zenith99 0 #1 Posted November 17, 2014 Hi, I've been looking at the forum for help with my starting issue but decided just to post because I'm stumped. We bought this tractor a 90, I think, 520h this summer, it started and ran great. It sat then till a few weeks ago, put a new battery in and it started although ran a bit rough. Next time I tried to start it, it was no go, would try to fire and occassionaly backfire through the carb. So here's what I've done. New plugs and they fire, checked grounded to engine and with a test light. Checked the ignition trigger, it tests ok. The coil tests ok for resistance but when I do the test for voltage I only get 10.5, can that be the problem? I know there's spark but the tractor will not fire even spraying carb cleaner or ether directly in the carb. As I say, I'm stumped. Any suggestions? I need to get this up and running, it has a snowblower and was going to be the main machine this winter. Thanks for any help, Brad in snowy Duluth MN Share this post Link to post Share on other sites
WH nut 553 #2 Posted November 17, 2014 Welcome to the club, Since it did fire then died,and you seem to have spark I would try pulling one plug out and lay the plug grounded to the motor and crank it. Watch for spark and see if she fires. It doesn't take much to flood and since you said it did start and ran rough Im think you have crude in the Carb. Share this post Link to post Share on other sites
zenith99 0 #3 Posted November 17, 2014 I did check for spark and it's got it, that's why I don't understand why it won't fire by spraying directly in the carb. I did take the top of the carb off and spray everything with carb cleaner to no effect. The carb is clean inside. Share this post Link to post Share on other sites
ericj 1,576 #4 Posted November 17, 2014 the best advice i can give you is to down load the onan service manual which i believe is on here for down load and go through it step by step it will tell what to do and how to do it. did you try to run a jumper wire from the battery to the + side of the coil and see if it will fire ? the guide also tells you to try this step. eric j Share this post Link to post Share on other sites
KC9KAS 4,741 #5 Posted November 18, 2014 Good advise about dowloading the manual. Good luck getting your GT going. Share this post Link to post Share on other sites
WH nut 553 #6 Posted November 18, 2014 Watch the spark and try and start it. I have seen them start with one plug when they are flooded. Let her crank a bit and see if she will fart. Also try spaying some carb cleaner in the carb if you doesn't pop after 10 or 15 seconds. Share this post Link to post Share on other sites
Red-Bovine 288 #7 Posted November 18, 2014 Since it backfired through the carb, my guess it puked an intake valve seat. Very common in 520s. Do a compression test. You should get about 110-120 on a good engine. Red Share this post Link to post Share on other sites
zenith99 0 #8 Posted November 19, 2014 OK, so I did a compression test and got 115 on both cylinders, I guess that rules out a valve problem. I've gone throught the checks in the manual and everything is ok except where it says to test the the coil for 12 volts I get 10.5 volts. Does this mean the coil is bad? Kinda frustrated here. Brad Share this post Link to post Share on other sites
ericj 1,576 #9 Posted November 20, 2014 check the 9 pin connector these are known to be a problem and could loose voltage though them eric j Share this post Link to post Share on other sites
motox25 36 #10 Posted November 20, 2014 (edited) It's probably not your coil, back firing at the carb sounds like the timing is off. Mine did this exact thing when I failed to torque down the flywheel completely and it broke the flywheel key which throws the timing off. If you can rule out a fuel issue id pull the flywheel and check it. Edited November 20, 2014 by motox25 Share this post Link to post Share on other sites