eibbed 63 #1 Posted April 4, 2015 (edited) My Toro has a 20 HP Power Plus Twin Cylinder Overhead Valve Design with 663 hours on it. It has not been neglected or abused. I have kept the oil changed and the filters replaced over the years. However last fall while in use, it stopped running. I was able to start it back up, it went for a short distance then stopped again. When I got it into the garage, it would not start. Once it started warming up this spring I tried to start it and had no luck. Then I installed a new battery, insuring that the connections are clean and tight, cleaned the air breather, emptied the gas tank and replaced with fresh fuel, checked fuel line from the gas tank to the fuel line filter, checked the gas cap, replaced the fuel line filter, checked to insure that the fuel pump is pumping fuel to the carburetor, and installed new spark plugs. The spark plugs that I removed were black, especially the one on the right side of the tractor when sitting on the seat. After having tried to start the tractor numerous times since I installed the new spark plugs, I pulled the plug on the right side and it was black like the previous one. . The tractor surges each time I try to start it. However, once it did start, ran for a few seconds, and then stopped. Any and all replies to this post will be greatly appreciated. Thanks, Dave Edited April 4, 2015 by eibbed Share this post Link to post Share on other sites
stevebo-(Moderator) 8,041 #2 Posted April 4, 2015 Start it up and let it warm up until it stops. Once it does, pull the plug, connect the plug to the coil wire and see if it has spark. I would assume your coil/s are bad. 1 Share this post Link to post Share on other sites
woodchuckfarmer 333 #3 Posted April 4, 2015 Black plugs could be to rich. try leaning it down some. Share this post Link to post Share on other sites
shallowwatersailor 3,213 #4 Posted April 4, 2015 Could mice have gotten to it last year? The coils are under the shroud, which helps to invite them in. The choke isn't stuck by chance? Share this post Link to post Share on other sites
gwest_ca-(File Mod) 10,503 #5 Posted April 4, 2015 Kohler service manual Garry Share this post Link to post Share on other sites
JackC 616 #6 Posted April 5, 2015 It appears to have spark and the fuel pump appears to be pumping. If you use ethanol fuel, for about $100 I would replace the carburetor. You could also try cleaning the carburetor but a rebuild kit is expensive. There is also a shut off solenoid on the carburetor which may be malfunctioning. Share this post Link to post Share on other sites
redtractorfan 13 #7 Posted April 6, 2015 JackC, you're right, I've also heard more than once that the solenoid on the 520s will malfunction. I would check that out as well. Share this post Link to post Share on other sites
mey030 9 #8 Posted April 8, 2015 The Kohler v twin engines had lots of coil issues in the early years. they used an unshielded transistor and any kind of RF interference would blow the transistor the ignition coil numbers would end in - 01 - 02 etc. Check the numbers on the ignition coils if they are not an old 3 check with your dealer 01 and 02 I know for sure were issued with the bad transistors. the city of Bloomington Illinois had 8 walk behind Toros they kept blowing the coils found out it was the handheld FM radios they used. The -03 series coils cued the problem. 1 Share this post Link to post Share on other sites
mey030 9 #9 Posted April 8, 2015 One thing I forgot in my post. these Coiles can be bad and still have spark not enough and not timed correctly. Kohler even came out with their own spark tester looks like a spark plug with a alligator clip and if you look at the bottom looks like A flange nut pressed into the bottom of the plug surrounding the center core Share this post Link to post Share on other sites
Forest Road 594 #10 Posted April 9, 2015 Sounds similar to what I went through. Turned out to be the fuel pump. My dealer had a Kawasaki fuel pump, identical to Kohler, for 1/2 price of a Kohler. Haven't had a problem since. Sent from my iPhone using Tapatalk Share this post Link to post Share on other sites
eibbed 63 #11 Posted April 19, 2015 (edited) Thanks again for all of the comments toward helping me get the motor running again. I have now replaced the fuel pump with a new one, replaced the fuses, had the carburetor fuel shut off solenoid tested, and had the carburetor boiled out at a local Toro dealers shop. Previously when I checked for spark, on both sides, the color was a pinkish yellow. Shouldn't it have been blue? Also, I did get it to barely run. If I hold the choke shut and my wife holds the governor linkage toward the front of the mower, it will barely run. If I try to open the choke, it will stop immediately. I have no idea what this means. Just sharing the information in hopes someone can use. Dave Edited April 19, 2015 by eibbed Share this post Link to post Share on other sites
eibbed 63 #12 Posted May 4, 2015 I hooked up the trailer and backed it up to the garage (after a few tries) and was getting ready to load the mower and take it into a repair shop, but I couldn't concede just yet. I did not pull the ignition coils, but I read on line that my engine has the coils that end in "01". Not good. I am not quite ready to replace them just yet. I found a phone number on line for Kohler Engines Customer Service and spoke with a service technician. After I told him what all I had previously done, he had me first check compression on both cylinders. They were both 155 lbs, which he said is good. Per his suggestion, I then sprayed starter fluid into the carburetor and it started and kept running as long as starter fluid was kept spraying. He doesn't think that I am getting fuel to the combustion chambers. And even though I had the carburetor boiled in an ultrasonic machine, he recommends I purchase a new one. I think I will. Well, that's the latest. I hope I can report that she's up and running soon! Dave Share this post Link to post Share on other sites
eibbed 63 #13 Posted May 6, 2015 (edited) Gentlemen, My new carburetor arrived this afternoon with three gaskets. I can easily see which gasket goes between the carburetor and the air breather. The other two I presume go between the bottom of the carburetor and the engine block. One is thin and the other is about 1/8" thick. Which one goes against the block and which one goes against the bottom of the carburetor? Dave Sorry, I couldn't wait for a response to the gasket placement, I was anxious to install the new carburetor. The thin gasket went next to the engine block and the thicker spacer went next to the base of the carburetor. I hope this was correct. Unfortunately the engine still only surges a little when I try to start it.. Edited May 6, 2015 by eibbed Share this post Link to post Share on other sites
boovuc 1,090 #14 Posted May 6, 2015 The holes between the top and bottom of the carb should be different so after you have the old carb off, you should be able to see where the different gaskets go. You can also look at the old gaskets and determine where they were located. Some times a carb had different uses so a gasket or two in a kit may not be needed and you only need to match the gasket that came off your motor. Share this post Link to post Share on other sites
Rick_in_CT 156 #15 Posted May 7, 2015 Does the engine still seem to fire when you use the starter fluid spray? If it does, then it would appear that you are not getting fuel delivered to the engine via the carb. There is a fuel shut off solenoid mounted in the base of the carb, with a wire attached to it. Did the new carb come with the solenoid or did you have to transfer it to the new carb? Do you know if the fuel shut off solenoid is working? When you turn the key on to the run position, you should get 12vdc from the end of the solenoid where the wire attaches to it, and to ground on the chassis. If you don't have 12v at the solenoid, we have an electrical/wiring problem. The 12v pulls the solenoid pin into the solenoid body, and allows fuel to flow into the carb. You may be able to feel the pin pull in with your hand on the solenoid when you turn the key. If you do have 12v at the solenoid, but the plunger is not moving, then the solenoid may be stuck or bad. The solenoid can be bench tested using 12v, and you can see the pin move. Let me know if you need any support in testing the solenoid if you want to go in that direction. Positive 12vdc gets connected to where the wire is attached to the solenoid, and the body of the solenoid has to be connected to the negative, or ground. If testing with the solenoid removed from the carb, make sure all of the gas is out of the solenoid so you don't have a chance for flame/fire if you make a spark connecting test leads. Also make sure that the fuel tank shut off valve is open. You stated earlier that the fuel pump was working. How was this tested? If you can provide feedback to the above, we will see where that takes us. Rick Share this post Link to post Share on other sites
baerpath 517 #16 Posted May 7, 2015 http://outdoorpowerinfo.com/repairs/kohler_command_v-twin_nikki_carb.asp might help 1 Share this post Link to post Share on other sites
doc724 924 #17 Posted May 7, 2015 So here is my 2 cents on all that I have read. I also have a 520 i and it (used) to not start after a hot shutdown. I did many of the above things that were suggested including a thorough electrical check of base line resistances through all the various relays in the start circuit. I finally did change the fuel pump. Did it correct it? Don't know as I got so paranoid, I would never shut if off hot if I needed it again that same day. Two days ago, I did do a hot shut down and 30 minutes later it started just fine. I also tried the gas in the spark plug hole and it ran fine which tells me that you have a fuel problem, not a spark problem. The fuel solenoid shutoff is not getting power during the start cycle. Check all the wiring in the start circuit which provide 12v to this solenoid. The start relay could be the problem or any of the electrical contacts in the start relay circuit. A high resistance at a connector may behave like an open circuit. Any place there is an electrical contact can be suspect, including the ignition switch. Swap the 3 relays around, they are identical. Sometimes just moving the connector on and off is enough to to wipe off any oxide that may have developed. On another note, the thick gasket is a heat isolator. Don't know if you need it or not. It was a frequently used item on auto engines in the 80's to keep heat from the block from getting to the carb and causing vapor lock. Electrical problems require diligence, patience, a wiring diagram and a good multimeter to diagnose. I don't envy you, but there is no other way around it. 2 Share this post Link to post Share on other sites
eibbed 63 #18 Posted May 8, 2015 The holes between the top and bottom of the carb should be different so after you have the old carb off, you should be able to see where the different gaskets go. You can also look at the old gaskets and determine where they were located. Some times a carb had different uses so a gasket or two in a kit may not be needed and you only need to match the gasket that came off your motor. Hi boovuc, You are right. As soon as I lifted the carburetor off of the engine, I saw the thick diamond shaped gasket. Anyway I have already installed the thinner gasket below the thick one and hope it causes no harm. Thanks, Dave Share this post Link to post Share on other sites
eibbed 63 #19 Posted May 8, 2015 (edited) Does the engine still seem to fire when you use the starter fluid spray? If it does, then it would appear that you are not getting fuel delivered to the engine via the carb. There is a fuel shut off solenoid mounted in the base of the carb, with a wire attached to it. Did the new carb come with the solenoid or did you have to transfer it to the new carb? Do you know if the fuel shut off solenoid is working? When you turn the key on to the run position, you should get 12vdc from the end of the solenoid where the wire attaches to it, and to ground on the chassis. If you don't have 12v at the solenoid, we have an electrical/wiring problem. The 12v pulls the solenoid pin into the solenoid body, and allows fuel to flow into the carb. You may be able to feel the pin pull in with your hand on the solenoid when you turn the key. If you do have 12v at the solenoid, but the plunger is not moving, then the solenoid may be stuck or bad. The solenoid can be bench tested using 12v, and you can see the pin move. Let me know if you need any support in testing the solenoid if you want to go in that direction. Positive 12vdc gets connected to where the wire is attached to the solenoid, and the body of the solenoid has to be connected to the negative, or ground. If testing with the solenoid removed from the carb, make sure all of the gas is out of the solenoid so you don't have a chance for flame/fire if you make a spark connecting test leads. Also make sure that the fuel tank shut off valve is open. You stated earlier that the fuel pump was working. How was this tested? If you can provide feedback to the above, we will see where that takes us. Rick Hi Rick_in_CT, Yes the engine still seems to do fine when I use the starter spray. Yes, the new carburetor came with a new solenoid. No, I do not know if the fuel solenoid is working. My next door neighbor who has the equipment and knows how to check the wiring is coming over this weekend to give me a hand. I will ask him to check for 12v power to the fuel solenoid. To check my fuel pump, I disconnected the fuel line from the pump to the carburetor and cranked the engine. It spit gas into a bowl. doc724 has suggested a number of electrical issues that could be causing my engine not to start. I will ask my neighbor to look into them also. Edited May 8, 2015 by eibbed Share this post Link to post Share on other sites
baerpath 517 #20 Posted May 8, 2015 Check the motor ground Share this post Link to post Share on other sites
eibbed 63 #21 Posted May 8, 2015 So here is my 2 cents on all that I have read. I also have a 520 i and it (used) to not start after a hot shutdown. I did many of the above things that were suggested including a thorough electrical check of base line resistances through all the various relays in the start circuit. I finally did change the fuel pump. Did it correct it? Don't know as I got so paranoid, I would never shut if off hot if I needed it again that same day. Two days ago, I did do a hot shut down and 30 minutes later it started just fine. I also tried the gas in the spark plug hole and it ran fine which tells me that you have a fuel problem, not a spark problem. The fuel solenoid shutoff is not getting power during the start cycle. Check all the wiring in the start circuit which provide 12v to this solenoid. The start relay could be the problem or any of the electrical contacts in the start relay circuit. A high resistance at a connector may behave like an open circuit. Any place there is an electrical contact can be suspect, including the ignition switch. Swap the 3 relays around, they are identical. Sometimes just moving the connector on and off is enough to to wipe off any oxide that may have developed. On another note, the thick gasket is a heat isolator. Don't know if you need it or not. It was a frequently used item on auto engines in the 80's to keep heat from the block from getting to the carb and causing vapor lock. Electrical problems require diligence, patience, a wiring diagram and a good multimeter to diagnose. I don't envy you, but there is no other way around it. Thank you for your words of encouragement. With the help of my next door neighbor, this weekend I will address the possible wiring solutions you have suggested. Dave Check the motor ground Thanks, I did. A couple of times. Dave Share this post Link to post Share on other sites
eibbed 63 #22 Posted May 8, 2015 (edited) http://outdoorpowerinfo.com/repairs/kohler_command_v-twin_nikki_carb.asp might help Thanks, I found the site to be extremely informative with great photographs. Pictures help alot. Dave Edited May 8, 2015 by eibbed Share this post Link to post Share on other sites
eibbed 63 #23 Posted May 13, 2015 (edited) Gentlemen, My neighbor came over the past two nights and checked wiring on my mower. We swapped the three relays around and cleaned the connections. We removed the starter and cleaned the connections. It was showing some corrosion, but is clean now. We checked the voltage from the battery to the fuel solenoid wire on the tractor and got only 8&1/2 volts. When we ran a wire from the battery and touched it to the fuel solenoid wire on the carburetor we could hear it click and feel it opening and closing. We then clamped a temporary wire from the battery to the fuel solenoid wire on the carburetor and the engine started and ran good. The wiring from the engine disconnect up to the fuel solenoid he thinks is good. We found two diodes in that same wiring. Is there a way to check and see if the diodes are working properly? We are going to test the wires back to the starter tomorrow evening. Oh, I was going to remove some of the shroud concealing the wires running up to the fuel solenoid, but it soon looked like the engine may have to be removed for me to get the shroud off. I hope there is a better way. If so, please let me know. She's not running yet, so if there are any suggestions I have overlooked or any new ones, please let me know. Thanks all, Dave Edited May 13, 2015 by eibbed Share this post Link to post Share on other sites
Rick_in_CT 156 #24 Posted May 14, 2015 The diodes can be tested using an ohm meter. Diodes only permit current to flow in one direction. Some multi-meters have a diode test function, while most all have the ohm reading function. With the ignition off (you don't want power in the circuit when testing the diode), set the meter to diode test or ohms, and put one probe on each side of the diode. With the meter across the diode, you will either get a reading of full continuity (just like touching the two meter probes together), or you will have no continuity. Which ever reading you get, continuity or no continuity, make a note of it. Now reverse the meter leads, if the red probe was on the right side of the diode for the first test, now move it to the left side of the diode with the black probe on the right. If the diode is good, you should not get a reading that is totally opposite of what you got in the first test. If you previously had no continuity, now you should have full continuity, or vise versa. The meter is attempting to put a small current through the diode, but if the diode is working as it should, it will block the flow in one direction. Repeat the same test on the second diode. Any results that are different than described would indicate a failed diode, such as no continuity indicated with the probes in either of the two possible configurations. A failed diode will stop the Kohler in its tracks. If you find a bad diode or two, they will need to be replaced. Before removing them, you need to look very closely at them, looking for a stripe on the body of the diode. The stripe indicates the orientation of the diode, and the new diode MUST be installed with the stripe positioned just as the original, either going towards the solenoid or away. Make a note of the stripe position, or take pictures. The diodes can be soldered into the harness. It is best to cover them with heat shrink tubing if you have access to it. Many auto parts stores have heat shrink tubing, as well as home depot in the electrical department. A local Kohler dealer may have the diodes, not too uncommon that they fail. I have read that they fail due to a high voltage spike getting onto the system from the PTO clutch. Kohler actually makes a kit using more diodes to block the PTO from doing this. Let me know if you need more support. Rick 1 Share this post Link to post Share on other sites
doc724 924 #25 Posted May 14, 2015 I happen to be sitting next to where I store my tractor manuals. I have previously done the resistance checks mentioned by Rick and saved the results. Using a multi meter in the forward bias direction (black probe on the striped end of the diode), diode resistance measured 120 ohms on both diodes. Reverse bias (red probe on the striped end) was infinite resistance (total blocking of current) as it should be. Also, as a point of reference, the solenoid coil resistance is 40 ohms. 1 Share this post Link to post Share on other sites