Mountfield R28M ride on Mower not starting (Again!!)

WIAWSNB

SS, have you tried jump-starting the mower yet? 

By far the easiest first step, and could point to the cause.

Section62

WIAWSNB said:

SS, have you tried jump-starting the mower yet? 

By far the easiest first step, and could point to the cause.

Although every time that key is turned there is potential for more (potentially expensive) damage to be done.  Attempting to jump start with a fully charged larger capacity battery might work.... or it could just do (potentially expensive) damage more efficiently.

There are some steps - such as checking the engine turns over freely by hand (done safely) - that would be wise to do before attempting a power crank again.

WIAWSNB

Just one single, one-second turn required.

Section62

WIAWSNB said:

Just one single, one-second turn required.

And in that one second sujsuj could bend the con rod, bend a valve stem, or punch a nice valve-shaped hole in the crown of the piston.

For those who've been following the lawnmower saga, this is the same mower that had hydraulic lock on a previous occasion when it wouldn't start.

One of the forum's most knowledgeable members said at the time "...If so, it's fortunate that the starter motor isn't powerful enough to 'force' it around, which could cause major damage."  I agreed with that poster then, and I've quoted them here as I agree with them now.

So trying to jump start an engine when you've not done the basics like checking whether it turns freely risks doing exactly what that poster said could happen - sujsuj may have been lucky so far that the old and ancient battery might not be able to deliver the cranking current that leads to major damage.  Connecting a new or higher capacity battery and flicking the key could easily deliver the torque that does fatal damage to the engine.  Or for a less bad outcome, removes the remainder of the teeth on the starter pinion.

It isn't that trying a jump start is a bad idea.... just that doing a jump start without first doing some basic checks isn't a very sensible course of action.

So sujsuj should do some routine checks.  For example disconnecting the spark plug and checking - BY HAND - whether the flywheel turns freely.  Because doing that may save him the cost of a new engine, or a new mower.  The engine being seized after a winter of non-use isn't beyond possible, and certainly more of a possibility than most people will have of encountering small-engine hydraulic lock in their lifetime.

WIAWSNB

Section62 said:

WIAWSNB said:

Just one single, one-second turn required.

And in that one second sujsuj could bend the con rod, bend a valve stem, or punch a nice valve-shaped hole in the crown of the piston.

For those who've been following the lawnmower saga, this is the same mower that had hydraulic lock on a previous occasion when it wouldn't start.

One of the forum's most knowledgeable members said at the time "...If so, it's fortunate that the starter motor isn't powerful enough to 'force' it around, which could cause major damage."  I agreed with that poster then, and I've quoted them here as I agree with them now.

So trying to jump start an engine when you've not done the basics like checking whether it turns freely risks doing exactly what that poster said could happen - sujsuj may have been lucky so far that the old and ancient battery might not be able to deliver the cranking current that leads to major damage.  Connecting a new or higher capacity battery and flicking the key could easily deliver the torque that does fatal damage to the engine.  Or for a less bad outcome, removes the remainder of the teeth on the starter pinion.

It isn't that trying a jump start is a bad idea.... just that doing a jump start without first doing some basic checks isn't a very sensible course of action.

So sujsuj should do some routine checks.  For example disconnecting the spark plug and checking - BY HAND - whether the flywheel turns freely.  Because doing that may save him the cost of a new engine, or a new mower.  The engine being seized after a winter of non-use isn't beyond possible, and certainly more of a possibility than most people will have of encountering small-engine hydraulic lock in their lifetime.

All very sensible. I did say in my very first post, "First check that the engine isn't seized."

Section62

WIAWSNB said:

Section62 said:

WIAWSNB said:

Just one single, one-second turn required.

And in that one second sujsuj could bend the con rod, bend a valve stem, or punch a nice valve-shaped hole in the crown of the piston.

For those who've been following the lawnmower saga, this is the same mower that had hydraulic lock on a previous occasion when it wouldn't start.

One of the forum's most knowledgeable members said at the time "...If so, it's fortunate that the starter motor isn't powerful enough to 'force' it around, which could cause major damage."  I agreed with that poster then, and I've quoted them here as I agree with them now.

So trying to jump start an engine when you've not done the basics like checking whether it turns freely risks doing exactly what that poster said could happen - sujsuj may have been lucky so far that the old and ancient battery might not be able to deliver the cranking current that leads to major damage.  Connecting a new or higher capacity battery and flicking the key could easily deliver the torque that does fatal damage to the engine.  Or for a less bad outcome, removes the remainder of the teeth on the starter pinion.

It isn't that trying a jump start is a bad idea.... just that doing a jump start without first doing some basic checks isn't a very sensible course of action.

So sujsuj should do some routine checks.  For example disconnecting the spark plug and checking - BY HAND - whether the flywheel turns freely.  Because doing that may save him the cost of a new engine, or a new mower.  The engine being seized after a winter of non-use isn't beyond possible, and certainly more of a possibility than most people will have of encountering small-engine hydraulic lock in their lifetime.

All very sensible. I did say in my very first post, "First check that the engine isn't seized."

Sure, but bearing in mind previous threads it was a bit risky to go on to say jump starting is "By far the easiest first step"... without getting sujsuj to confirm he'd already done the other 'first step'.

I'm sure all of us want the same thing... for sujsuj's mower to be rescued again, and for them both to have a very happy season of mowing.  He just needs to be careful to do all the first steps in the right order.

sujsuj

Thanks for all your input — much appreciated.

I was trying to ensure the battery is fully charged. Until now, I had been charging it while it was still connected to the mower. This time, I completely removed the battery and am charging it externally using two chargers — my car battery charger and the original charger that came with the mower.

The yellow charger is a 12V pulse repair charger. It now shows "FUL" (fully charged). The other charger is lower-powered and hasn't yet reached "FUL", but I'm continuing with it to achieve a full charge.

After seeing "FUL" on the yellow charger, I tried to measure the voltage and current of the battery. However, when attempting to measure the current, the multimeter lead got extremely hot and the wire almost melted. I’m not sure what I did wrong while trying to measure the current.

I did check online, and one concern I have is whether my multimeter's maximum amp rating was too low — could that be the reason this happened? Are there any other possible causes?

In the meantime, I’ll continue charging the battery with the original charger until it also shows "FUL". Once that’s done, I’ll try the other checks and suggestions mentioned earlier.

As I mentioned about 4 weeks ago, I was able to use the mower successfully after a full charge — which is why I’m puzzled about what’s gone wrong now.

Section62

sujsuj said:

...

After seeing "FUL" on the yellow charger, I tried to measure the voltage and current of the battery. However, when attempting to measure the current, the multimeter lead got extremely hot and the wire almost melted. I’m not sure what I did wrong while trying to measure the current.

I did check online, and one concern I have is whether my multimeter's maximum amp rating was too low — could that be the reason this happened? Are there any other possible causes?

...

What did you do.... did you put the black lead on the "-" terminal of the battery and the red lead on the "+" terminal?

In which case you were using your multimeter to 'short' the battery - the red lead is in the 10A socket which is "UNFUSED".  So the current will be the maximum the multimeter can bear without anything melting.  Make it a habit NEVER to put the red lead in the 10A socket unless you are trying to measure a high current and have everything connected correctly.

You can't measure the "current of the battery" using a multimeter alone.  You'd need a suitably rated battery tester for that.  The multimeter could be used to measure the current flowing through something else - like a bulb wired in series - but even at 10A your meter won't tell you anything particularly useful as the cranking current through the starter motor is likely to be much higher than that.

sujsuj

Another interesting thing I noticed today is that the headlight, which used to work when I previously managed to start the mower, is now not turning on at all.

Up until now, I’ve been using the brightness of the headlight as an indicator of the battery's condition. Since the headlight isn’t glowing anymore, could this help point to the root cause?

I've also uploaded a video of today’s attempt to start the mower after charging the battery for two days.

Thanks very much for your help!

sujsuj

https://www.youtube.com/shorts/Or6naJ28Xrk