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Small Engines (Lawn Mowers, etc.)/Charging Issue With John Deere LX255

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QUESTION: Sorry for the detail here, but I figured the more information  I provide, the easier it is to diagnose.

I have a John Deere LX255 lawnmower with a 15 hp Kohler engine. The battery was dead Saturday, with no indication that it was charging at all after 36 hours of connection to a Battery Tender. Monday, in a hurry to get to some quick cleanup work done, I jumped it from my (cranked and running) Jeep Liberty. Big mistake, but good lesson learned. As I'm sure you have guessed, I burned one of the resistors on the ignition module, so I purchased a new ignition module and a brand new 300 CCA battery from John Deere late Monday afternoon and got both installed. That’s the background. Now here is/are the problem(s).

(1) The new battery late Monday afternoon would turn but not crank the engine. (The “not cranking” is a compression issue I’m  aware of in the 16-year-old engine, but it WILL crank when you are patient and coax it long enough – so even though I'm definitely not a mechanic, I'm "pretty sure" that is NOT the issue I’m dealing with here. I'm convinced I have an electrical problem.)  

(2) The battery (Monday afternoon, right after installation) seemed to be weak and to start to drain very quickly, so I tried jumping from the Jeep again (this time it was NOT running), and this time – with patience and coaxing – the mower cranked right up (after one loud backfire), as it had been doing for several weeks. I then immediately disconnected the jumper cables. The red light and green light on the ignition module both were lit, the engine was running smoothly, and everything seemed fine, except that the yellow battery light on the dash was on, indicating the mower battery was not charging. (I did NOT try to engage the PTO, since I wasn’t sure at that time if the red and green lights were “good” signs or “warning” signs.) Lots of research on the Internet last night indicated that the red and green lights being on were indicators of proper operation -- so please let me know if I misinterpreted the information I found.

(2) I didn’t check the voltage on the battery Monday afternoon, either while it was running or not running, but Tuesday morning I checked when it again failed to do anything but turn the engine over without cranking it. It showed 12.3 volts or so. I did not checked the voltage when the engine was running because it didn’t crank right away, and then didn't cooperate when I tried to jump it from the Jeep, although it was spinning and trying hard. I did check the voltage after I killed the engine. It was down to 12.0 volts. I then tried alternately several times to crank from the mower battery, and with jumper cables from the (not running) Jeep. The Jeep battery was turning everything fine, but the mower battery makes only a dull effort during 15 seconds to half a minute of repeatedly turning the key engine before I get the “click-click-click” of “not enough juice” when I turn the key.

So I guess my first question is, what would cause the brand-new lawnmower battery to drain so quickly? As I said, I bought it Monday from the John Deere dealership. The 300 CCA was what they recommended. I’m  hoping either a loose connection or a bad voltage regulator turns out to be the reason why the yellow “not charging” light stayed on when the engine was running – but I’m  puzzled about what would cause the battery to go from brand new, spinning the starter on Monday afternoon, spinning the starter for a couple of minutes this morning, then starting to die, providing just enough juice to get the “click-click-click” when I try to crank it.

Where do I start, and what all do I check to find the source of the drain? Or is it possible that something other than a drain is the culprit? I don’t think it’s a bad  battery, jut based on the initial power on Monday afternoon -- although I am a little suspicious that it was quickly evident that it provided the kind of power I was getting from my Jeep battery for only a minute or so before I realized it sounded as if it were getting weaker.

Would appreciate any feedback you can give me.

ANSWER: The first thing I would do would read up on testing for voltage drop across battery cables.

I have had some old cables corrode, on the inside of the insulation, and cause current flow issues.  Current is the power producer...not voltage.  Voltage is often a good indicator.

If you have a volt meter, you can dis-connect the negative battery cable and connect the meter in series to see if there is any voltage reading indicating a drain.  You can do a quick check with a 12 volt test light but you will not know how much drain there is.

Another test is to measure the voltage with the engine off.  Start the engine and run to full speed.  Measure the voltage with the engine running full speed and compare the readings...you should see an increase.

You could also connect the meter lead to the battery terminals and monitor the voltage.  I have a volt meter connected to my Honda motorcycle which are known to have regulator problems...I just monitor the voltage.

Let me know if there is an increase in voltage with the engine running at full speed.

Eric

---------- FOLLOW-UP ----------

QUESTION: Eric, Really appreciate your quick feedback. I thought I replied to you yesterday, but must have done something wrong because I'm not seeing the message.

Anyway, I used all day Tuesday to fully charge the new battery, then checked the voltage with all cables connected on Wednesday morning to verify I was getting good voltage at every point (battery posts, cable connections to battery, and cable connections to starter and ground). Everything checked out at a little over 12.8 volts. So I let the mower sit all day Wednesday, without connecting anything or trying to crank it, so I could check the battery again this morning to see what the voltage showed. It was between 12.7 and 12.8 volts on the multimeter.

Then I disconnected the positive cable and inserted the multimeter in series to see if that would show a drain, which with the meter set on 200 ma, it showed a .57 ma current flow.

Then I finally coaxed it to crank (after another loud backfire), and I checked the voltage with the engine running at full speed. I was getting 13.8 volts across the battery posts, and although the battery light qwas still lit on the dash, it appeared to be charging OK. (And I never noticed the battery weakening at all as I tried to crank it -- which leads me to believe the battery was nowhere near full charge when I brought it home from John Deere, and the dragging battery was fixed by the Battery Tender topping it off).

Next step -- I engaged the blades and started to mow, listening for unusual noises and alert to any odor that might indicate an electrical problem. Everything was fine, for about five minutes of mowing.

Suddenly, without warning, running at full speed, with no unusual engine noise or apparent loss of power, the engine just stop -- as if I had got off the seat or something. Just powered down completely, and refused to start. The battery was cranking it like crazy, but I was getting nothing internal from the engine.

So now I have new questions.

(1) Do I first check for other electrical problems that could have caused the engine to stop, and now won't let it start again, since the battery light was still on despite the fact that it appeared by the multimeter to be charging? Both lights on the ignition control module were lit when the mower was running, and nothing appears burned on that board.

(2) Or do I next suspect the engine, due to the loud backfires on two of the last three times it cranked? I know the dealership told me last fall the mower (engine) was on its last legs and that the hard cranking was due to a lack of compression. Problem with that is, when it finally cranked during several times at the end of last summer and during the winter when I used it for things other than mowing, it ran fine. No knocking, clicking, or other indication of real motor problems. It has burned some oil for 4-5 years, but I have kept oil in it and even gone to a heavier 10W-40 weight oil to help with the compression.

I have another mower (much more recent vintage), but I want to salvage this one as well. Just don't know which avenue to pursue first, electrical or motor, and would appreciate your thoughts and suggestions.

Answer
The backfiring could be engine related, valves or camshaft timing. Are you familiar with checking valve clearances?

The hard cranking due to lack of compression is false...the less compression the easier the engine is to crank, spin, turnover, or rotate...there is less resistance.

As for electrical, JD uses overly complicated, for a lawnmower, circuit boards and relays with too many lights and gizmos.

Do you have a circuit board under the dash of your JD?

Eric  

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Eric A. Jones

Expertise

Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.

Experience

Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

Education/Credentials
MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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