cod 116 #1 Posted February 20, 2019 Out clearing the snow and the 418 is running fine. All of a sudden with the pto engaged, the engine starts to run rough and loses power acting like it's running out of gas. I disengage the pto and that helps smooth the engine out but it doesn't solve the problem. I can see gas flowing through the filter and I opened the gas cap in case the was a vent problem. Nothing seemed to help so I nursed it back to the garage with the throttle half open and the choke just about closed. I took off the air cleaner housing and cleaned all of the linkages for the carb and governor and that seemed to help as I could run it with no choke full throttle and it ran smoothly until I tried to back it into the garage and the roughness came back. So as I don't need the beast at the moment, I am looking for suggestions on things to check because up till now it's run fine and I don't have a clue as to what might be causing it. Share this post Link to post Share on other sites
peter lena 8,081 #2 Posted February 20, 2019 sounds like a fuel issue, last time you used fuel additive? or cleaned the carb jets? ever use SEAFOAM? gas treatment . usually a fuel / jet issue shows itself under load , like you have. you also might check your safety interlocks, I had some bad fuses causing issues, replaced fuses , used dielectric grease at contact points. those jets are easy to clean out with bread wrapper twist tye wire. just some ideas that have worked for me , good luck ,pete 4 Share this post Link to post Share on other sites
520HC 207 #3 Posted February 20, 2019 Have you got your air cleaner intake in the winter position? The snorkel should be over the hole by exhaust. It heats the air going into the intake, keeps it from frosting up. 3 Share this post Link to post Share on other sites
pfrederi 17,164 #4 Posted February 20, 2019 You sure about your spark plugs/ wires you may be running on one cylinder. Do you have a spark tester? You say PTO so I assume blower. That blowing snow snow can get on the wires melt and then no spark 2 Share this post Link to post Share on other sites
cod 116 #5 Posted February 20, 2019 29 minutes ago, 520HC said: Have you got your air cleaner intake in the winter position? The snorkel should be over the hole by exhaust. It heats the air going into the intake, keeps it from frosting up. Yes the snout on housing is over the exhaust port so hopefully it's getting plenty of warm air. 1 Share this post Link to post Share on other sites
cod 116 #6 Posted February 20, 2019 5 minutes ago, pfrederi said: You sure about your spark plugs/ wires you may be running on one cylinder. Do you have a spark tester? You say PTO so I assume blower. That blowing snow snow can get on the wires melt and then no spark Didn't think of that at the time but I was using a blower and the front plug can get a dusting of snow. I'll have check that when I get into some of Pete's suggestions. Thanks! 1 Share this post Link to post Share on other sites
moe1965 722 #7 Posted February 20, 2019 Just for kicks spray w d 40 on the plug wires . It might be a bad wire. 2 Share this post Link to post Share on other sites
Rob R 951 #8 Posted February 21, 2019 Agree with above be sure to eliminate spark issue(s) and then move to fuel delivery and carb. I can't tell you how many times I have chased the rabbit down the wrong hole.... p.s. a LOT of times it is impossible to tell the difference... run don't walk from anyone who tells you different.... just saying..... also chk the fuel delivery when and if you get there from the tank all the way to the carb and replace any suspect old rubber lines they have a tendency to flake internally due to the high ethanol fuel level. 2 Share this post Link to post Share on other sites
squonk 38,980 #9 Posted February 21, 2019 I had a C125 that had a bad connection in a main fuse. Fuse would get hot but not blow an fuse holder started to melt. I thought for sure it was fuel and just happened to notice the blackened fuse holder when checking the fuel line. Tractor ran fine then would bog down spit and sputter.. 3 Share this post Link to post Share on other sites
953 nut 51,861 #10 Posted February 21, 2019 44 minutes ago, squonk said: had a bad connection in a main fuse. If this was a battery ignition it could well be a fuse, but it is a magnum. Is the oil level good, think there is a low oil switch to protect the engine. Share this post Link to post Share on other sites
squonk 38,980 #11 Posted February 21, 2019 24 minutes ago, 953 nut said: If this was a battery ignition it could well be a fuse, but it is a magnum. Is the oil level good, think there is a low oil switch to protect the engine. True. Another issue I had was a chafed mag grounding wire on a 704 cutting out the ign. I would get a cheap inline spark tester ( Napa) and run the engine. If the spark stays strong during the poor running, then you can look at the fuel system. 2 Share this post Link to post Share on other sites
cod 116 #12 Posted February 24, 2019 Quick follow up as I went out the other day and fired the 418 up. It started right away and idled fine. When it warmed up I could raise and lower the RPM's smoothly. I then removed the front plug wire and the idle got rough so I put it back on and then did the same with the rear plug wire. Now I suspect things dried out so I can't say for sure if it was the plug wires but I also cleaned the carb jets, put on a new gas filter and dumped in a healthy shot of Lucas gas treatment. So far everything seems to be back to normal but later this spring I'll pop the engine covers out and give the engine a through cleaning. I also wonder if it is possible to replace the plug wires without replacing the ignition module as they are old ( I think the 418's came out in 86 or 87) and although I recovered them with heat shrink tubing, it might be time get new wires. So thanks again for the replies - Cod 2 Share this post Link to post Share on other sites
cod 116 #13 Posted April 29, 2019 A quick update as I think I finally figured out the cause of the problem was crud in the gas tank. Finally had a chance to run it for more than 15 minutes and sure enough the roughness came back. As there was barely any gas flowing through the filter, I opened the gas cap to see if that would help and noticed that there were floaters hovering around the small shutoff filter. Using a long screwdriver I gently tried to clean the screen and sure enough the flow picked up again. I was able to run the tank dry, pulled the shutoff out and cleaned the inside of the tank. There was a thin film of gunk on the screen that I was able to remove and once the tank was flushed out and dried, I put it all back together, filled it up with ethanol free gas and "it's alive". Not sure how I managed to crud the gas up but I'm glad I thought to look more closely in the tank as there have been some other posts about the shutoff and a clogged screen. It also saves me from thinking the fuel pump had gone belly up as this tractor has really been a great runner ( in spite of it's owner ) and replacing the shutoff and screen will be an easy fix. Once again thanks for all the advice as I do appreciate it! Cod Share this post Link to post Share on other sites
