Scotts S1642 no start, low voltage condition

[mmahoney626]

I have a Scotts S1642 made by John Deere, and I have a no start condition that I'm not sure how to proceed to diagnose and fix, so I'm reaching out to the community for ideas. I've been attempting to diagnose the

problem for some weeks with no success.

The mower has been working fine, with regular maintenance done. I went to use it, and the mower did not start. I am getting the fuel solenoid click, but starter will not engage. My first thought was to check the

battery, but the battery showed good at 12.8 volts. I checked the voltage at the battery cable attached to the starter, and the starter motor was only receiving 5-7 volts. Over the next couple weeks, and what is now a

series of misdiagnosis and my own self-education on lawn mower electrical system, I am still at a no-start condition.

I did a complete deck rebuild in October of 2014, and the motor and transmission run great. I rebuilt the entire deck, replacing everything except the deck itself, and while the deck was off, went so far as to replace the

transmission drive belt, tension spring, and all the under frame idler pulleys. Rebuilt the carb when I replaced a faulty fuel solenoid. I wanted to make sure that this was the one and only time I was going to have to

perform a job this involved with this mower. When I don't run into situations like this, the mower runs great for being a 2001 model. I don't feel I'm ready to give up on this mower for what may turn out to be a simple

fix.

Before I just started replacing parts I had done the following, with no success, which lead me to start ordering what parts I thought may be faulty:

tried jumping the solenoid, no start, replaced solenoid
tried jumping the starter, no start, replaced the starter
replaced ignition coil, because I didn't know where else to check at this time and was getting frustrated, and thought that by throwing another $70 at it, it would somehow magically start right up
replaced ignition switch, thought maybe not letting complete 12 volts thru, still no start
had battery load tested, passed, still no start
thought maybe one or more safety switches not letting 12 volts thru to solenoid
checked continuity on all switches, passed
something is still not letting 12 volts pass thru something else to get where it needs to be

Battery check from post to post shows 12.8 volts.
Battery check with positive post and ground to frame shows 12.8 volts.
Battery check with positive on positive post and negative to frame, try to start, voltmeter shows drop to 5-7 volts.

All cable/wiring connections are tight and clean.

I've replaced the following with new parts:
starter mower
starter solenoid
ignition switch
positive battery cable
ignition coil

I've tested the following:
battery under load, passed
(battery is less than one year old and I top off the charge with 2amp slow frequently)

continuity checks done and passed on:
PTO switch (under deck left side)
brake safety switch (under deck right side)
seat safety switch

I've gone over the wiring harness to check for breaks or loose grounds, and found none. All wiring harness connectors have been checked and cleaned, ground points are tight.

So I've done all this, and I still have the same problem. The mower won't start, and it seems everywhere downstream of the battery where I should be getting a reading of 12v, when I try to start, I read 5 to 7 volts.

I've been trying to Google this issue for a couple weeks, and everything I seem to find seems to diagnose a problem where 12 volts that gets to a point, then no voltage after. I can't seem to find anything that references

a "not enough voltage" condition like I describe.

I need ideas on what else I can look for that is causing this condition.

 

[logan01]

I assume you are pushing close to 13 volts to the solenoid yet from the solenoid to the starter is single digits voltage? Everything replaced but the battery yet it passes load test. I would first run a good temporary ground wire from the battery NEG post to a spot on the starter / starter mounting bolts. Regarding continuity testing of switches, some folks are less thorough than others. Here's an excellent short video on switch testing. https://www.youtube.com/watch?v=Xi3p465MN1E

When you say you jumped the starter then replaced the starter, did you jump directly from your battery or external source? Same, same with new starter? I don't see a safety switch being an issue causing low voltage unless one is shorting or is causing too much resistance in the starting circuit thus robbing the starter of its required full voltage.

 

[ILENGINE]

Lets get the volt meter out and run some simple test:

Clamp the negative lead of the meter the negative post of the battery, it will stay there for all the following test.

What is the battery voltage?
Now with the positive lead still connected to the positive post of the battery, turn the key to start, what is the voltage?
Move the red lead of tester to the battery side of the starter solenoid, and still in the start position what is the voltage?
Now move the red lead to the other large post on the solenoid going to the starter, and still trying to start the engine what is the voltage?
Move the red lead to the terminal on the starter and while attempting to start what is the voltage?
Now move the red lead to the metal housing of the starter and try to start, what is the voltage?

this will tell us where the problem is.

 

[mmahoney626]

That is a true statement, that I am pushing almost 13 volts to the solenoid, and single digits afterwards, so I immediately thought the solenoid and changed it. That is the same video I saw and followed that process to check my switch continuity. I jumped the (old) starter with battery cables right from the battery to the starter post, it didn't turn, so I said it must be a bad starter. Replaced starter, still have same no start/low voltage condition. I have not tried jumping directly to the new starter, since I had done all of the other things and I'm right where I started.

I can try running a set up jumper cables from the negative post on the battery to one of the attachment bolts on the starter, since the starter grounds thru the body to the frame, and report what happens back to the forum.

 

[mmahoney626]

ILENGINE and logan01, I will print this out, and I won't be able to run all of these tests until I get home from work later and report all of my results.

I ran the above tests, and here are the results:

Test: I would first run a good temporary ground wire from the battery NEG post to a spot on the starter / starter mounting bolts.
Result: Starter did not activate.

Test: What is the battery voltage? Result: 12.68
Test: Now with the positive lead still connected to the positive post of the battery, turn the key to start, what is the voltage? Result: 8.76
Test: Move the red lead of tester to the battery side of the starter solenoid, and still in the start position what is the voltage? Result: 8.47
Test: Now move the red lead to the other large post on the solenoid going to the starter, and still trying to start the engine what is the voltage? Result: 8.25
Test: Move the red lead to the terminal on the starter and while attempting to start what is the voltage? Result: 7.16
Test: Now move the red lead to the metal housing of the starter and try to start, what is the voltage? Result: 0.516

I hope I understood the last instruction correctly, I included a picture to show how I did this.

 

[mmahoney626]

Guys, I've found the issue, and I'm going to post what I found even though I created my own problem due to my lack of knowledge about repairing my lawn mower because it has never had issues that needed repair before. In retrospect, I should have listed the parts I replaced in the order I replaced them. The first part I replaced was the ignition coil to possibly diagnose another issue I was having. I was not paying attention, and did not gap the new coil properly. So the first time I cranked the engine, the flywheel came around, and the magnet came into contact with the side of the coil, so basically I locked it from rotating. I put the old coil back on, and made sure the flywheel could rotate this time, and it started right up. An expensive lesson, but I learned something from the whole process.

 

[logan01]

Not a problem. You learned, you solved. Great job and glad you shared it with us.