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

sujsuj

Please refer to the key positions on the mower—I believe they are self-explanatory. The light comes on at position 2, then turns off at position 3. I recall that when mower  was working properly, the light used to dim at position 4, but I have no evidence to confirm this now. Thanks.

WIAWSNB

sujsuj said:

Please refer to the key positions on the mower—I believe they are self-explanatory. The light comes on at position 2, then turns off at position 3. I recall that when mower  was working properly, the light used to dim at position 4, but I have no evidence to confirm this now. Thanks.

Thanks - so pretty much as S62 guessed.

Everything seems to be 'correct', apart from the 'cranking' bit.

O is off, obvs. 'Light' is headlamp - ditto. (So, the headlamp is always on when running - I presume a safety feature to make folk jump out of the way?).

I is 'ignition', so the engine's running system is powered - the sparkplug and stuff. And crank is crank.

Ok, I'm not surprised now that the headlamp goes off when you first turn the key up to 'I' - I suspect that's intentional, as it means that the 'headlamp' amps are brielfy diverted to the cranking stage instead, until the engine fires up. 

If the engine had fired up successfully, then releasing the key from the 'crank' position would presumably have seen the headlamp light up again, remaining on during running (the mower will have an 'alternator' as well, to keep the battery charged when it's running, and the electrics powered.) 

Sooo, what's the issue? No idea, but first step would be to check the wires and cables as asked before - see where they lead to, and what the connections are at each end - any signs of corrosion or overheating? Especially look for other wires going to the starter motor - there must surely be some thinner ones too?

Then, it'll be starter motor out for bench-testing

Section62

WIAWSNB said:

Ok, I'm not surprised now that the headlamp goes off when you first turn the key up to 'I' - I suspect that's intentional, as it means that the 'headlamp' amps are brielfy diverted to the cranking stage instead, until the engine fires up. 

If the engine had fired up successfully, then releasing the key from the 'crank' position would presumably have seen the headlamp light up again, remaining on during running (the mower will have an 'alternator' as well, to keep the battery charged when it's running, and the electrics powered.)

No, not normally.  As I said in my previous post, the norm is for position 2  (3 by sujsuj's numbering or "I") to be for the engine running but the headlamp off - most grasscutting is done by day without the need for a headlamp, so there's no point using power which can otherwise be saved for engine starting - which usually happens frequently, compared with say a car.  Position 1 (2 by sujsuj's numbering or the headlamp symbol) is provided in case you do want the headlamp on whilst the engine is running.

WIAWSNB said:

Sooo, what's the issue? No idea, but first step would be to check the wires and cables as asked before - see where they lead to, and what the connections are at each end - any signs of corrosion or overheating?

I think the two smaller wires you mentioned yesterday aren't connected to the starter motor but pass behind it.

WIAWSNB said:

Especially look for other wires going to the starter motor - there must surely be some thinner ones too?

As the starter motor is an inertia type with no solenoid it only needs a single terminal.  There is no need for 'thinner' wires as there is nothing to control.  The single terminal is the 'power' to drive the motor, and that is it.

WIAWSNB said:

Then, it'll be starter motor out for bench-testing

I'd strongly advise sujsuj not to remove the starter motor and bench test it.  Doing so is potentially dangerous with a risk of personal injury as well as damage to the motor (and other things).

DIYing things can be good MSEing, but there are limits where (for example) safety is concerned.  Your own comments have made the point that susjsuj lacks some of the required skillset, in particular understanding and precisely following instructions.  It would be unsafe to advise sujsuj to carry out bench testing of this starter motor.

I'd also make the point - in the nicest possible way - that your own knowledge of how this system works is limited (as is mine) and you are guessing - e.g. about how many connections the starter motor has.  If you don't know then you can't safely advise sujsuj.

Furthermore, bench testing isn't necessary and involves risks sujsuj doesn't need to take.  The only test remaining to do can be done with the motor in-situ.  However my advice remains the same - he's done all that is sensible to do on a DIY basis.  The next step (having completed the wiring checks you advised and apparetly still hasn't been done) is to either replace the starter motor, or to get professional help.

Given all that has happened to it in the past the engine could really do with being overhauled by a professional.  Saving money isn't always about doing it yourself or avoiding paying someone to do something.  The life of this engine could be extended (thus saving money) by giving it some TLC now, and it would avoid sujsuj exposing himself to dangers he clearly doesn't understand.

WIAWSNB

Ah, I see. So, once the engine is fired up, you then either release the key to the 'running' positon 'I', or turn it back a click to the headlamp position - and the engine keeps running with the headlamp on? Cool.

If the starter motor is an inertia type - and very good chance it is - then there will be a separate solenoid located somewhere - I hope at least that SS locates this, and checks its terminals.

And everything else - fair do's :-)

sujsuj

I charged the battery for a long duration, and after that, I almost managed to start the mower. Unfortunately, I didn’t get that moment on video as I was expecting it to work. I did record some of the following attempts, but none of them were as close as the first one. This makes me think the issue is mostly with the battery...?

I’m going to charge it again overnight and try starting it in the morning. If I get another promising result/sound, I’m planning to spend around £40 on a new battery.

The only thing that puzzles me is why it’s not working when I try to jump-start it with the car (today i tried jump start again this time use car's earth terminal rather than battery negative terminal). As you’ll see in the video, jump-starting did result in a stronger cranking sound today, but if the issue is with the battery, I don’t understand why the jump start isn’t working. Any thoughts?

Check out the video of the attempts I made after that initial one.

https://youtu.be/qA8p_tTa15w

WIAWSNB

sujsuj said:

I charged the battery for a long duration, and after that, I almost managed to start the mower. Unfortunately, I didn’t get that moment on video as I was expecting it to work. I did record some of the following attempts, but none of them were as close as the first one. This makes me think the issue is mostly with the battery...?

I’m going to charge it again overnight and try starting it in the morning. If I get another promising result/sound, I’m planning to spend around £40 on a new battery.

The only thing that puzzles me is why it’s not working when I try to jump-start it with the car (today i tried jump start again this time use car's earth terminal rather than battery negative terminal). As you’ll see in the video, jump-starting did result in a stronger cranking sound today, but if the issue is with the battery, I don’t understand why the jump start isn’t working. Any thoughts?

Check out the video of the attempts I made after that initial one.

https://youtu.be/qA8p_tTa15w

If you are connecting your jump leads correctly, then your mower would fire up easily when jumped.

Your mower battery clearly ain't 'dead' - it might not be 100%, but it does still have some capacity. So the fact that adding a more-powerful car battery to this makes next-to-zero extra difference, indicates pretty clearly that this is not a 'battery' issue. (Provided you are jumping correctly - and it looks as tho' you are).

So, I would not waste money on a new mower battery.

1) Have you read your Merc's manual on how to jump? Have you followed this to the letter? If not, please do so.

2) have you traced the wire(s) going to the starter motor, especially the thick red one? If not, please do so.

WIAWSNB

sujsuj said:

Another possibility - tho' I think remote - is that the ignition (key) switch is corroded inside. If the 'cranking' position contacts inside are damaged, then that could reduce the current going to the solenoid, making it weak enough to not function correctly once the starter motor draws power.

The reason I think it's unlikely, tho', is that it would be strange for it to be so consistent in its non-functioning; I'd expect corroded/burnt contacts to sometimes work well, sometimes not work at all, and other times go brrrr as yours does.

However, trace these wires, and you'll hopefully find one that also goes to the solenoid, where it'll meet the thick red starter motor cable.

EnPointe

Green_hopeful said:

I am guessing its a petrol mower. Petrol goes off quite quickly. I used to drain my petrol mower for the winter. Vague memory but i think it damages the carburettor. 

petrol  does go 'off' , especially  E10 ...  so  last run before  thewinter lay -up it's best to  switch  the fuel off  run it until is stops and drain  any  fuel left in the tank ...  there are  also rather  more expensive that pump E10   - long life / low  ethanol petrols available for  these use cases 

FreeBear

EnPointe said:

Green_hopeful said:

I am guessing its a petrol mower. Petrol goes off quite quickly. I used to drain my petrol mower for the winter. Vague memory but i think it damages the carburettor. 

petrol  does go 'off' , especially  E10 ...

E10, and E5 will attack certain plastics & rubbers used in fuel lines and carburetors. You need to check that these parts are safe to use with methanol (modern cars are fine, but not all gardening machinery).

If the fuel is left standing, it can gum up jets and small passageways within a carburetor - Have had to strip down a couple and give them a darned good clean... So if you drain the fuel tank, you also need to do the float bowl.

sujsuj

Fantastic news, everyone! 😊

Today felt like Easter all over again — just like a resurrection, my Mountfield mower came back to life too! Remember what I posted yesterday about getting close to starting it? Well, today it finally roared to life! 

Check out the videos I’ve shared.

The only major change I made was keeping the battery on charge for over 48 hours. Before starting (same as yesterday), I pushed the pinion back to its lower position. I also manually rotated the blades — every 4–5 turns it would get stiff (due to shaft?), so I made sure the engine is in the sequence where it rotate easily  before ignition. 

And this time, I made sure to record the moment, because I had a feeling it would work!

Engine Start   

https://www.youtube.com/shorts/FequuR1vCtI

Running 

https://youtube.com/shorts/80Msbh3X0R8?feature=share

Now I just need a dry day to give my overgrown 1-acre lawn a proper cut. It’s well overdue!

Thanks so much to everyone here for the support. Every time I hit a challenge, you all come through with advice and encouragement. You helped me get through it again this time!