If you go to the Scag website, click on manuals, click on STC, scroll down to the Briggs powered models and download the first of the three manuals. In this manual is a colored wiring diagram that makes electrical troubleshooting much easier, you can print the wiring diagram page only. I have printed the electrical components pages along with the wiring diagram and I keep this info with my machine folder.
You have a safety circuit problem and many of the safety circuits have a dual purpose, so you need to trace this thru from a starting point. Several things you may want to check:
The seat switch is a common item and sometimes problematic.
Key switches are know to go bad.
If you machine has an electronic interlock module of either P/N 481808 or 483029 this may be a problem. They have been replaced by P/N 483599. This is a pricey component however all safety circuit inputs go to and from this module. Incorrect troubleshooting of the electrical system can damage this module.
All electrical plug connectors are suspect as they can collect dust.
Let us know how you make out with this machine.
Mad Mackie in CT:biggrin:
2004 Scag Tiger cub 48" STC48A 19KA / Kawasaki engine won't start/won't crank. It is older yet is kept indoors and has about 550 hours. This mower will now start about 1 out of every 40-50 attempts with the key. It SEEMS as if it has gotten worse. Since I've been attempting to troubleshoot it the past few days it used to start on about 2-5 turns of the ignition switch. I am just a very average shade tree mechanic.
Here is what I've checked. I have 12.8-13.0 volts at the battery. I tested the ignition switch per a you tube video? I have continuity and seemingly Checks okay (per the video?) I have 12.8v at the red battery cable at the starter and 0v at the small red wire on that same lug. I have 0volts at the green/white striped wire that is on the spade on the solenoid when it is attached. HOWEVER, With the key to "start" position when the green/white striped wire is removed from the solenoid spade I then have 12.8 volts??? When i touch the wire to the spade I have 0 volts??? Ive ohm'd out the parking brake, lever switches, and seat switch. Fuses are good as well. When turning on the key i can hear/feel the start relay clicking . I can start the mower by jumping the solenoid at the starter. I've went through the flowchart of diagnosis from the scag technical manual. It's lead me faulty wiring or connections. i have continuity and ground from the negative battery to the grounds on the engine/frame the black wire at the module interlock box, and the black wire at the ignition switch...I'm assuming these grounds are okay. I've cleaned/used dielectric grease most of the connections. I have not checked the pto switch but didn't think this was causing an issue as it has worked flawless.
It seems like its an ignition switch as it has gotten worse because i can run and park the mower and it wont start. Nothing on the mower will move and many key turns later it will then start. However the switch tests out okay. and it will switch key on power many consecutive times to the small green/white solenoid wire ONLY when it is unattached from the solenoid spade?
I really don't want to send this to the dealer only to have them guessing while racking up a huge bill. ANY HELP WOULD BE GREATLY APPRECIATED!!!!!!!
At this point in time I have few suggestions and here they are;
The fuel flow in fuel filters is directional, usually there is some indication on the filter as to the direction of flow.
Check the vents in the fuel caps, make sure that they are venting.
Do any fuel hoses run close to a hot part of the engine?
Fuel pumps work on pulses of pressure from the crankcase, is the pulse hose OK and installed correctly?
When the machine is in the full operating condition, brake off, levers in, deck running, the seat switch is the main safety item. I have replaced many seat switches over the years.
Electrical problems appear as a fuel problem and vice versa.
While operating the machine and it wants to die, quickly pull in some choke to see if this carries over and keeps the engine from stopping.
Did you cut the old fuel hoses off with a knife and possibly scratch the hose fittings? Air can leak thru the scratches and the fuel pump can loose suction.
Run a temporary fuel hose directly from one fuel tank to the engine for diagnostic purposes. I have replaced several fuel selector valves over the years, but not many. Some have O rings in them and can deteriorate in time and exposure to ethanol fuel.
Mad Mackie in CT:biggrin::smile:
I have loss of fuel too. Only seems to happen when hot. If I choke it, it will keep running for a bit. Starts right back up but dies, time varies but up to 10 times on one house. Any thoughts. HELP. I replaced fuel pump and vacuum line to pump. No change.
Tada!!!! Thanks MadMackie... it was the starter relay... it was clicking and ticking but obviously wasnt holding in when the starter needed the extra current. At least this will allow me to maintain troubleshooting my "other" issue of intermittently dieing.... I have spark at the plugs and coils when cranking when it dies... I have replaced the fuel pump..cleaned the carburetor. I have also tested the carb fuel shut off valve in the carb bowl. It test out good but I am currently using a metric bolt in the bowl to bypass the fuel shut off valve to see if thats the problem... THANKS AGAIN....
I went and tested all of my switches except the pto switch. However i've never had any issues with the pto engaging whatsoever. Since the relay has been replaced and the machine will now start, I decided to test drive the mower with the hopes that the intermittent dieing would be fixed. So far so good. In fact I'm not sure if it's a mental thing or not but it seems to be running very smooth? I do know a green&black wire does run from the ignition relay that i replaced down to the interlock module wiring connector. At first i didn't think the start relay had anything to do with anything but the starting circuit. Now i'm not so sure??? Actually my intermittent dieing issue has been going on a long long time. Sometimes it won't die at all,, sometimes it will die 6-8 times when cutting. I need to find out more about exactly the green and black wire coming form the start relay to the module does???
2004 Scag Tiger cub 48" STC48A 19KA / Kawasaki engine won't start/won't crank. It is older yet is kept indoors and has about 550 hours. This mower will now start about 1 out of every 40-50 attempts with the key. It SEEMS as if it has gotten worse. Since I've been attempting to troubleshoot it the past few days it used to start on about 2-5 turns of the ignition switch. I am just a very average shade tree mechanic.
Here is what I've checked. I have 12.8-13.0 volts at the battery. I tested the ignition switch per a you tube video? I have continuity and seemingly Checks okay (per the video?) I have 12.8v at the red battery cable at the starter and 0v at the small red wire on that same lug. I have 0volts at the green/white striped wire that is on the spade on the solenoid when it is attached. HOWEVER, With the key to "start" position when the green/white striped wire is removed from the solenoid spade I then have 12.8 volts??? When i touch the wire to the spade I have 0 volts??? Ive ohm'd out the parking brake, lever switches, and seat switch. Fuses are good as well. When turning on the key i can hear/feel the start relay clicking . I can start the mower by jumping the solenoid at the starter. I've went through the flowchart of diagnosis from the scag technical manual. It's lead me faulty wiring or connections. i have continuity and ground from the negative battery to the grounds on the engine/frame the black wire at the module interlock box, and the black wire at the ignition switch...I'm assuming these grounds are okay. I've cleaned/used dielectric grease most of the connections. I have not checked the pto switch but didn't think this was causing an issue as it has worked flawless.
It seems like its an ignition switch as it has gotten worse because i can run and park the mower and it wont start. Nothing on the mower will move and many key turns later it will then start. However the switch tests out okay. and it will switch key on power many consecutive times to the small green/white solenoid wire ONLY when it is unattached from the solenoid spade?
I really don't want to send this to the dealer only to have them guessing while racking up a huge bill. ANY HELP WOULD BE GREATLY APPRECIATED!!!!!!!
New input
from a new member: I had same "no cranking" intermittent problem. I had a 5 year old battery so I replaced it assuming it was bad. Wasn't. I changed the relay with no improvement. Relays can be bought at NAPA for $23.73 in WI. Scag commits rape in selling the relay for $110.00 plus tax. I noticed that when putting my battery charger in "jump Start" mode it would crank every time. I should have caught that sooner as it is a clear sign of poor connectivity. I cleaned all 4 of the limit switch tabs and applied dialectric grease. Same PTO connector. No improvement. Turns out is was corroded tabs on the two fuses. I cleaned and greased them and everything works good now. Thanks to everyone for your input. It was very helpful.
Under the control panel that has the key switch is a relay that is the start circuit main control point passed the key switch. Purchase a Scag replacement for this relay as it had a diode in it. However you can use an auto parts store relay for trouble shooting. Another possibility is the seat switch, but check the relay first.
Mad Mackie in CT