john deere 316 w/ onan p218g engine

Hello new to the site,have spent the last 2 weeks on line,this onan has me pulling what hair I have left out!surging problems,backfiring,and dies when put in gear,have check vales,rebuilt crab twice!sealed intake manifold,replaced coil.all gas lines and fuel pump,dont no wear to go next,thanks for all help, Love this site!

First thing try to isolate problem to ign/electrical system,fuel system or possible mech/internal wear problems in eng.

Ign system-if you haven't done so already install 2 new plugs,after that check plug leads with an ohmmeter some P series eng had carbon core leads & these leads can/do go bad,if leads check good with meter install an inline spark tester in each plug lead & run eng 3-5 min(if eng has an oil pressure sw/float sw disconnect same before starting eng)to confirm eng not running on 1 cyl sometimes,after that try to drive tractor while watching spark tester's,if you lose spark when trying to move tractor then problem probably in safety sw's,ign sw or wiring on tractor,if this is the case remove wire from + terminal on ign coil & run a jumper from coil + terminal to + terminal on battery,start eng & try to move/drive tractor,if you can there is nothing wrong with ign system.Reconnect oil pressure sw/float sw,if eng dies then problem in lube system.

fuel system-the most common cause of eng surging/hunting for it's speed,backfiring & dieing is usually caused by plugged,dirty or restricted idle passages in carb body in addition to possible misadjustment of needle valves OR an air leak in intake manifold,most common cause of air leak is gasket bad between manifold half's & loose/broken rivets even if you sealed joint around outside it still may be sucking air around gasket or loose/broken rivets,take a can of spray carb cleaner with ext tube & with eng running at idle slowly spray joint all the way around manifold,if eng speed changes while doing this then gasket bad/leaking or rivets loose/broken,if this is the case then either replace manifold or drill out rivets,remove gasket & clean joint & pack with red rtv sealer & reassemble manifold with screws,lockwashers & nuts.

internal mech problems-excessive cyl/ring wear causeing low compression,leaking/bad head gasket(s)worn valve guides causeing fuel mixture to go lean due to sucking air around valve stems.

new plugs,coil/wires off running 17hp,manifold apart and sealed with Honda bound new rivets,new head gaskets,valve guides fill good,eng only has 430hr on it,oil sw disconnected, jumper from coil + terminal to + terminal on battery,try to put in gear it dies,runs good jest setting,air / fuel screw has no affect,good spark,will set and idle,do you know of a diagram of the idle passages in crab? been in it twice,one rebuild kit,and a Ultrasound bath,check valve lash tomorrow, don't no what I'm missing, Thank You