Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ride On Lawn Mower

  1. May 9, 2003 #1
    Hello. My ride-on Lawn Mower broke down recently. And i'm not a real mechanics or automobile person so please help me out. (it requires a bit of knowledge on circuits)

    When I turn on the ignition, usually the engine rev's a bit. And then I try it a couple times until it works. Takes about 2~3 shots. But last time. When I was mowing half-way through my lawn, I found a piece of rock on the grass so i turned off the engine to get off and to kick that rock out of the way. But when I got on, I couldn't start it. It just clicks and nothing happens. I opened it up and it wasn't the engine clicking. It was the solenoid connected to the ignition. The solenoid was screwed on tightly to the side of the inside of a compartment just below the fuel tank. (close to the ignition) So i unscrewed it and realized that every time it clicks, it's electric current running from the side of a solenoid metallic piece to the side of inside wall of that compartment. (which is also metallic) That's what's making the noise. I, having no idea what that meant, am asking you (who can help out):

    Is that solenoid broken? or is it something else that's broken?

    I read thru the manual (which didn't help me any cuz I only looked at the pictures and couldn't understand any of the technical words) and it basically said that when this happens, there are these possibilities:

    1.) Battery not enough juice in it

    2.) Solenoid needs to be replaced

    3.) Starter (Ignition Keyhole) needs to be replaced

    4.) Incorrect Wiring


    I charged that hunk of battery already and found out it wasn't the battery problem. I looked thru the starter and it seems okay to me. And i didn't even touch the wiring so i didn't think it was the wiring problem. So is that solenoid broken? Please help. Thank you.
     
  2. jcsd
  3. May 9, 2003 #2
    So it's not the battery, hmmm.

    The solenoid makes use of electomagnetics and causes what often looks like a large 'washer looking thing' atached to a plunger (all inside of the solenoid) to slam up against two metal contacts (basically the enlarged head of a bolt). These bolts stick out from the solenoid and have the positive battery cable connected to one of them, while another large cable runs from the other one down to your starter. When you energize the solenoid (to crank the engine) you will hear the 'washer thing' make contact with the bolt heads.
    Ok, if you're still with me, what can happen is the contact surfaces inside the solenoid get pitted and burned. In this situation it is possible to hear the solenoid make contact but still the engine won't crank over.
    Here is a quick way to isolate the problem to either the solenoid or starter motor; make a connection directly to the starter motor from the battery. You can do this in a number of ways, so figure it out for yourself if you can. Anyway, if the starter now turns the engine then it is likely time to think about repairing or replacing the solenoid.

    Good luck

    [edit]
    BeefyBeef, I see this is your fist post and that you are the newest member. I'm sure we've spoken in PF2 though, but just in case I'd like to say a big 'HELLO':smile:
     
    Last edited by a moderator: May 9, 2003
  4. May 9, 2003 #3
    If you have enough mechanical knowledge to know what you are doing, use a "car battery jumper cable" (One side only) to connect the positive side of the battery, directly to the starter motor, to tell you if the starter motor is still working properly.

    Most starters are 'negatively grounded', you can tell simply by looking to see if the battery is negatively grounded, negative wire connects to the frame, or motor, metal, which works only with a negative ground starter.

    This means that the wire connecting the solenoid to the starter, the big heavy one (wire) is the positive wire and the starter should turn over when you touch that with a positive cable end.

    (WATCH OUT FOR THE SPARKS, KEEP THEM AWAY FROM THE BATTERY, BATTERIES ARE EXPLOSIVE WHEN GASSING! VERY DANGEROUS!!!)

    If the starter turns over when HOT, the starter is probably still good, and the solenoid is suffering heat damage and needs replacing, otherwise the starter might just be 'ceasing up' due to heat/age/overuse/time/bushing damage, or just plain, it broke!


    EDIT SP!
     
  5. May 9, 2003 #4

    GENIERE

    User Avatar
    Science Advisor

    I am almost as good at starting small engines as I am at stopping toilet tank leaks.

    In order of probability:

    - Discharged battery (magneto may be bad or battery may be bad)
    - Corroded or loose battery terminal connections
    - Corroded or loose ground connection from negative terminal to chassis
    - Corroded or loose solenoid or starter connections
    - Less likely but possible. At least one bolt mounting the solenoid, starter, and engine (three bolts total) must be tight and free of corrosion to provide ground point.
    - Bad solenoid or starter

    Regards
     
  6. May 12, 2003 #5
    This statement is a little confusing, inasmuch as when engaging a starter the engine does NOT usually "rev".

    From reading into what you've written, I suspect that what you are telling us is that when you turn the key, the starter revs without turning over the motor, is that right?

    Because if that is the case then it could simply be a combination of broken or breaking parts, both the solenoid and the starter, particularily the bendix on the starter.

    The Bendix is the device that causes the gearwheel of the starter to engage the flywheel, hence if you turn the key and the bendix is not functioning properly, then starter motor will spin at full pace, without turning over the motor itself.

    Repetition of the 'key turning' (Starting) might cause the bendix to begin working as they are usually mechanical in nature, sometimes stick, and would then cause the motor/engine to begin turning over.

    A better explaination of the problem might help, if you haven't already found the answer. A bendix is 'repairable'.

    Note, if the solenoid is mounted away from the starter, then the bendix is in the starter, and operates by means of the starter. If the solenoid is mounted on the starter, then the bendix can/could be the type that is operated off of the solenoid itself.

    A misfunctioning bendix will allow the starter motor to turn without turning the motor. This could be combined with a solenoid that is, has become, heat sensitive (Won't work when hot) or a starter that is heat damaged (Won't work when hot) or a bendix that is jamming, or several other possibilities.....needs better explaining..thanks!
     
  7. May 13, 2003 #6

    megashawn

    User Avatar
    Science Advisor

    Uhm, are you sure this will work? It seems that if you only take the positive side of the battery and connect it to the starter, without grounding that starter to the same battery, then it will be an open circuit and no current will flow.

    Everything else sounds like a good plan though.
     
  8. May 15, 2003 #7
    No where have I suggested that you remove the starter from the vehicule, ergo it is still grounded, because it is bolted to the engine. (at least it should be!)

    This is simply a 'hotwired' method of speed testing the starter motor.
     
  9. May 15, 2003 #8
    Ah, Mr Parsons has a valid point that has shown me an error in my thinking. I had intially confused myself thinking that the jumper cable was comming from another vehicle. In that case you would have to complete the loop with a ground. Perhaps Megashawn made the same mistake as well.

    [edit]
    I hope that BeefyBeef will not remain a 1-post wonder, but come back and let us know how it all turned out.
     
  10. May 15, 2003 #9

    megashawn

    User Avatar
    Science Advisor

    yes, I to made the same assumption.

    I think it was:
    and I merely thought of using a second vehicle.

    Thanks for clearing that up.
     
  11. May 16, 2003 #10
    DITTO!

    (Hadn't I mentioned that it was merely to "bypass the solenoid", the car jumper cable, sorry that it mislead you, I will try to remember to be specific enough to avoid things like that, years of experiance in the Auto industry(ies) even managed a Large Auotshop and had to explain to customers what was wrong with their cars......OYE!!)
     
  12. May 16, 2003 #11

    megashawn

    User Avatar
    Science Advisor

    I know what your saying. Kinda like explaining how a computer works, or what is wrong with one to a person who merely uses the computer.
     
  13. May 17, 2003 #12
    Knows that one, one of the places I go to use computers the people 'in charge' of the computers, know way less then I do about them, (Most, not all) so they seem to always want to tell me not to play with them, removing the personalizations that people make to public computers, taking out spyware, shutting down the innumerable program downloads that they have all, "starting up" uselessly, that diminishes the RAM ability of the computers to the point that you click on a file dialogue box, and the hourglass comes up for thirty to sixty seconds, OYE!

    Can't explain to them, how to help themselves.
     
  14. Jun 16, 2003 #13
    word... I went to kinkos to scan something, and the peice of crap machine has the hourglass pop up for 2 minutes at a time. So i was getting charged while not being able to do anything. Well I gave them a peice of my mind on that one!

    That also reminds me of a time some sales rep pissed my dad off so bad, he went back later and fdisked a computer. Pretty cool since it only takes 10-15 seconds to delete the primary partition, but most places protect themselves from such occurences these days.

    To the original problem,ounds like the solenoid. I just had the same problem on my car. The starter works fine with no load on it, but upon further inspection, I saw that the copper washer that connected the current to the started had almost completly arced out. So I ended up getting a new started for 120 bucks for 50 cents of copper that needed replacing, I was very tempted to fix it myself. Oh ya, and do make sure the battery terminal and other connections are clean, and that the battery is good.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?