I think the 4th post is to bypass the ignition resistor on older cars.
I'm assuming this has 2 large & 2 small posts?
If so, try the other small post.

"I'm assuming this has 2 large & 2 small posts?
If so, try the other small post."

One of those small posts is the ground. Best use a multimeter and find out what posts you are dealing with. I don't see any need to have replaced the original 3 post solenoid. It, the original, MIGHT have needed the mounting surface cleaned to be sure it was grounding.

I don't recall the details of the previous post but are you sure the valves don't need adjusting? Of course you have to get the starter solenoid thing straightened out now.

Walt Conner

You can test to determine if the 2 small posts are "pair" in the same circuit (one being the "hot" and the other being the ground) and you had better test before you arbitrarily try hooking one of them to a ground. To test, you need either an ohm meter or a continuity tester. Using the ohm meter or continuity tester, touch the tester probes to both small posts (DO NOT TEST THE BIG POSTS). If it indicates that continuity exists between the 2 posts, then one of them is a ground (and it doesn't matter which one). If your testing indicates that there is not a connection between the 2 small posts, touch one test probe to a small post and the other probe to the metal case of the solenoid. If that shows continuity, the case provides the ground and the small post is the one to connect your small wire (from the old solenoid). If you get no continuity from that post to the case, leave one probe on the case and touch the other probe to the other small terminal. If this post has continuity to the case, this post is where to connect your old small wire. If you have found continuity between a small post and the case, the additional post will serve no purpose in your application because it was, as bill said, to "bypass the ignition resistor while cranking". If this turns out to be true you can put a dollop of RTV (silicone sealant or caulk) over the post if you want to insulate it and keep on mowing.

To test the 4 post solenoid: Remove the solenoid from the tractor. 1. Hook a jumper wire from the negative post on the battery to the solenoid body. 2. Hook a jumper wire to the positive side of the battery. Touch each of the small terminals until you hear a click. The one that clicks is the one that should be connected. If you hear no click then one small terminal goes to ground and the other to the existing wire.(It doesn't matter which one you ground.)

Thanks guys. Let me again say that I'm kind of mechanically challenged, but trying to gain some knowledge. I have a cheapo multi-tester (Cen-Tech multimeter #90899), but never used it before. Do you think this would do the job to test? ? What setting should I use (the instructions are very vague - dcv,acv,dca,200-2000k). Also not sure how to interpret the reading output results?

By the way, the solenoid body/case is plastic. Don't see how that would test continuity. We hooked the new solenoid up exactly like the old was without anything on the 4th small post. Also, moved the wires from the left small post to the right (4th) small post and nothing.

If I can't understand how to use this multi-tester, I guess I could try to test the solenoid using ray_okla's method. Better than just sitting here.

Here's close pics of the old 3-post and new 4-post plastic-bodied solenoids:
old-
{{gwi:328423}}
and new (universal) -
{{gwi:328424}}

And one more pic of the original solenold before taking it out (the ground is attached under the top left post):
{{gwi:328426}}

"(the ground is attached under the top left post): "

I think you had better get some help on this. The wire attached under the top left post in your picture is most likely the wire from the alternator!! Be careful or you are going to do some serious damage here.

Walt Conner

Thanks for posting pics, and for stating that the case of the replacement solenoid is plastic. As walt 2002 said, one of the small bladed terminals a ground. Since the old solenoid did not have a separate ground wire, you will need to make one. Auto parts stores or hardware store will have the necessary terminals if you don't have them on hand. All you need to do is make a wire about 3 inches long with a female blade terminal on one end and a 1/4" eyelet terminal on the other end. Connect the blade end to one of the blade posts on the new solenoid, put a solenoid mounting screw through the eye terminal and screw this through one of the solenoid base mounting holes when you install the solenoid. When you secure this screw to the lawn mower, it will provide the ground for the solenoid. The old small wire that has the eye terminal (the one that was paired to one of the big post) has to go back to the same cable post it was paired with on the old solenoid. It goes with the positive cable that goes to the battery.

At this time, I'd also check any fuses. If you hooked it up wrong and tried to start the tractor, you may have blown one.
{{gwi:328427}}
The Ohms scale is in the lower left quadrant., with the "Omega" Greek symbol.
NEVER use that scale for checking Volts!
On the Ohms scale, you'll notice if you touch the test leads together, the meter will read zero.
For continuity, use the 200 scale.

When measuring Voltage, turn the dial to the appropriate DCV position. Always start in a range that covers the highest Voltage you expect to encounter. (Actually, newer digital meters are pretty foolproof, but it's still a good idea to use proper technique)

Thanks for all the further input, guys, especially how to set the meter. If I'm neasuring voltage for battery would the DCV position be the setting, and would I look for 13.8 or whatever it is for full charge? What's an acceptable CCA reading?

Walt and mownie - thanks again for your detailed info.

Update on this current situation:
I took the new battery I bought last week to have tested...no good! HA! Go figure!! So, I bought another battery that tested good at the auto store. Hooked it up and nothing happened again. Took the new 4-post solenoid back off and put on the original 3-poster. At least it tried to crank...but nothing. I remembered the guy at the auto store saying to bang on the starter while I'm trying to start it because it sticks sometimes. I did that and low and behold it cranked up ( I had heard this happens sometimes-with cars too). I let it run for a while, then shut it off. Turned it back on and off a few more times and no problems starting up. So, don't no whether I'll eventially have a starter problem, but right now it looks operable.

Once again I want to thank all you folks for guiding me through this little setback and tips on how to use the meter (by the way, the pic of the meter is exactly the one I have).

I'd like to know more about what readings to expect with different situations, but I guess that'll come, maybe.
Maybe bill_kapaun knows a site that I can read up on how to use my meter more proficiently (instructions suck).

IF measuring DC Volts, you use the DC scale. You'll get erroneous readings if trying to read DC on the AC scale or the opposite.
The only AC readings you would ever expect on L&G equipment are in 2 situations.
1. Directly off the 2 leads from the alternator when they aren't hooked to anything BUT the Vmeter.
2. SOME tractor headlights are ran off an AC tap directly from the alternator.
General DC measurements, you hook the black/common lead to ground and use the RED lead to probe for voltage. A simple 12V test light works just as good for this.
Where they are very handy (and seldom used) is for measuring VOLTAGE DROP.
Think of a battery terminal that is making contact with the battery post. It might "look good".
Place the red lead on the battery POST and the black lead on the terminal. The meter basically "jumps" the circuit and will give a reading. Whatever the meter reads, is the V DROP on that part of the circuit.
You can measure the circuit over several connections such as from the battery post to the stud on the starter motor, or isolate the individual connections such as:
Battery post to battery terminal, terminal to bat cable(wire), cable to next terminal, terminal to solenoid stud, solenoid stud to the "other solenoid stud, etc......
Readings must be taken with the circuit energized.
Sometimes, a lot of .1V & .2V drops over individual connections can result in a large Vdrop over the entire circuit.

Appreciate it, bill. Thanks for taking the time. I'm still not sure I understand, but if I fiddle with a bit I might figure it out.

Do not bang or hit the starter, it will break the magnets and starters are expensive.

Fish

But that's the only thing that worked, fish. What should I have done??

Better to tap it with a wooden or plastic screwdriver handle if you hit it with anything. If you tap it lightly while the starter is engaged (but has not spun yet) and the starter "comes to life", you probably have a "sticking starter", and/or a low voltage/voltage drop condition with the machine. If the light tap gets it going and it starts OK after that (without having to tap it again), good for you, you might make it through the whole season. If it has to be tapped every time you try to start it, you need to check every connecting point in the circuit from battery to solenoid to starter for corrosion and/or loose nuts/bolts. Check the ground attaching points from the engine to chassis and chassis to battery (on most L&G tractors the ground runs from engine directly to battery negative post). If you confirm good connections everywhere and it still wants a "love tap" as foreplay to starting, either your battery is too weak to "kick" the starter or your starter is sticking internally (bushings, commutator & brushes or all 3) and will need to be serviced to eliminate the sticking. Don't ever "clobber" a starter with a hammer or similar object, especially if you are angry at it. Your payback, if you do, will be to purchase a new starter.

What do starters for this 2002/3 Murray Select 42" 16.5hp cost? I'm at work and don't have the engine #. I'm guessing it's healthy.

Anyway, I wasn't "banging" it with a hammer...more like tapping while I tried the ignition key/starter. It started running after that. For how long...who knows?

"What do starters for this 2002/3 Murray Select 42" 16.5hp cost"

I have no idea WHICH B&S 16.5 hp a Murray has on it and I don't see where you have posted model numbers and I don't plan to look them up.

IF it is an OHV single cylinder, the starter from almost any B&S vertical shaft single cylinder engine from 10 hp up will fit it. No point in buying a new one.

Fish is right about banging the starter. Just placing the palm of you hand on the flywheel screen and turning the engine backwards a little would likely have accomplished the same thing.

Walt Conner

Well, got the tractor out yesterday for a mowing. Tried to crank it up and nothing....again. "Tapped" on the starter a few times whiule cranking and it came to life. Apparently, after it's been running a bit you can shut it off and start it back up again with no difficulties. Must be when it's been sitting for a few days it locks up.

Oh, didn't get the model # off the engine (that's apparently the only place I'm gonna find it because it's no where else to be found including Murray op guide and no manual for the engine), but it's a 16.5 ELS OHV single cyl. With trying to get it cranked, running out of gas, and hot as hell, it just slipped my mind.

I have a pretty good local hardware/lawn repair store close by me. Think I'll ask how much to repair the starter (if they even do that work.

Walt - you said not to buy a new one. Not sure where you meant I should pick one up. We don't have many lawnmower junkyards around here.

Walt - I contacted a lawnmower shop that does most of the HD and Lowes repair work. The mechanic I talked to was very familiar with my "starter" problem and said I needed to have my "valves adjusted".

Ironic, I thought, since someone on this forum was just telling me that a day or so ago. Just thought you might appreciate that. BTW, I really wasn't expecting you to go digging all over the internet for my engine # like you mentioned in an other post. I wouldn't have expected that from anyone, but thanks for the other help.

"my "starter" problem and said I needed to have my "valves adjusted"."

I have probably posted that at least 500 times and get requests frequently for my instructions.

Walt Conner

Just bringing this back up to go with the other thread,
some of us like closure.

Fish

Yeah, that's fine by me. Consider this thread closed.

Thanks guys.