Check your ground?

 

@patrickifrench

+1 on checking ground wire(s). May be a bad key ignition (cylinder). ... also a chance (more so these days) that the replacement starter/solenoid could be "bad" out of the box.

 

Just because it's clicking the solenoid doesn't necessarily mean the issue isn't in the interlock circuit. More on that later. If it was a valve adjustment/compression release issue, the starter would attempt to crank and literally whine about the excessive load. The fact that it cranks normally on occasion would suggest that this is 100% an electrical issue.

Easiest diagnostic tool to see where the issue lies, is to connect a set of heavy jumper cables. One end on the engine block, the other directly to a cleaned up neg term on the battery. Try the key. If it cranks reliably, then move the jumper cable from the neg terminal on the battery to a clean bolt on the frame. If it still cranks right up, the issue is engine to frame grounding. If it goes back to being dilitary, then it's the battery to frame connection. If bypassing the normal grounding circuit doesn't change the behavior, move on to troubleshooting the positive side.

Use one end of your heavy jumpers on the big terminal on the starter (NOT the solenoid). Make sure it's got firm contact on the starter terminal, then connect the other end directly on the clean/bright battery positive terminal. Sparks will (briefly) fly, the engine should crank. If it does, then the issue lies either in the positive side pixie plumbing or in the interlock circuit. Now, use a smaller (16-10 AWG) jumper wire with alligator clips, one end on that B+ terminal, the other directly to the switch input (or trigger terminal) of the solenoid. If it cranks, then the issue is in the switch/interlock circuit.

Should the above procedure lead you to the interlock circuit, here's the scoop. Everywhere there is a connection, be it a wire terminal, or switch contact points, in the circuit, you have what is called "voltage drop". Just probing the circuit with a test light and a meter, solenoid disconnected, you may get 12+V everywhere and things look hunky dory. With no current flowing in the circuit, the voltage everywhere should match battery voltage. It's only when the system is engaged and moving current will the problem show up. Then you throw a big load on the system, like engine cranking, and your battery voltage drops 2-3V, there's 2-3+V of drop in the interlock and/or start circuit, and all of a sudden you don't have enough current flowing across the solenoid coil to keep it pulled in.

The resolution to excessive voltage drop in the interlock/start circuit will depend on how your Patriot is wired from the factory. Let me know if this turns out to be the issue. Hopefully you found the problem long before getting that far in.

 

Just because it's clicking the solenoid doesn't necessarily mean the issue isn't in the interlock circuit. More on that later. If it was a valve adjustment/compression release issue, the starter would attempt to crank and literally whine about the excessive load. The fact that it cranks normally on occasion would suggest that this is 100% an electrical issue.

Easiest diagnostic tool to see where the issue lies, is to connect a set of heavy jumper cables. One end on the engine block, the other directly to a cleaned up neg term on the battery. Try the key. If it cranks reliably, then move the jumper cable from the neg terminal on the battery to a clean bolt on the frame. If it still cranks right up, the issue is engine to frame grounding. If it goes back to being dilitary, then it's the battery to frame connection. If bypassing the normal grounding circuit doesn't change the behavior, move on to troubleshooting the positive side.

Use one end of your heavy jumpers on the big terminal on the starter (NOT the solenoid). Make sure it's got firm contact on the starter terminal, then connect the other end directly on the clean/bright battery positive terminal. Sparks will (briefly) fly, the engine should crank. If it does, then the issue lies either in the positive side pixie plumbing or in the interlock circuit. Now, use a smaller (16-10 AWG) jumper wire with alligator clips, one end on that B+ terminal, the other directly to the switch input (or trigger terminal) of the solenoid. If it cranks, then the issue is in the switch/interlock circuit.

Should the above procedure lead you to the interlock circuit, here's the scoop. Everywhere there is a connection, be it a wire terminal, or switch contact points, in the circuit, you have what is called "voltage drop". Just probing the circuit with a test light and a meter, solenoid disconnected, you may get 12+V everywhere and things look hunky dory. With no current flowing in the circuit, the voltage everywhere should match battery voltage. It's only when the system is engaged and moving current will the problem show up. Then you throw a big load on the system, like engine cranking, and your battery voltage drops 2-3V, there's 2-3+V of drop in the interlock and/or start circuit, and all of a sudden you don't have enough current flowing across the solenoid coil to keep it pulled in.

The resolution to excessive voltage drop in the interlock/start circuit will depend on how your Patriot is wired from the factory. Let me know if this turns out to be the issue. Hopefully you found the problem long before getting that far in.

Just because it's clicking the solenoid doesn't necessarily mean the issue isn't in the interlock circuit. More on that later. If it was a valve adjustment/compression release issue, the starter would attempt to crank and literally whine about the excessive load. The fact that it cranks normally on occasion would suggest that this is 100% an electrical issue.

Easiest diagnostic tool to see where the issue lies, is to connect a set of heavy jumper cables. One end on the engine block, the other directly to a cleaned up neg term on the battery. Try the key. If it cranks reliably, then move the jumper cable from the neg terminal on the battery to a clean bolt on the frame. If it still cranks right up, the issue is engine to frame grounding. If it goes back to being dilitary, then it's the battery to frame connection. If bypassing the normal grounding circuit doesn't change the behavior, move on to troubleshooting the positive side.

Use one end of your heavy jumpers on the big terminal on the starter (NOT the solenoid). Make sure it's got firm contact on the starter terminal, then connect the other end directly on the clean/bright battery positive terminal. Sparks will (briefly) fly, the engine should crank. If it does, then the issue lies either in the positive side pixie plumbing or in the interlock circuit. Now, use a smaller (16-10 AWG) jumper wire with alligator clips, one end on that B+ terminal, the other directly to the switch input (or trigger terminal) of the solenoid. If it cranks, then the issue is in the switch/interlock circuit.

Should the above procedure lead you to the interlock circuit, here's the scoop. Everywhere there is a connection, be it a wire terminal, or switch contact points, in the circuit, you have what is called "voltage drop". Just probing the circuit with a test light and a meter, solenoid disconnected, you may get 12+V everywhere and things look hunky dory. With no current flowing in the circuit, the voltage everywhere should match battery voltage. It's only when the system is engaged and moving current will the problem show up. Then you throw a big load on the system, like engine cranking, and your battery voltage drops 2-3V, there's 2-3+V of drop in the interlock and/or start circuit, and all of a sudden you don't have enough current flowing across the solenoid coil to keep it pulled in.

The resolution to excessive voltage drop in the interlock/start circuit will depend on how your Patriot is wired from the factory. Let me know if this turns out to be the issue. Hopefully you found the problem long before getting that far in.

That is a great troubleshooting plan. Not trying to be ugly, but I had no idea I would get such a comprehensive plan! I will try this plan soon.

 

Now here is a man that knows how to troubleshoot. Well done.

 

Check the PTO engagement switch for the mower deck. Had one go out on a Scag Liberty and it acted just as you described. You could wiggle the switch and get it to start. The mower thought the deck was “on” and wouldn’t start. Replaced the switch and it fixed the issue.

 

Know what it was?
There is a small ground wire going to the starting solenoid. This connection was loose, causing the solenoid to not be properly grounded. The detailed troubleshooting plan described above can't exactly be performed on these mowers because the starting solenoid and starter are integral. In other words, you can't connect a battery jumper lead straight to the starter. I was dumbfounded when I ran a jumper cable from the positive battery to the starting solenoid terminal and nothing happened. I sat on the ground and looked, and happened to see that the small green ground wire on the back side of the solenoid was loose; pretty lucky. Anyway, I cleaned it and squeezed the electrical connector together tighter, put it back on and it fired right up. I still can't explain how I was able to hear the starting solenoid "click" and it not start, even with this condition, unless, as the guy described above, when load was applied to the starter it made the suspect ground wire connection lose continuity.

(If I spelled loose and lose correctly in all of that, it will be a miracle.)

When I have a problem such as this, I tend to roll it around in my mind and look at the electrical schematics and think. Sometimes it is just better to actually look at your stuff. I guess, there needs to be a balance between these two philosophies.

 

The detailed troubleshooting plan described above can't exactly be performed on these mowers because the starting solenoid and starter are integral. In other words, you can't connect a battery jumper lead straight to the starter.

Kawi engine on this thing? Those mounted solenoids should still have the starter terminal exposed albeit they aren't the easiest thing to hit with the jumper claps. Like pickin' your nose with boxing gloves on.... Clamping a bolt in the jumper clamp makes it into a nice trouble shooting stinger. The starter terminal will be the nut holding a braided bare cable that darts straight into the motor housing.

Kinda uncommon to see a four pole solenoid on a mounted shift-solenoid setup but good on you spotting that loose ground.

 

I’m sure you figured the problem out by now. I’m just curious as to what it was. As I just found a eight or nine year problem I’ve been having intermittently and I just fixed it yesterday. $12 part.

 

Curious as to the remedy as I had similar issue for 8 years lol. Click and no start click 10 times and start no click nothing sometimes start up fine 4-5 times🤷‍♂️🤷‍♂️. Was the FN seat safety switch started 30 times in a row now🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️