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Good battery voltage
Seat, left and right throttle, brake, and PTO/blade switches seem to check OK
Short solenoid to starter and the starter will engage
Cleaned battery terminals

I have seen where there have been posts saying they were checking for voltage drop in the wiring. It seems I may need to do this but I'm not familiar with how to do it. Can someone give me some details about how to check for this?

Are there any computer modules in the wiring that can cause this problem?

I plan to hook a direct ground from the batter to the engine just in case this is a grounding problem. But since the starter fired off immediately with the solenoid short, I don't think this is a problem.

This is really my first problem in 10-11 years with the machine. I guess it was bound to happen. Thanks for any help you can give me.

If you bridge the two posts on the top of the solenoid & the engine cranks that shows the battery , battery ground & starter is OK
If you have only 1 wire at the bottom of the solenoid , check that wire for battery voltage when you turn the key to Start
If yes then loosen the bolt holding the solenoid to the mower and clean around it.
That bolts provides the ground contact to trigger the solenoid .
Over time corrosion gets in and defeats the ground.
If it has 2 small wires at the base then one must be ground and the other must be battery voltage when the mower is in the start condition & key is turned to start .
Ground happens when the brake is on and lap bars out
Power happens when you turn the key

A good solenoid will switch hard enough to jump out of your hand when it activates
To test the single terminal sit the metal base on the battery - then jump from battery + to the trigger wire
Same thing for a 2 wire one only you need 2 wires & 4 hands , the small terminals are not polarity sensitive so either way will work.
Solenoids spark when they switch and over time that spark burns the contact faces .

Bert you are assuming a remote solenoid. I only have a couple Turf Tigers under my wing but both have Kawasaki engines with solenoid shift starters. Now these do use a relay in the starters circuit. The Scag in question here may have a different setup.

As usual on this site the OP did not give us all the equipment. Here we only got the OEM and the series. With Scag and other we need complete model and serial of the unit and the engine make, model, and spec number at a minimum. I can't even look up the correct owners with some this info.

I'm sorry. Here is the model and serial number. The motor is a Kohler with the solenoid on the starter.


Turf Tiger body
Model: STT61V-26CH-EFI
Serial #: K1900995

Kohler Engine. 26.5 EFI
Model: ECH749 - 3043
Serial #: 4408804871
Build Date: 3/27/2014 N11238

Guilty as charged sir

Does this mean that there is a relay in the starter circuit that may have failed? Would this be found in the control panel box that contains the PTO switch, the key switch, and the throttle?

It looks like the bolts that hold the solenoid to the starter have a special "star" head. Is this what needs to be cleaned if the ground for the start is failing?

Those screws require an external Torx socket. Don't know E size off the top of my head as yet to come across them here on a starter.

But to figure what size you need find a matching Torx bit then divide it size by 5 and that will give you the E socket size.

Update: I actually had a Kohler to come with these screws. They are E5 External Torx screws.

https://www.harborfreight.com/14-in...&adsetid=114845773417&product=68017&store=495

Simplefarmer said:

It looks like the bolts that hold the solenoid to the starter have a special "star" head. Is this what needs to be cleaned if the ground for the start is failing?View attachment 64650

Click to expand...

Oh my. Leave those alone.

It's either a mounting bolt or two that mounts the starter to the block or a copper conductor cable going to the frame or even better the - battery post.

Best ground on any vehicle is the - battery post.

I finally have a had a chance to check for voltage on the small ignition wire going to the solenoid. I'm not getting any voltage when the key is turned to start.

Since there is no voltage, do I need to check a relay that was mentioned as possibility in a previous post. I suppose I need to check my starter switch for voltage on the line to the solenoid. I will do that next as I wait for a reply on the possible relay problem. If someone knows where I will find the relay please let me know. Thanks for all the help from everyone.

The starter switch is moving voltage to this "relay" (pictures below). Is there a way to test this relay or should I just replace it?

Below is the relay checked with an ohm meter set to 20 k ohms.

Terminals 2 to 5 is O k ohms
1 to 4 is .08 k ohms

12 volts applied to the small wire (light blue) on the solenoid will engage the starter.

I feel that the relay has something to do with a grounding safety circuit(?). The small wire on the solenoid is light blue and the wires to this relay are red/yel, green/white, and green (2). I don't think it is stopping the voltage to the solenoid unless the module below is checking the ground circuit and when it fails does not apply power to the light blue wire to the solenoid. Maybe someone can clear this up for me.

This is a picture of the module inside the control box that has the key switch, power light, the relay, voltage meter, and throttle.


A light blue wire is present here.

It goes like this
The individual safety switches control the module
The module controls the relay
the relay controls the starter
Some where along the line some thing is not working
Forget about those numbers , I know that this will come as a shock to the calculator generation but the numbers are meaning less
In every case it is works or don't work.

So your next thing to do is get the owners manual which I know your read and kept in a safe place and go to the back, past the parts lists to the wiring diagrams .
Now Scag do nice wiring layout diagrams in full colour . unfortunately yours was done by the MD's grand son so the individual lines are a bit too close together for easy reading so it might be easier to download a fresh copy from Scag's web page then print out your diagram on an A3 colour printer , even if you have to go to a stationary / office supplies shop to have it done .
The one in your owners manual is generic the ones in the back of the parts manual are engine specific .
Check the relay by connecting the trigger terminals directly to you battery.
If it is working you will hear it click and feel it if it is in your hand.
Now make up some short patch leads with a male terminal on each end .
Locate your switches and one at a time pull the plug and jump it with the patch leads according to the wiring diagram
Now you can use your meter and check the individual switches as some will be open and others will be closed when the item ( lap bar for instance ) is in the correct position for starting and from there decide which pair of wires need to be jumped and which pair needs to be left open .
The wiring diagram should actually show that but it does not so you will have to work it out for yourself .

If after you have by passes every switch with your patch leads and confirmed that the module is getting power , the engine does not crank then the module is bad
Usually it is one of the witches or one of the switch plugs as they are more exposed on ZTR's thus more prone to corrosion & mechanical damage .

Relay - will click when voltage applied to the opposing terminals that have the green wires

Bypassing the safety switches (seat, RH and LH lap bars, brake) - all were bypassed and the engine would not crank. I also checked each switch and they showed zero ohms when activated.

I also checked the starter switch and there was a voltage drop on one terminal (white wire) when in the run and start positions. Shown below.
Could a bad starter switch cause the voltage drop and stop the starter from being activated by the solenoid?

Very good link to the Scag website with the manuals and diagrams. Thanks for that.

Scag's web page

I have been thinking that the low voltage on the starter switch could be a sign of a failure of the switch. I will check the switch itself to make sure there is no resistance across the red to white terminals when the switch is set to "run" and "start". If there is resistance, I believe I should either feed a full 12v to the white wire with a jumper to see if that will activate the solenoid and fire the starter, or just get a new switch anyway.

Success! It is now running perfectly. However, the problem was the relay. Even though it was clicking when voltage was applied, there must have been a problem with the contacts. The contacts must have been causing enough resistance to reduce the voltage that would shut down the starting circuit. Imagine that!

Battery OK
Starter would engage with voltage applied
Solenoid would not engage starter (no voltage on the small wire)
LH and RH lap bar switches OK
Brake switch OK
Seat switch OK
Solenoid would engage starter with voltage applied to solenoid control terminal
PTO switch OK
Starter switch OK
Relay assumed OK because of clicking
Begin to believe my electronic module was bad
Replace relay on a whim and everything is working.

Glad she is running again.

If it was the starter relay, I can beleive it. It has a tough life switching all that current every time you crank the engine. It is a must to replace the starter relay when the starter is replaced. This issue is worse in larger engines, more current abuse on the contacts.