem returned. Couldn't find any vacuum > leaks > using the propane torch method. Fuel filter replaced multiple > times. > > Fuel-pump test showed it was giving spec pressure, and a hair > more than > spec volume (Specced for 3-5 PSI, replace at 2.8PSI, Spec > volume of 800+ > ml per minute, replace fuel pump at 750 ml/min. Actual measured > PSI: > 4.1. Measured volume: 825 ml/minute) > > Compression is rock solid, at close enough to 150Kg/cm^2 on all > four > cylinders that my compression tester isn't sensitive enough to > show me > any variation (Spec: 135-180 Kg/cm^2, < 10% variance between > highest and > lowest cylinder) > > Finally, in desperation, today I lifted the top of the carb, > going on > the "It's acting like it's starving to death" hunch - I've > eliminated > everything else that makes even a tiny bit of sense, and > diddled with a > few things that shouldn't have anything to do with it. > > Got the carb open, and I'm measuring the float setting - It's a > plastic > float on a metal bracket, and it's so close to the book specs > that I > can't measure any error in the setting. But then I get to > taking a > closer look... > > The float rides on a "slides all the way through", > free-floating pin - > The pin is kept in place by the fact that once the top is > screwed down, > the area it sits in is too narrow to allow it to back out of > the holes > it goes through. That part is fine... > > What ISN'T fine is the no-longer-round holes in the float > bracket! > After dinking with the float adjustment a bit, I noticed that > dropping > the float didn't appear to open the needle valve. Started > wondering > about that, and got to looking closer at how the float was hung > on the > posts it attaches to, and that's when I noticed that the top of > the > holes in the bracket have worn to the point where they're no > longer > circular - They're very nearly twice as tall as they are wide! > > Pulled apart a spare carb I have for this beast, and found that > its > float had nice, tight, nearly perfectly round holes at that > location. > And when THAT float is moved up and down, there's a very > clearly visible > motion of the needle. Swapped floats, buttoned everything up, > and took > it for a test run. Sure enough - Absolutely no trace of the > problem now. > > My "working theory": The worn holes were allowing the float to > "sink" > without actually tilting, which kept the needle from opening, > and in > turn, gave every sign of the car being out of gas. Hardly > surprising, > since for practical purposes, having the float bowl run dry is > ideintical to having the gas tank empty. as for why it was > intermittent, > I'd say that the problem could only manifest when the vehicle > was in > certain positions (nose up versus nose down, ferinstance) so > that when > the float "fell" just right to bind slightly, it would function > as > intended, but when it got into another orientation, the > "extra-large" > holes would "un-bind" and let the pivot point fall, dropping > the float > without opening the valve. > > I'll be keeping an eye on the beast, but I'm pretty sure I've > finally > found the actual root problem - Damn, but it has taken long > enough!!! > > -- > Don Bruder - - New Email policy in effect as > of Feb. 21, 2004. > Short form: I'm trashing EVERY E-mail that doesn't contain a > password in the > subject unless it comes from a "whitelisted" (pre-approved by > me) address. > See <http://www.sonic.net/~dakidd/main/contact.html> for full > details. |
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