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656 voltage problems


new1206
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I'm working on my neighbor's 656 gas that is loosing spark and voltage is all over the map. It will be running along fine, then out of the blue will just die. When i check for spark after it dies there is nothing. Changed the coil thinking that was the problem but that didn't help. After a few minutes it seems to come back to life and starts again. 

Along with this problem when I put my multimeter on the battery the voltage jumps around all over the place, from 2 volts to 14. Thought the voltage regulator was gone in the alternator so I changed out the alternator and this didn't help. I cleaned up the ground cable where it is attached to the tractor, that didn't seem to help either.  Does anyone think the stalling problem and the voltage problem are connected? If so where show I start looking?

Any help on this would be appreciated. Thanks

 

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Has battery been load tested?  Most 656 tractors had an external regulator. If things check out, try using a jumper wire from battery positive post to the coil positive terminal. Be aware that the key will NOT shut it down

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2 minutes ago, mrfred54 said:

Has battery been load tested?  Most 656 tractors had an external regulator. If things check out, try using a jumper wire from battery positive post to the coil positive terminal. Be aware that the key will NOT shut it down

On second thought, the key may shut it down if the carburetor solenoid is work in properly

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10 hours ago, new1206 said:

If so where show I start looking?

First thing I would look for is another DVOM.  If you are getting battery voltage readings of 2 volts on a battery that will start the tractor, your meter is junk, or the meter has a bad connection.  

If I was working on it, I would be looking the ignition switch and associated wiring over really good..... 

Is he paying for the alternator and the coil? 

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18 hours ago, new1206 said:

I'm working on my neighbor's 656 gas that is loosing spark and voltage is all over the map. It will be running along fine, then out of the blue will just die. When i check for spark after it dies there is nothing. Changed the coil thinking that was the problem but that didn't help. After a few minutes it seems to come back to life and starts again. 

Along with this problem when I put my multimeter on the battery the voltage jumps around all over the place, from 2 volts to 14. Thought the voltage regulator was gone in the alternator so I changed out the alternator and this didn't help. I cleaned up the ground cable where it is attached to the tractor, that didn't seem to help either.  Does anyone think the stalling problem and the voltage problem are connected? If so where show I start looking?

Any help on this would be appreciated. Thanks

 

Make sure you have right coil. Then if it has electronic ign replace it. If not replace condenser clean and grease the points. Being you say it loses spark. If it does it again hot wire from starter sol to positive side of coil see if it starts. A 656 could have a porcelain resistor in coil wire.

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8 hours ago, J-Mech said:

First thing I would look for is another DVOM.  If you are getting battery voltage readings of 2 volts on a battery that will start the tractor, your meter is junk, or the

meter has bad connection

Just what I thought. One of the test leads in mine got a "crimp" in it once and that is exactly how it would read, jump all over the place.

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Make sure you are testing on the actual battery posts, not on the cable clamps.   A bad connection ot the batttery can do that.

If you are, then either the battery has a bad internal connection,  which I would expect to see as a no start problem) or your meter is has got issues.  A bar alternator will not make a good battery bounce that much--the battery stabilizes the voltage.

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Tried the multimeter on a pickup and seems to stay steady at 14.2. I don't think it's the meter. cleaned the connections on the starter and battery that didn't seem to help either and it does start as long as there is spark. 

 

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I'm working on my neighbor's 656 gas that is loosing spark and voltage is all over the map. It will be running along fine, then out of the blue will just die. When i check for spark after it dies there is nothing. Changed the coil thinking that was the problem but that didn't help. After a few minutes it seems to come back to life and starts again. 

 

So when it dies you need to check for 12V at the coil primary, if nothing then your problem most likely is has something to do with the key switch or carb solenoid ( if it has one)  .   Start from the voltage source (battery) through the switch to the coil. There must be a loose connection or something. I had an issue with my 450 once where the crimp connector on the wire from the voltage regulator to the key switch came loose. Periodically it would as you say just die out of the blue, because it was the same as turning the key switch off. No spark is an open circuit somewhere and replacing parts isn't fixing it so its not the parts.

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Mechanical voltage regulators work by switching between maximum charging and no charging. They react much slower than transistor regulators and as a result sometimes do not play well with digital VOMs. Analog meters cannot react quick enough the show the changes in voltage so the resulting reading shows a steady reading. Your digital meter is constantly displaying the voltage it sees when it refreshes the display.

 

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39 minutes ago, Owen Aaland said:

Mechanical voltage regulators work by switching between maximum charging and no charging. They react much slower than transistor regulators and as a result sometimes do not play well with digital VOMs. Analog meters cannot react quick enough the show the changes in voltage so the resulting reading shows a steady reading. Your digital meter is constantly displaying the voltage it sees when it refreshes the display.

 

Learn something new everyday

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So this alternator doesn't have an internal voltage regulator? I thought all alternators did. Not trying to be a smart ass, just trying to learn so I can get this problem fixed. I don't see an external voltage regulator anywhere on the tractor.

 

 

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You said you changed the alternator, if it had an alternator like a 10SI it would have had an internal regulator. Originally as said above it had a non regulated alternator/generator and a mechanical voltage regulator. What was the one you replaced and what did you replace it with?

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I will have a look for it. These conversations have been very informative. Thanks for your input everyone. 

Mechanical stuff, I can usually figure out but auto electrical is my weakness I'm afraid. Vintage diesel, not much electrical there but gassers are a different story. 

 

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all 656s whether generator or alternator  had external voltage regulators as far as I know then there are farmer conversions to 10 si type alterantors which could have every type of wiring conglomeration you can imagine a picture of the alternator would narrow down the possibilities a lot.

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On 4/21/2020 at 5:14 PM, Owen Aaland said:

Mechanical voltage regulators work by switching between maximum charging and no charging. They react much slower than transistor regulators and as a result sometimes do not play well with digital VOMs. Analog meters cannot react quick enough the show the changes in voltage so the resulting reading shows a steady reading. Your digital meter is constantly displaying the voltage it sees when it refreshes the display.

 

Never once ran into this problem working on old systems with my DVOM. 

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Even a Fluke meter can "jump around" in a "non-steady state" electrical circuit like  PWM valve driver.   I've had cases where I've had to put it in "peak hold" mode.   However....measuring at the batteries themselves there is no way the reading should jump from 2-13.      The fact that it starts fine means there is no problem with the batteries & cables --which leads me to agree, something is screwing up your meter.  No way the voltage can really be doing that.   You need to be looking into the circuitry providing 12V to your ignition.

In fact, the whole problem sounds very much like a "its getting hot" issue.   Does this tractor have an electronic ignition mod on it?   Seen many times where an electroinc module would get hot, fail, cool down & work again.   Or possible the coil is doing the same, although less likely.    The next time the tractor dies, immediately check the points for spark.  If you still have spark there, then its the coil or plugs.  If there is no spark, its switch, wiring, etc.    

I had a small engine once that would die when it got hot - then start after 20 seconds.  Changed everything I could think of...still died.   Finally changed the spark plug....and fixed the problem.    The plug itself was failing when it got hot.   Of course, that was a motor with 1 plug.....unlikely all 4/6 would go bad at once!

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