solenoid clicks but no crank

[sky jumper]

Diodes are used in properly designed solenoid (or relay) circuits to bleed excess current when the the field (solenoid coil) collapses. They are also used in circuits to allow current to flow only in one direction not allowing the current to back feed into a circuit.

There is only one starter solenoid and one solenoid relay. When you activate the start switch arre you sure you are hearing the starter solenoid or are you hearing the solenoid relay? If you are hearing the starter solenoid then the solenoid relay (5) is working properly (along with all the other interlock switches everyone is asking you to check.

If you are hearing the solenoid click then all the circuits are working correctly which points to a wiring or connection problem from the battery through the solenoid and to the starter. Or a bad (new) solenoid.

I'm hearing the solenoid click, not the relay (5). I can feel it. so I agree relay (5) is closing and those other switches are fine. the solenoid tests fine when the coil is connected directly to the battery the contacts close and ohm out at ~0.

the problem is not enough current in the solenoid coil circuit. something is limiting it. shorted it with a DC ammeter and got 0.5A. should've blown the fuse.

could relay (5) contacts be adding enough resistance to limit the current? or that diode? I can't find the diode I have a bad feeling its not user accessible.

 

[MParr]

Try this. Remove the connector at the seat safety switch. Make a jumper for the connector. Turn the key to run and check for voltage at all of the other safety switches, brake switch, pto switch, relays, fuses and solenoids. When doing this, make sure that your motion handles are in the neutral position and the parking brake is on. Could the clicking that you are hearing be coming from one of the relays?

 

[Trav]

My belief is that the fault is going to be found in the brake switch or motion control switches.

It looks the the starter is a single cable, how did you confirm the starter itself is good, did you hook a 12v cable (jumper cable will work) momentarily to the main terminal on it? Did you check the battery itself?
I agree it probably is in some sub circuit but I would want to know the starter and battery are okay before getting out DVOM and embarking on a goose chase.

 

[sky jumper]

the clicking is 100% definitely coming from the solenoid, not one of the relays. to start the mower I jumped the solenoid contacts with big wrench. mower fired right up ran fine. and again the solenoid itself is fine.

 

[ka9mnx]

From what you are saying, there is plenty of voltage at the solenoid to turn/start the mower. Check the voltage drop at the solenoid contacts from the ignition key. If the voltage stays at 12v when you turn the key to start, you have a bad solenoid. If the voltage drops to near zero, wiring or relay from the starter key switch to the solenoid is bad.

 

[sky jumper]

From what you are saying, there is plenty of voltage at the solenoid to turn/start the mower. Check the voltage drop at the solenoid contacts from the ignition key. If the voltage stays at 12v when you turn the key to start, you have a bad solenoid. If the voltage drops to near zero, wiring or relay from the starter key switch to the solenoid is bad.

I believe the solenoid coil voltage stayed at 12V while attempting to crank. the coil measures 3.2ohms. so I figure there should be about 3-4 amps flowing through the coil, but when I measured it I only got 0.5-0.8 amps (it jumped around, which I thought was odd).

so thinking this through, with 12V at coil terminal and only 0.5A flowing through it, there must be an extra 14ohms between the coil and ground somewhere. Relay (5) is the only thing in that ground path --- so perhaps its contacts are pitted?? I'll pull it and ohm it.

 

[mk378]

Relay 5 is more than just the solenoid. Relay 5 must be energized both to ground the starter solenoid coil and the PTO clutch, and to unground the ignition so the engine can continue to run. Also the same circuit that energizes relay 5 energizes the fuel cut solenoid so the engine can continue to run.

There are two paths to energize relay 5. It starts on the right side of the page.

Circuit 1 is through relay 9 (which I'll call the not starting relay) and the seat switch. If the key is on (but not start), and the seat is occupied, battery voltage can flow through the wire to the left side of the brake switch. From there if either both handles are in neutral or the brake is not applied, relay 5 is energized and the engine will continue to run.
In summary
Key is on (7)
5A fuse is good
and key is not turned to start (9)
Seat is occupied (10)
Both handles in neutral (14, 15)
... or brake is not applied (12)

Circuit 1 lets the machine run normally. If the operator leaves the seat, or moves a drive handle out of neutral without releasing the brake, relay 5 will de-energize, which stops the engine and de-energizes the PTO clutch. Because of relay 9, circuit 1 is inactive for trying to start the engine. Turning the key to start energizes relay 9, which opens circuit 1.

Circuit 2 enforces the interlock conditions necessary for starting:
Key is on or start (7)
5A fuse is good
PTO is not on (11)
Brake is applied (12)
Both handles in neutral (14, 15)

This circuit is for starting. Additionally, the seat must be occupied to have a path from the key to the high side of the starter solenoid.

So as the machine continues to run on circuit 1, look at things unique to circuit 2: the not on part of the PTO switch, and the not applied circuit of the brake switch.

Note you can bypass all of that to test relay 5 by jumping battery voltage to the coil of relay 5. Then the starter should turn when the key is turned to start, the only other condition would be interlocks on the high side of the starter solenoid meaning the seat must be occupied.

 

[zrxkawboy]

How exactly are you measuring current?

 

[sky jumper]

How exactly are you measuring current?

with a dmm across the solenoid coil wires while disconnected from the solenoid and my son in the seat turning the key to start. was trying to determine how much current the solenoid wire from the key switch would deliver. its fused 5A. I figured my dmm would basically short it out and blow the fuse. nope, 0.5-0.8 A. fuse is still good.

 

[MParr]

A quick check of the PTO switch will confirm if there is a problem there. With the seat safety switch jumped, turn the key to run and pull or twist the PTO switch. Do you hear a click at the PTO clutch? If not, you have a bad PTO switch and that will result in a no start condition. The parking brake must be off and the motion control levers must be moved inward. NOTE: Please make you a jumper wire to bypass the seat safety switch. This will allow you proceed without any help.

 

[jhs914]

A quick check of the PTO switch will confirm if there is a problem there. With the seat safety switch jumped, turn the key to run and pull or twist the PTO switch. Do you hear a click at the PTO clutch? If not, you have a bad PTO switch and that will result in a no start condition. The parking brake must be off and the motion control levers must be moved inward. NOTE: Please make you a jumper wire to bypass the seat safety switch. This will allow you proceed without any help.

This. As I noted in an earlier reply a faulty PTO switch was the cause of a non-start in my zero turn. I checked everything you have a checked (safety switches, battery, solenoid, etc.) and replacing the PTO switch solved the problem.

 

[sky jumper]

...So as the machine continues to run on circuit 1, look at things unique to circuit 2: the not on part of the PTO switch, and the not applied circuit of the brake switch.

Note you can bypass all of that to test relay 5 by jumping battery voltage to the coil of relay 5. Then the starter should turn when the key is turned to start, the only other condition would be interlocks on the high side of the starter solenoid meaning the seat must be occupied.

that was a really good breakdown of how this all works.

I guess my one thought is if either the brake or PTO switches were malfunctioning relay (5) would not close at all, and I'd get no clicking at the solenoid. since the solenoid is being at least partially energized can't I conclude that both the brake & PTO switches are fine?

I do suspect the contacts of Relay (5) might be corroded/pitted etc and maybe that's why the current through the solenoid coil is impeded. I will test that theory asap.

 

[mk378]

I wouldn't put a lot of faith in any clicking that might be heard. Relay 9 will click in each time the key is turned from on to start. Relay 5 will click out when the key is turned from on to start if the brake switch or the PTO switch are not allowing circuit 2 to operate.

Note that there are different types of solenoids that look the same on the outside, but are wired differently inside. Be sure your new solenoid is the correct type. If you connect a battery to the two small posts and nothing else, it should snap in and close the circuit between the two big posts.

Then back on the machine measure voltage between the two small posts while trying to start.

The same contact in relay 5 that grounds the solenoid coil also grounds the PTO clutch, which takes a lot more current. With the key in the on position you should be able to start the engine by crossing the two big posts to directly run the starter. Confirm that the interlock logic for circuit 1 operates properly, including the PTO clutch. With the key in the start position you should also be able to start the engine by crossing the big posts. If it cranks but does not start (but will start in the run position) that means that relay 5 is de-energized due to a problem in circuit 2.

 

[jhs914]

A quick test of the PTO switch is easy and will confirm or eliminate the switch as the source of your problem. Here is how:

 

[MParr]

I will agree with some others. The starter solenoid needs to be a close representation of the original part or an OEM part. A solenoid can still be bad even if you can jump it with a screwdriver or other tool and the mower starts. The inner workings may not be functioning correctly. Do you have a test light? Those things are really useful in this type of situation.

 

[MParr]

@sky jumper
Any updates on your quest to locate the gremlin?

 

[sky jumper]

not really. the PTO is fine. the solenoid *contacts* ohm open when it clicks in circuit, but ohm closed when the coil is connected straight to battery. I'm going to replace relay 5 just haven't gotten around to it yet looking at options to use generic $3 relay as opposed to $100 kubota part.

edit - meant to say *solenoid contacts ohm open*

 

[mk378]

Set all the interlocks to allow starting: PTO not on, brake applied, both handles at neutral, seat occupied.

Turn the key to start and hold it there. While holding the key, jump the solenoid contacts with a wrench. It is important that you're holding the key at start here so that the circuit 2 will energize relay 5.

If you have the key at on, circuit 1 will energize relay 5, which will allow it to start, but is not representative of trying to start with the key.

Does it start, or crank and not start?

IF you get a crank but not start, circuit 2 is not working, which is most likely the seat switch or the brake switch. Note that there are contacts in these switches that are only used for the circuit 2 interlock. The PTO switch may turn the PTO on and off OK, but the other circuit through the switch (which allows starting only when the PTO is not on) could be bad.

Relay 5 is not bad if the circuit 1 functions work. Make sure the PTO works, this is the same contact in relay 5 that works the solenoid. The PTO should drop out and the engine should kill if you move the drive handles out of neutral with the brake on, or leave the seat.

 

[mk378]

solenoid coil ohms open when it clicks in circuit, but ohms closed when the coil is connected straight to battery

I'm not sure what you tested there. In the circuit (with all interlocks set for starting, and the key turned to start), with the (-) of the meter on ground, you should measure close to battery voltage on one solenoid terminal. and close to ground on the other.

Out of circuit you should have a few ohms resistance between the two small solenoid terminals, with no path to ground or to the big terminals. When a battery is connected to the two terminals it should snap closed.

 

[sky jumper]

Set all the interlocks to allow starting: PTO not on, brake applied, both handles at neutral, seat occupied.

Turn the key to start and hold it there. While holding the key, jump the solenoid contacts with a wrench. It is important that you're holding the key at start here so that the circuit 2 will energize relay 5.

If you have the key at on, circuit 1 will energize relay 5, which will allow it to start, but is not representative of trying to start with the key.

Does it start, or crank and not start?

IF you get a crank but not start, circuit 2 is not working, which is most likely the seat switch or the brake switch. Note that there are contacts in these switches that are only used for the circuit 2 interlock. The PTO switch may turn the PTO on and off OK, but the other circuit through the switch (which allows starting only when the PTO is not on) could be bad.

Relay 5 is not bad if the circuit 1 functions work. Make sure the PTO works, this is the same contact in relay 5 that works the solenoid. The PTO should drop out and the engine should kill if you move the drive handles out of neutral with the brake on, or leave the seat.

it starts and runs fine in the scenario you describe (key at start, jump solenoid contacts with wrench).

I agree relay 5 is at least functioning, insofar as it is ungrounding the ingition coil. so the brake, PTO, and motion levers are working. otherwise it wouldn't run at all. I guess my theory is relay 5 is impeding current flow through the solenoid coil.

at the moment I can't test that theory because I have the key switch disassembled to clean the internal contacts, and I'm having trouble getting it back together (goofy springs and steel balls inside).