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I have an LA120 and it won't start. It has a Briggs and Stratton v twin engine. I have replaced the battery and the starter solenoid. That seemed to have fixed it for a few days, but now it won't start again.

The battery shows 12-14 volts at the terminals at all times. Voltage at the solenoid hot post is 12-14 at first, but then behaves oddly when trying to start. When the switch is moved to the lights position, the headlights come on, voltage is still good. When it is moved to the run position, the voltage at the hot side of the solenoid drops to 0. The voltage at the battery terminal is still 12-14 at this point. If I turn the switch back the lights will no longer come on. After letting it rest off for a while, it goes back to the behavior above.

Could it be the voltage regulator?

stevepainter said:

I have an LA120 and it won't start. It has a Briggs and Stratton v twin engine. I have replaced the battery and the starter solenoid. That seemed to have fixed it for a few days, but now it won't start again.

The battery shows 12-14 volts at the terminals at all times. Voltage at the solenoid hot post is 12-14 at first, but then behaves oddly when trying to start. When the switch is moved to the lights position, the headlights come on, voltage is still good. When it is moved to the run position, the voltage at the hot side of the solenoid drops to 0. The voltage at the battery terminal is still 12-14 at this point. If I turn the switch back the lights will no longer come on. After letting it rest off for a while, it goes back to the behavior above.

Could it be the voltage regulator?

Click to expand...

You can't read voltage across the solenoid terminals when the solenoid is engaged. It would be the same voltage on both terminals.

What if you put a screw driver across the solenoid post when the key is on?
Does it try and start?
If current is going through the solenoid...it should try and start unless the starter is bad.

shiftsuper175607 said:

You can't read voltage across the solenoid terminals when the solenoid is engaged. It would be the same voltage on both terminals.

What if you put a screw driver across the solenoid post when the key is on?
Does it try and start?
If current is going through the solenoid...it should try and start unless the starter is bad.

Click to expand...

Thanks for the reply.

I'm not reading voltage across the solenoid terminals. I'm reading voltage from the negative battery terminal and the hot side of the solenoid. This is why it puzzles me that the voltage drops to nothing there - a mere 3 inch or so wire length from the positive battery terminal at the other end of the wire itself. It does not drop to 0 at the battery terminal however.

This is why I was thinking maybe it's the regulator - there's a thin wire tied into the hot side of the solenoid with the positive battery cable. It goes to a 20 amp fuse (which looks fine) and then on to the voltage regulator on the engine.

I had tried the screwdriver trick and if the mower has been resting as above it'll get a slight jolt as if it's going to crank over but immediately stop. Basically it behaves almost exactly the same as if I try to start it with the key.

stevepainter said:

I have an LA120 and it won't start. It has a Briggs and Stratton v twin engine. I have replaced the battery and the starter solenoid. That seemed to have fixed it for a few days, but now it won't start again.

The battery shows 12-14 volts at the terminals at all times. Voltage at the solenoid hot post is 12-14 at first, but then behaves oddly when trying to start. When the switch is moved to the lights position, the headlights come on, voltage is still good. When it is moved to the run position, the voltage at the hot side of the solenoid drops to 0. The voltage at the battery terminal is still 12-14 at this point. If I turn the switch back the lights will no longer come on. After letting it rest off for a while, it goes back to the behavior above.

Could it be the voltage regulator?

Click to expand...

No it is not the voltage regulator.
The regulator works on the power going back into the battery and only works while the engine is spinning ( generating )

Your problem is the connections between the battery and the mower.
You can confirm this by using some jump start leads from the battery to the engine.
Neg to engine ( I like to use oil drain plug ) Pos to the hot solenoid terminal.

The likley suspect is the grounding bolt to the frame.

Do what Bert recommends but i would also do a load test on the battery. if the voltage drops right off, the only thing that can really cause this is either a bad connection or a bad battery (even a new battery can be bad). your meter is only reading what is called a surface charge. when a slight load is put on, it goes dead very quickly. one of these two things should fix the issue.