19.5 HP won't stay runnning

backwoods bum · Dec 27, 2016

19.5 HP (John Deere LA110)
Engine model 31P677 0130 E1

Turns over several times (15-20x) before engine finally starts. Once it starts, will stay running on full choke for a few seconds before cutting out. Moving throttle out of choke and between idle and full open does not help. The cutoff seems like it is starved for fuel, since leaving the choke on does not cause the typical shaking and thick exhaust.

Have done the following:
- new fuel pump and filter (filter is full)
- compressed air through fuel line from tank to eliminate any debris
- cleaned fuel line to carb
- cleaned vacuum line to fuel pump
- installed new carb (fuel solenoid clicks on key turn)
- installed new head gasket
- checked valves/push rods/rocker arms

Any other ideas on why this engine will not stay on? Thanks in advance.

bertsmobile1 · Dec 27, 2016

Get a can of starter fluid & an inline spark tester the ones with a red neon tube work best.
Remove the air filter & give the engne a LITTLE squirt of fluid.
If it starts, keep giving it short squirts of starter fluid.
If you can keep it running for better then 30 s to a minute you have a fuel delivery problem.
Watch the spart tester while you are doing this.
If you get a strong orange flash all the time then the ignition is good but if it cuts out before the engine stops spinning your problem is in the ignition or safety circuits.

backwoods bum · May 9, 2017

Update: Did the steps above, had good spark and would run with starting fluid.
Replaced the fuel line from the tank to the filter in case there were any small holes or cracks in the line.

Now engine will stay running but surges constantly, like an engine does when you run it dry. It does this no matter what the throttle setting, it just surges to a higher RPM when the throttle is open. I pulled the fuel line from the carb and it is pumping gas. The carb bowl has gas when it is removed from the engine.

Could the seat safety switch be an issue? Governor need adjusting? Other ideas?

There's a gremlin in this thing somewhere that I just can't seem to catch.

Help!

cpurvis · May 9, 2017

You say you installed a new carburetor.

Did you set the main jet to whatever preliminary setting it's supposed to have, like 1 1/2 to 2 turns?

It sounds to me like that jet needs adjusting.

backwoods bum · May 9, 2017

Thanks for the feedback.

I set the needle at 1.5 turns out from seated, then went 1/4 turn increments in both directions - waiting about a minute between turns to let the engine respond.

Did not make a difference, other than almost cutting out when the valve was fully seated.

cpurvis · May 9, 2017

It will (or should) respond much quicker than a minute. That's controlling the fuel that's going into the engine right now.

That jet must be partially clogged. You wouldn't think you'd have to check things like that on a new carburetor. Also, does this engine have the fuel cut-off solenoid on the bottom of the float bowl? If so, maybe it isn't opening all the way. Or maybe you have an air leak. Bad gasket, maybe?

bertsmobile1 · May 9, 2017

As you have correctly noted, surging is always caused by insufficient fuel so good chance your new carb either has the float level too low or the main jet is too small.

backwoods bum · May 10, 2017

Thanks all - I'll pull the carb and clean/check it again.

backwoods bum · Jun 9, 2017

Update - Finally got it running smoothly again.

Thanks for the heads up regarding the new parts/jet possibly being too small. Compared the original and new jets and the new jet was noticeably smaller.
Put the old carb assembly back on and it fired up and ran perfectly.

Looking back, I think I had a combination of issues with a cracked fuel hose from the tank + a carb that needed serious cleaning.

Glad this is finally done - thanks again!

19.5 HP won't stay runnning

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