Do you have your meter set on DC instead of AC?

Your symptom indicate a low/bad battery of possibly a very bad ground.
Get the battery LOAD TESTED. Even new batteries are frequently bad.

When you say you "jump the solenoid switch", exactly which terminal are you jumping?
Jumping 12V to the small terminal should energize the solenoid and crank the engine.

The meter is set on DC. I'm getting 12-13V on the battery side of the solenoid but only 6-8V on the small terminal (on which the wire comes from the ignition switch) when the key is turned to the Start position.

I let the battery trickle charge again and then jumped it from the positive terminal to the small solenoid terminal and it fired up and I was able to mow the lawn. I mowed for about an hour and then tested the voltage on the solenoid after mowing (thinking that running the engine would also help charge the battery), but it still only shows 6-8V on the small solenoid terminal.

The battery was brand new as of yesterday, and it was having the same problem with the old battery. I had the old battery tested and it was pulling 160 out of 275 amps. I did not have the new battery tested, but if the same problem happened with both batteries, could it still be the battery that's the problem?

Are there other ways I can test to see if I have a bad ground other than what I did in #7 above?

According to the schematic, there are no "mysterious" devices between the key switch and the small solenoid terminal.
Just the clutch/brake & attachment switches.

About all I can recommend is to clean the terminals on all 3 plugs.

You could check for voltage at each spot.
OR
Run a voltage drop test on each switch.
Connect + lead "on the battery side of the switch and the - on the opposite side of the switch. Turn key. A good switch should show minimal V drop. A bad switch would show around 6V, since that is about 1/2 of what you SHOULD be getting at the solenoid.

Possibly, just unplugging/plugging the connectors a couple times might clean them up if that's the problem. Else, bad switch.

EDIT- IF the solenoid clicks, it should crank, assuming a good battery & connections.

Also- With the key in the crank position, you might try wiggling the key, C/B Pedal & attachment lever to see if something becomes obvious.

This post was edited by bill_kapaun on Sat, Jun 28, 14 at 12:35

I just thought of something else-

"8. Verified that I have 12V on the B terminal of the ignition switch and also verified that the continuity within the ignition switch seems to work fine when positioning the key between Lights, On, and Start.
9. Sometimes the lights work and sometimes they do not. I took apart the connector and only show around 6V on the light connector terminals. "

IF you used an OHM meter to verify continuity, the switch may still be bad.
I'm starting to think that is the real problem, since you are also having low voltage to the lights!

Thanks for the continued advice. When you mention doing a voltage drop test at each "switch", do you mean at the seat/clutch/blade safety switches?

I ran another test today by measuring the voltage at the solenoid switch. It was still running around 6V, so I removed the ignition switch and then jumpered pins B, A1, and S together. I then had a solid 12.7V at the solenoid switch. So this tells me, too that it's the ignition switch. I'm ordering one from amazon now and will send an update after I have tried it!

Don't rule out corrosion on the connecting plug.

IF you are getting THAT MUCH voltage drop, you should be showing some amount of resistance across the switch.

You might also "modify" your test and just check B&S and B&A1 separately.
A1 "feeds" the carb fuel solenoid, so there should be a bit of a draw on that circuit.
I'm pretty sure the carb solenoid doesn't draw nearly as much current as the starter solenoid, so I'd expect to see a "lesser" voltage drop there.

You might want to unplug the Voltage Regulator from the engine to do your tests just to make sure it hasn't gotten "wonky".

Since you mentioned the headlights are also acting up, I'd somewhat confidently say it's the "B" portion of the switch or plug.

Well I received the new ignition switch today and it didn't help...no change. However, with your comments, I found something else that might be the problem.

I've attached a picture (part and connecting wire circled in yellow), and I believe this is the fuel solenoid?

With the wire connected to the fuel solenoid, when the switch is in the ON position, I get roughly 4V at the fuel solenoid. Also, when the switch is in the Lights position, I get 4V at the lights. And when the switch is in the Start position, I get 4V at the small solenoid terminal.

When I DISCONNECTED the fuel solenoid and run the same tests, I get 12.5V where I previously only got 4V.

Does that mean the fuel solenoid is definitely the problem? Or could it still be something else? I want to be sure it's the problem as the part looks to be over $40.

Thanks, and Happy 4th of July!

Does the engine CRANK with the fuel solenoid disconnected?
(It won't start)

No it does not crank. I get 12.5V on the wire that connects to the starter solenoid but when I connect it, I still only get 4V.

Here are some other items I tested today:

1. I pulled the fuel solenoid and verified that it held the pin in when 12V was applied and let it out when 12V was no longer applied. I also measure 38 ohm across the fuel solenoid when it is not connected. Is this ok?

2. I tested jumpering the ignition switch pins B&A1 and B&S separately as you mentioned. When B&S are jumpered, the voltage between these pins drops to 60mV. When B&A1 are jumpered, the voltage drops to 4V. These were done with both the fuel and starter solenoid switches connected. When they are disconnected, the voltage on B&S does not drop at all and the voltage on B&A1 drops to 11V.

3. I noticed some strange issues with the lights. With the fuel solenoid disconnected, I get 12.5V on the light connector, but as soon as the lights are connected into the circuit, it drops to 400mV and the lights do not come on. Maybe this is a separate issue? I've disconnected the lights for now as I don't think it should matter whether they are connected or not.

38 ohms sounds about right for a fuel solenoid. About 1/3 amp.

It's really sounding like you have a bad ground somewhere!

Do some ground circuit voltage drop tests.
Put the - lead of the voltmeter on the NEGATIVE POST.
Turn key ON with lights ON.
With the + lead of the meter, start working"backwards" placing the + lead on...
Neg bat terminal, cable, frame, engine block etc.
IF you find a HIGH reading, that's your bad connection.

I tested around for a bad ground, and got 0V on everything I tried...until I tried the long bolts coming down from the plastic battery housing to hold the battery in place and found that they both had around 5V on them! I unscrewed them, removed the battery, cleaned everything I could find, and then reconnected everything, and voila--12V everywhere and no voltage on the bolts. I still don't know how why the bolts had voltage on them because they connect at the top and bottom via plastic. There was a bit of corrosion on them, so maybe that's what caused it. Now the mower starts and runs better than it ever has.

Thanks for all the help!

A dirty battery top can conduct electricity to some degree.

One problem with the newer digital meters is they draw such little current, it's easy to get a higher voltage reading than with the older meters that "loaded" the circuit down more. MegOhms vs a couple kOhms.

Methinks you may have simply had a bad connection between the battery terminal & battery post.That's why I specify connecting to the POST and working from there.'
Glad it's working!