Systematic Breakdown Troubleshooting
Posted: Wed Sep 26, 2012 1:08 pm
***
It is ironic just last night I added to a thread about systematic troubleshooting and this morning I had a breakdown of my own requiring troubleshooting skills that turned a bad morning into a better morning in less than 10 minutes.
Being a firm believer in preventative maintenance, it really annoys me to have a breakdown as I spend a lot of time and money, (when I have both), to make sure breakdowns are avoided on everything I own to the best of my ability.
I'd rather work on the tractor when its warm and there is no snow on the ground or after the grass has been cut vs. standing outside in a blizzard wondering why it died or looking at 12 inches of grass wondering why it won't start.
Today I was bringing my plow cub up front for winter service. Its used for towing things around during the summer so it has been run recently.
I have noticed in the past a very occasional brief ignition cut out or complete miss every once in a while, nothing long enough to stall it, just a very brief skip every now and then... Stuff that a tune up and other basic maintenance procedures could never seem to rid the cub of, but it has been doing it for a while, maybe every third or forth use.
This morning it cut out, stalled and wouldn't re start. I thankfully was able to coast it down hill into my front garage for shelter from the rain that started just after it died.
I have a system I follow to systematic trouble shoot breakdowns. Fuel, Air, Compression, Spark or F. A. C. S. is what I teach people to remember to get them on the right track when trouble shooting a breakdown... Just like human life, Airway, Breathing, and Circulation. The A. B. C.'s of life, picked up years ago and never forgotten.
Fuel... I had about half a tank and the shut off was open, should have gas to the carb at least. At this point I was pretty satisfied the carb was not the issue as it shut off like it was turned off and not starved for fuel.
I moved on to the air. Choke was open, the lever wasn't slipped on the shaft, nothing should be prohibiting it from breathing and it was breathing well before it stopped.
Onto compression. The engine was running well and as I cranked it, it sounded the way you would expect a normal engine with compression to sound when cranked. Again, it was running well so for now I will move along to spark.
Spark. This has to be it. All my other systems at this point seem to be a go.
Removed a plug wire, no spark. Check for spark from the coil wire no spark. Checked to make sure the ignition switch was on, it was, wiggled it, still cranks with no spark. This is where a lot of people get off track (and I'm sure glad I didn't this morning) and take off the distributor cap and start messing with the points and rotor.
I next grabbed a test light to check both low voltage connections on the coil.
The terminal with the short wire to the distributor should blink the test light when the engine is cranked with the ignition on as the points open and close and the other terminal should light the test light with constant voltage from the ignition switch.
Since the distributor wire to the coil is easiest to reach I checked that first. Nothing, no light. Could be the points not operating properly? Checked the other terminal. Nothing here either. No power from the ignition switch. This is why the other coil terminal is dead, there has to be power from the ignition switch which there seems to be none.
Slipped some vacuum hose over all but the very tip of my ice pick style test light to prevent shorting things out behind the dash and found power to the ignition switch and power to the wire that runs to the coil when the switch is pulled out.
About have it solved now but why isn't the power getting to the coil?
I started un-taping the original wiring harness with the ignition, voltage regulator, and headlight wires. This cub has the original wiring harness which had been wrapped with electrical tape by the prev owner.
I proceeded to find something I had missed during my maintenance inspections.
Behind the rockshaft which also has a boomerang bolted to it, was a very short section of harness that had been rubbing the back of the rockshaft right at the edge of a metal harness retainer clip.
The ignition wire was the outer wire in the bundle so it took the beating and this morning took its last rub before being rubbed through.
Since the PO had wrapped the harness with electrical tape it made the chafed area dark and the rockshaft with larger boomerang hid it from plain sight. Had it been the headlight wire, not as much of a problem. But had it been a voltage regulator/headlight switch wire, this would have made for some interesting charging system problems.
Experienced mechanics probably won't have read down this far but I am targeting the guys who are still learning or want to improve their troubleshooting skills so if you're still with me good.
Please take 3 educational things away from this post.
First, signs of trouble seldom cure themselves. Something was making that tractor cut out all along and I knew it. I just didn't spend enough time looking for the culprit because the cub ran like a watch 99% of the time.
Second and most important. Be very systematic when you trouble shoot. In the case of a poor running engine, yes there can be several issues keeping it from running like a watch. But when it comes to a tractor stopping dead in its tracks, 99.9999% of the time there is only 1 thing that caused the break down.
As you can see, too many times a breakdown like I experienced this morning turns into a real bad experience because a troubleshooting system wasn't followed through. Getting ahead of things such as ripping into the distributor wouldn't have solved a thing but added a potential starting issue once the actual problem was detected.
It took less than 10 min to locate the open wire, crimp and heat shrink and wrap the repair and get back to what I was doing so I had time to type this!
The third thing to remember is always go back to the last thing you messed with in case of failure!
If you just treated the distributor to new points, codenser, cap and a rotor, it runs briefly and stops, even though you are 100% sure it sounded like it ran out of gas or the carb clogged up, it is almost 100% guaranteed the last thing you messed with caused the problem you have now, like the points slipped or the condenser wire grounded out.
If you start tampering with more than one system at a time or fail to completely follow through trouble shooting in a systematic manner, you are asking for a headache and will have a tractor on your hands that you will likely never get started without help.
Comments, suggestions?
It is ironic just last night I added to a thread about systematic troubleshooting and this morning I had a breakdown of my own requiring troubleshooting skills that turned a bad morning into a better morning in less than 10 minutes.
Being a firm believer in preventative maintenance, it really annoys me to have a breakdown as I spend a lot of time and money, (when I have both), to make sure breakdowns are avoided on everything I own to the best of my ability.
I'd rather work on the tractor when its warm and there is no snow on the ground or after the grass has been cut vs. standing outside in a blizzard wondering why it died or looking at 12 inches of grass wondering why it won't start.
Today I was bringing my plow cub up front for winter service. Its used for towing things around during the summer so it has been run recently.
I have noticed in the past a very occasional brief ignition cut out or complete miss every once in a while, nothing long enough to stall it, just a very brief skip every now and then... Stuff that a tune up and other basic maintenance procedures could never seem to rid the cub of, but it has been doing it for a while, maybe every third or forth use.
This morning it cut out, stalled and wouldn't re start. I thankfully was able to coast it down hill into my front garage for shelter from the rain that started just after it died.
I have a system I follow to systematic trouble shoot breakdowns. Fuel, Air, Compression, Spark or F. A. C. S. is what I teach people to remember to get them on the right track when trouble shooting a breakdown... Just like human life, Airway, Breathing, and Circulation. The A. B. C.'s of life, picked up years ago and never forgotten.
Fuel... I had about half a tank and the shut off was open, should have gas to the carb at least. At this point I was pretty satisfied the carb was not the issue as it shut off like it was turned off and not starved for fuel.
I moved on to the air. Choke was open, the lever wasn't slipped on the shaft, nothing should be prohibiting it from breathing and it was breathing well before it stopped.
Onto compression. The engine was running well and as I cranked it, it sounded the way you would expect a normal engine with compression to sound when cranked. Again, it was running well so for now I will move along to spark.
Spark. This has to be it. All my other systems at this point seem to be a go.
Removed a plug wire, no spark. Check for spark from the coil wire no spark. Checked to make sure the ignition switch was on, it was, wiggled it, still cranks with no spark. This is where a lot of people get off track (and I'm sure glad I didn't this morning) and take off the distributor cap and start messing with the points and rotor.
I next grabbed a test light to check both low voltage connections on the coil.
The terminal with the short wire to the distributor should blink the test light when the engine is cranked with the ignition on as the points open and close and the other terminal should light the test light with constant voltage from the ignition switch.
Since the distributor wire to the coil is easiest to reach I checked that first. Nothing, no light. Could be the points not operating properly? Checked the other terminal. Nothing here either. No power from the ignition switch. This is why the other coil terminal is dead, there has to be power from the ignition switch which there seems to be none.
Slipped some vacuum hose over all but the very tip of my ice pick style test light to prevent shorting things out behind the dash and found power to the ignition switch and power to the wire that runs to the coil when the switch is pulled out.
About have it solved now but why isn't the power getting to the coil?
I started un-taping the original wiring harness with the ignition, voltage regulator, and headlight wires. This cub has the original wiring harness which had been wrapped with electrical tape by the prev owner.
I proceeded to find something I had missed during my maintenance inspections.
Behind the rockshaft which also has a boomerang bolted to it, was a very short section of harness that had been rubbing the back of the rockshaft right at the edge of a metal harness retainer clip.
The ignition wire was the outer wire in the bundle so it took the beating and this morning took its last rub before being rubbed through.
Since the PO had wrapped the harness with electrical tape it made the chafed area dark and the rockshaft with larger boomerang hid it from plain sight. Had it been the headlight wire, not as much of a problem. But had it been a voltage regulator/headlight switch wire, this would have made for some interesting charging system problems.
Experienced mechanics probably won't have read down this far but I am targeting the guys who are still learning or want to improve their troubleshooting skills so if you're still with me good.
Please take 3 educational things away from this post.
First, signs of trouble seldom cure themselves. Something was making that tractor cut out all along and I knew it. I just didn't spend enough time looking for the culprit because the cub ran like a watch 99% of the time.
Second and most important. Be very systematic when you trouble shoot. In the case of a poor running engine, yes there can be several issues keeping it from running like a watch. But when it comes to a tractor stopping dead in its tracks, 99.9999% of the time there is only 1 thing that caused the break down.
As you can see, too many times a breakdown like I experienced this morning turns into a real bad experience because a troubleshooting system wasn't followed through. Getting ahead of things such as ripping into the distributor wouldn't have solved a thing but added a potential starting issue once the actual problem was detected.
It took less than 10 min to locate the open wire, crimp and heat shrink and wrap the repair and get back to what I was doing so I had time to type this!
The third thing to remember is always go back to the last thing you messed with in case of failure!
If you just treated the distributor to new points, codenser, cap and a rotor, it runs briefly and stops, even though you are 100% sure it sounded like it ran out of gas or the carb clogged up, it is almost 100% guaranteed the last thing you messed with caused the problem you have now, like the points slipped or the condenser wire grounded out.
If you start tampering with more than one system at a time or fail to completely follow through trouble shooting in a systematic manner, you are asking for a headache and will have a tractor on your hands that you will likely never get started without help.
Comments, suggestions?