Starter will not crank. Need electrical help. Now fixed but learn from me.

[supergen]

The advice I've seen in this forum is very impressive. So I'm sharing my story - and it is humbling. The moral of this story is to not skip the simple things. CHECK THEM FIRST.

I was about to send this (See "The original story..." below) but after I typed this I figured I'd do a bit more troubleshooting. I tore apart more of the tractor so I could get to the battery ground on the engine block. It was corroded. Not easily seen due to the typical grass/grease/muck in there but once I took it apart the joint, the bolt, nut and ends of the two grounds that go there were corroded. Cleaned it up with a file, wire brushes and a dremel and WHA LA!!! Tractor cranks like normal! The ground was the problem. I'm sharing this because $75 in parts and 20-25 hours of labor/research/fretting later, it was a ground issue. And aruguably the first oneI should have checked. If I had taken things apart to get to this first, it would have save me a lot of time and money. But I didn't because the problem seemed to be a starter issue since the starter wouldn't turn over when the solenoid was jumped. Then I figured it must be the solenoid since the starter didn't fix it. Then I get more into it with the meter and saw the strange voltages (after $75 in parts). Then I said - come on - it won't crank at all now! And back to basics - tear more things apart and start from the beginning.

Turns out - the ground was so bad that the battery couldn't deliver the proper voltage and current to the starter. Couldn't even get the solenoid to fully engage! I had to keep the battery fully charged recently - I guess to overcome the bad ground...

I'm not an electrical engineer and can't explain why the funny readings were received below - maybe someone else can for my learning - but it had me off starting to look at safety switches, wiring, etc... I was even wondering why my batter was dying so often. It was likely the small voltage draw when the key was left in the on position.

If you can explain the strange voltage readings below - I would be appreciative. To all others - hopefully you aren't as lazy about checking grounds as me.
_________
The original story/request for help (Now no longer needed):

I own a Craftsman Zero turn ZTS7500 (107.26786) mower and owners manual but no electrical diagram. Tractor has had an issue where it would not always crank when the key was turned. Seemed like the starter. I replaced the starter and no improvement. Next the solenoid was replaced. Mower would crank occasionally, but not every time the key was turned. And now since I started doing more electrical troubleshooting, it won't crank at all when the key is in the 'START' position. With the new 4 pole solenoid I took some more readings.

Four terminals: #1 solenoid left side from battery + terminal; #2 solenoid right side to starter; #3 small left side (Blue wire) (under terminal 1); #4 small right side (yellow wire) (under terminal 4).

Battery was bought in July and was load checked and shown to be good earlier this week. I left the key "ON" all night and it drained from 12.7V to 12.3V when I took the readings below. (See voltages below when key is in 'ON' position). It's on a Battery Tender right now. So, here is what I've been able to find:

With the key in the OFF position I have the following voltages:
#1: 12.3 Volts; #2, #3, #4: 0 volts

With the Key in the ON position I have the following voltages:
#1: 12.3 volts; #2: 0.6 Volts; #3: 0.6 Volts; #4: 0.6 Volts

With the Key in the START position I have the following voltages:
#1: 12.3 volts; #2: 2.5 Volts; #3: 12.1 Volts; #4: 6.4 Volts

With the Key in the START position I have the following voltages:
#1: 12.3 volts; #2: 2.5 Volts; #3: 12.1 Volts; #4: 6.4 Volts

If any of the safeties are not engaged, or the PTO switch is on, the voltages are all 0 on #2, #3 and #4 terminals.

Now I get nothing when I turn the key. I've also tried shorting across the solenoid and get a few sparks but no crank.

I'm having trouble figuring out where to look from here. And I don't have electrical diagrams - if someone can provide them it would be a huge help. I suspect something with the key switch, or ground, but don't know how to troubleshoot the key switch.

Thank you!

 

[bertsmobile1]

One would have hoped you came across on of the std replies I give for non cranking.
It will be tacked onto the end of the reply so it can be overlooked.
If so you will note that mostly it is a works / doesn't work type of test.
I am a big fan of bypassing rather than measuring for this exact reason.
People get hung up on the actual numbers some of them even post them to 2 decimal places, as if .0x V makes the slightest difference.

Meters with numbers are for electrical technicians who understand what numbers actually mean.
If yo press the probes on most meters harder into the surfaces , you will see the numbers change, particularly when measuring resistance.

Now as to your funny readings.
The solenoid is nothing but a relay or electrically operated switch if you like.
They come it 2 varieties, 3 pole & 4 pole.
The 3 pole uses the body as the 4th terminal.

SO there are 2 trigger terminals , the small ones down the bottom.
One has to be 10V or better and the other has to be ground
In your case that looks like # 3 & # 4
To make things confusing , the ground circuit ( # 4 ) is also switched on a lot of ZTR's

If all is working properly in the start position you should see
#1 battery voltage
#2 battery voltage ( - voltage drop according the OHM's law )
#3 battery voltage
#4 ground .

Now because of the resistance in terminals, you can get different numbers depending upon where you put the ground probe.
Another reason for not using numbers.

Power is measured in Watts and the starter motor does not care how it get the Watts just so long as it gets all of them.
So to put numbers in ( not real ones )
A 1200W will draw 10A if it is getting 12V 12 x 10 =1200.
If the ground is bad and it can only get 6V that will double to 20A
If the voltage drops to 2 V then it draws 60A

Amps passing through a wire generate heat, heat increases resistance , increases resistance drops the voltage , dropping voltage raises the Amps and you see we are now in a self feeding closed loop which ends up in something going bang or bursting into flames.

Now the solenoid has a spring ( heat sensitive & is a plastic moulding ) so running too many amps through it can cause damage.

If the ground trigger wire is controlled by relays then you can get some back voltage

SO for now, pull both of the trigger wires off the solenoid and use some thin jumpers to jump direct from the battery to them
Or jump from #1 to # 3 and #4 to ground.
If he solenoid does not fire then running it with the bad ground has fried it.
However if you still have the old one it will most likely work fine.

Remember you also need a good ground at the starter motor and check the power wire to the starter motor for corrosion or burning.

Standard no crank reply

I like to start from the starter motor and go backwards .
Do the following 5 tests, regardless of the results from an or all of them as there can be more than one problem and you want to isolate where the problem lies.
Elimination of individual parts is important so you know by the end, the battery, solenoid & heavy power circuits are all in good order.

1) try to jump the starter motor directly from your car or truck.
+ on the starter first then - to a good ground near the starter ( drain plug of lift hook are good )
Starter turns = starter good

2) do the same directly from the mowers battery
Starter turns = mower battery good
No turn = duff battery, recharge it & try again.

3) check for voltage ( + 12V ) at the solenoid trigger wire with the key in start position
3a) same with ground trigger wire ( 4 wire solenoid ) or body of solenoid ( 3 wire solenoid)
( I like to test V from the battery hot terminal to ground terminal rather than ohms as they give funny readings )

4) leave ground jumper in place ( from step 2 ) & try key start.
Starter turns = power connection good but ground connection suspect ( most common )
Confirm it by trying again, extra ground removed

5) Remove the trigger ( thin ) wire / wires from the solenoid.
Ground one on a 4 wire solenoid & bridge from the hot terminal to the other.
Starter cranks = solenoid good.
Solenoid is not polarity sensitive, BUT THE WIRING IS so make sure you remove the thin control wires.
Note a thinner wire on the hot terminal is not a control wire. It is the main power feed to the mower.


From here on things become very mower dependant as starting circuits are getting changed all the time.
Basically the power goes in a loop from the hot side of the solenoid ( saves wire, no other reason ) through the fuse to the B terminal on the key switch then to the PTO switch then to the parking brake switch then to the solenoid trigger switch , easy peasy after you grow the 3rd arm. Use a test lamp and follow the power.
However a lot of mowers with a 4 pole solenoid, run a secondary ground control circuit to the ground solenoid wire through the lap bars.
Then to stop this interfearing with the normal safety function of the ground kill, it goes to a relay with the ground as the switched connection.
These are a PIA as the + control wire to the relay comes from the power loop above and the ground side of the control comes via the normal cut out functions of the lap bars.
Be very careful because if you have a system like this and accidentally send 12V down the ground loop you can fry the magnetos on some circuits.nd from the grounding bolt to one of the starter mounting bolts & paint over both with liquid electrical tape.

 

[supergen]

Bertsmobile - thanks for the detailed reply. Your standard no start instructions would have saved me $60 for a new (used) starter. I have learned a lot about grounds and troubleshooting this system and your explanation helps even more.