FH531V runs rough under load after 10 min

Discussion in 'Mechanic and Repair' started by byronlong, Jul 19, 2013.

  1. byronlong

    byronlong LawnSite Member
    Messages: 14

    Update on the coil replacement:

    I received the two coils I ordered today. Been over a week since I cut grass and we've had plenty of rain so it is thick and tall. I replaced one coil and set the air gap and put the covers back on. It took a while to crank since I drained all the fuel out of the carb when checking the bowl for crud. About 7pm now and mid 70's outside. I cut the back yard without any trouble. Mower was nice and warm now. Headed into the front yard and cut most of it and then it started. I would notice it when I would still be moving forward and then reverse the mower. Guess I need to replace the other coil.

    I pulled it into my garage and put the fan on it to cool it down. Took the other coil off and marked it as bad. I put the second new coil on and took off again. I have an extra lot that is approx 100 X 150 and it was pretty thick. I was powering through the grass with no problem. No skips or sputters. It was plowing through it and was still running smooth under heavy loads.

    I cut that whole lot wide open and on my last pass, yep, started sputtering again. I guess the cool temp had something to do with it running good for a longer period of time.

    So now I got two new coils and a mower that runs good for a little longer time period. I was pretty confident the coils were the issue. And they may be part of it. Still got something going on though.

    I'll be running it on the farm this weekend around my catfish ponds. Grass has really gotten tall there. I'll see how long it lasts in the middle of the day.
  2. Snyder's Lawn Inc

    Snyder's Lawn Inc LawnSite Platinum Member
    Messages: 4,530

    wouldn't have a bad head gasket on one side maybe both sides
  3. byronlong

    byronlong LawnSite Member
    Messages: 14

    Cut my in-laws yard yesterday. It was late, sun was down and temp was cooler again. Sputtered on me once. Even at wide open throttle, it doesn't feel like it is running wide open. Took it to the farm today and started cutting. Within 20 minutes, it started cutting out again. Mid afternoon, sunny and hot.

    Guess I won't be throwing either of those old coils away now after all.

    Would a head gasket act up only once it is hot?
  4. Valk

    Valk LawnSite Silver Member
    Messages: 2,720

    Wow. I realize you installed new coils, but have you/did you tried/try the 'pulling off one plug wire' idea to see if it makes a difference? Use a rubber glove or some insulated pliers if you do.

    IFF this is electrical, are you able/confident in using a multimeter? I'm not an 'electrical' guy...but a battery shop helped me to isolate an unusual issue that merely required a new ground cable from the engine block to the negative post. Not saying this is your solution, but I was beyond grateful they could figure out my issue (using a multimeter) at the time.

    Did you grow up in KS? I knew a B.L.
  5. byronlong

    byronlong LawnSite Member
    Messages: 14

    Nope, been in Alabama all my life.

    When the mower is just sitting there running wide open or idling, it doesn't act up so it's hard to diagnose.

    It has to be hot an under a load for it to sputter on me.

    I may just have to take it to the shop or go bonkers myself. I'm not much on electrical stuff other than just replacing parts.
  6. sjessen

    sjessen LawnSite Platinum Member
    Male, from Knoxville, Tn
    Messages: 4,379

    Do you think the engine is getting hot? If so, you might remove the shroud and check the cooling fins.
  7. byronlong

    byronlong LawnSite Member
    Messages: 14

    Well, it has to get hot before it starts acting up but I didn't notice any debris clogging any of the fins when I've been working on it. It's pretty clean and I blew any trash out with my air hose when I replaced the coils and checked the carb.

    May go ahead and start replacing fuel lines just to rule that out as a next step.
  8. byronlong

    byronlong LawnSite Member
    Messages: 14

    Took my yearly beach trip and forgot about my mower problems for a week but I jumped back on it the following day I returned.

    I replaced the fuel lines Monday night after work. Thank you Husqvarna for turning all the clamps toward the frame and making it such a difficult job to remove the old lines.

    Tried out the mower after work yesterday. It seemed to run at a higher RPM when at full throttle. It did sputter once when I first started but I thought it may have been a little air in the new lines being purged so I didn't think much about it.

    I cut my yard which was very thick after a week and a half. Started on my additional lot and was nearly finished and it acted up again. Not near as bad but it did sputter some as I would start forward motion or spinning the mower around at the end of a pass. Did this several times but not to the extent that I wasn't able to plow through the grass at a decent speed.

    No problems if it is just sitting there running wide open even with the blades engaged. Happens mostly when you start movement.

    I'm going to check the wiring under the seat and see if anything is loose or has worn insulation. Could be a worn wire shorting against the frame occasionally when moving.

    I do think the fuel line replacement has helped a great deal though.
  9. byronlong

    byronlong LawnSite Member
    Messages: 14

    Didn't notice any issues with wiring.

    Cut my grass a couple of days ago and the mower really started acting up again when it got hot. Outside conditions were upper 80's to low 90's but very humid. The time before it didn't act up much but the air temp was cooler as well.

    This time, just turning around at the end of a pass would cause the engine to bog down. It's like the sudden strain the hydraulics put on it gets it confused or something. I can pull the steering bars back to a neutral position and the engine with the blade engaged returns to normal operating speed. Then I slowly push into a forward motion and have to go slow for it to complete the pass without sputtering too much. I dropped the throttle some also.

    The only fuel line I haven't replaced is the formed one from the pump to the carb. I pulled it and blew through it with no sign of any obstruction. Turned the motor over while it was off and the pump seemed to be spitting out fuel fine.

    I'm about at the end of my rope on this problem. I've done just about everything that I feel comfortable doing so I will probably drop it off at the shop tomorrow.

    I do wonder about the safety switch in the seat though. I guess it would be worth a try to bypass that switch and see if it still acts up.
  10. Sharpcut 1

    Sharpcut 1 LawnSite Senior Member
    Messages: 452

    Put a Kohler fuel filter or a large automotive filter on there. You're getting vapor lock. Also, the O-rings in the carb were known to swell with the ethanol in the fuel. Kinda like the fuel line issue. Last summer was really hot here in Michigan, had the same problem with a bunch of Kawi's, went to the big filter, problem went away. All except one. His problem was the fuel solenoid magnet was getting weak and alowed the plunger to start creeping back into the jet. Slowly starving it for fuel.

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