416H Shuts down when hot

[Furious 23]

I have a 416H that’s not running properly.  It will run for 10-15 min at high RPM then sputter and die.  Will start back up and run at idle only.  As soon as I give it any throttle at all, it chokes and dies.  Let it sit for 30 min and will do the same thing after running fine for 10 min.  I got my hands on a spare ignition trigger so I replaced it and fixed some of the wires in the 9-pin connector that were looking burned.  Took them out of the connector and wired them separately.  While it was apart, I decarbed the heads and adjusted the valve clearances.  So, new ignition trigger, freshly decarbed heads, fixed some (not all wiring), new spark plugs, gas cap is good.  Any ideas?  Coil?  What am I missing?  I love Wheelhorse tractors, but I’m regretting buying this one with the Onan.

[ri702bill 8,345]

Coil?? Probably not. IF the coil went to open circuit, it would not "close" to give spark until it was cold. Had a Kohler K-161 like that. Do you have an inline spark checker?? Tells you if there is a spark or not to rule that out.

[oliver2-44 9,761]

Have you cleaned the fuel system

Replaced hoses.

Cleaned carb.

Cleaned tank - most fuel shut off valves have a screen inside the tank.  Trash can get sucked on to screen as you drive and partly plug it.  Then after the tractor sits awhile the trash drifts off and it seems to run fine.  

Next time you run it and it stops , then will only idle, take a squirt bottle and squirt gas in carb.  if it revs up you have some type of fuel problem.

[Furious 23]

Don’t have an inline spark tester.  I’ll have to see if I can get one.  Fuel lines are new, fuel tank is clean.  I’ve watched the fuel filter when it starts to die and it is never less than 3/4 full so I don’t think it’s a fuel delivery problem.  What else can it be?  When i decarbed the heads, there were no apparent loose valve seats.  Could one of them be coming loose when it’s hot?  If so, what would be the indications?  I’ve done a compression check and both cylinders are good.  #1 is 102 and #2 is 100.

[lynnmor 7,308]

I hope you cleaned out the carburetor while you had it off.  A bad coil can be a problem so a spark tester might help you, Harbor Freight has them.  An Onan can run rather well with loose valve seats and only if they are very bad will that problem be noticed.  Yes, seats loosen with heat.  The amount of fuel in the fuel filter will tell you exactly nothing.  The idea, mentioned above, of squirting some gas in the carburetor can help diagnose the problem.  Just remember, on this forum Onan is the cause of the problem, dirt, fuel supply, bad wiring, etc. shouldn't be an issue, only Onan.

[rmaynard 15,514]

I will go out on a limb and say that you may have a gas cap venting problem. Loosen the cap so air can be pulled in. I have had this happen and the fuel filter still shows gas in it. With a clogged or partially clogged vent you are creating a vacuum which is preventing fuel from moving, so it will appear in the filter, but it's not moving. Letting the tractor sit allows air to slowly return to the tank. 

[Furious 23]

@lynnmor, I couldn’t agree more. I hate this Onan engine. Really regret buying this tractor but the wife and kids wanted a hydro. I should have gone with my initial plan and bought a 314-8 with a kohler.  I’ll tinker with it some more this afternoon and provide an update. Note, I’ve had the same problem with the gas cap on, loose, and completely off, so it’s not a venting issue. 

[peter lena 8,634]

@Furious   somethin I regularly do , on a  pick up is to run it in , see how it sounds , responds , on a SEPARATE GALLON OF  HEAVILY TREATED FRESH FUEL , that way you are completely separating from existing set up . also refer to fuel line breakdown / debris , might also have a wire chafing issue . fixed wiring , held in place , without  protection , often shows itself   , with a similar problem . might even go after related ground points , break free, wire brush , dielectric spray , pete  

[rmaynard 15,514]

My 1996 416-H has 1678 hours on it. Original P-216 Onan engine. Never been rebuilt. The only thing I have done is regular maintenance and I put new spark plugs, and wires in when I got it. The engine ran great until it started to surge. I solved that temporarily by spraying carb cleaner down the throat. Permanent fix was with an aftermarket carburetor. I replaced the fuel pump only because I broke it while adding a check valve. Here's what I personally have found about the P-216.

Ignition modules either work or they don't.

Ignition coils work or they don't. They don't get overheated because they are cooled by the passage of air around them while the engine is running.

Valve seats, which notoriously have problems in the P-220's don't seem to have problems in the P-216's unless the engine cooling airflow is completely blocked.

My 2 cents worth says to address the carburetor.