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doc724

The heat gremlin got my xi tractor yesterday

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doc724

From time to time, I have had this intermittent problem on my 520xi when I would shut if off, if it was hot, if would not restart.  It seems like a fuel problem because when I restart, it will catch, but there is no response to the throttle.  Yesterday I was using it with the FEL and after about 1 hr and 40 minutes (after I had moved about 9 yards of material), it just quit running.  Of course the bucket was full!  I let it sit and after about 2 hours of fuming and trying to restart with no success, I dumped the bucket, shoveled up the last remaining dirt into my trailer and hauled it to where I needed it.  Then I towed it into the garage with my old school but reliable C141.  Sure enough, 2 hours later, I turned the key and it started right up.  Anyone else xi machines seen this problem?  I am thinking it is the fuel bowl shutoff (dammed emission controls), but if it was energized, the only way it would lose power is if a relay failed.  I have yet to pull out the schematic (which of course it in tiny print that these old eyes can barely see!)

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RMCIII

Don, does it still turn over, just wont fire or does not do anything when you turn the ignition?

 

Rob

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gwest_ca

  I have yet to pull out the schematic (which of course it in tiny print that these old eyes can barely see!)

I think all the manuals are in the library here at RS in pdf format so you can blow them up as large as need be. Just open the manuals and use your model number in the search box to bring them up.

 

Tractor service manual and Kohler manuals are there.

 

Garry

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doc724

Rob, It fires right up if you let it cool for 4 hours.  Try to start it warm and it will turn over and catch but there is no throttle response to give it more gas.  That is why I think it is a fuel delivery problem.  I don't think it is a mechanical (ie fuel pump) problem as unless these is vapor lock, mechanical pumps are pretty robust.  Vapor lock is a possibility as the fuel pump and fuel lines run right on top of the valve cover and between the cylinder banks to get to the carb.  I am going to take Garry's suggestions and see if I can blow up the schematics so they are readable (and printable at magnification).  I am loathe to start replacing solenoids and relays due to the cost without doing significant trouble shooting first.

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userj8670

Vapor lock?

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RMCIII

Not 100% sure but that really sounds like a vapor lock issue.

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Forest Road

I had a similar problem on my Xi. I replaced the fuel line and added a filter. Then a new fuel pump. Fuel pump did the trick.

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doc724

Forest,

 

Did you put the same diaphragm pump as was there or did you go electric (or something else)?  Yesterday I used the tractor for almost 2 hours moving and leveling dirt.  In the last 15 minutes, I could hear the engine surging.  I drove back to the garage and dropped the bucket, shut off the PTO reduced engine speed to half throttle.  As soon as I reduced the engine speed, it died.  From you post it seems that the fuel line and filter had no (or not significant) effects. 

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Forest Road

That was a couple years ago. I changed out the fuel line and filter first. It's my standard "gonna keep this one" tune up protocol. Still had the same problem.

From what I recall it would run perfect for 15 min to an hour. Then abruptly shut down. Purchased the same vacuum fuel pump. Haven't had a problem since.

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doc724

Today's update:  I ran the machine for only one hour yesterday, but I could hear it "hunting" a lot of the time.  Finished the work and put it away for the day.  This morning it would not start, but it would turn over and catch and them maybe run like it was running out of gas-again no response to throttle.  So I did a little diagnostic work.  I confirmed that all the relays work and that the fuel shutoff solenoid responds to voltage (I can hear it click).  What I cannot confirm is if the solenoid pulls the shutoff back enough to let the engine run.  You have to pull the carb to do this and I was just not in the mood.  I confirmed that there is 12V to the fuel solenoid when the ignition is in the run position. 

 

That left me with replacing the fuel pump.  Kohler pump was over $60 locally, but a Briggs pump which was identical to the one that was on there was $22 so I went with the low cost option.  With the new fuel pump installed, I tried starting and it would catch but not run.  After a few more tries, it backfired so I am guessing there is too much gas at the moment in the  cylinders.  I have not yet checked spark, but the fact that it run (but just does not respond to throttle would lead me to believe that this is not the problem).  I checked to see where the ignition module is located - drats, it is on the left side right up against the frame rail.  You would have to pull (or at least unbolt and lift) the engine to get access. 

 

So it is sitting in the garage for now.  I think on it tonight and try again tomorrow.

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doc724

Tuesday update:

 

After a few simple electrical diagnostics, the neighbor convinced me to squirt about 1.5 cc directly into the cylinder, reinstall the spark plug and then fire it up.  Sure enough, after a few extended cranking cycles, it fired and ran.  I let it run for 5 minutes, went inside to have lunch, came back to restart it and it would crank and fire/cough but again would not respond to the throttle.

I let it sit for a day and on saturday, I turned the key, it fired up and I ran it for two hours.  Just as I was taking off the chains and was preparing to move it to its parking space to remove the FEL, it dies.  I pushed it back into the garage and let it sit.

Sunday, on my 50 mile bike ride, I thought about the problem some more.  I am convinced it is a fuel starvation problem (not vapor lock), but I am suspecting that the root cause is electrical.

I think the fuel shutoff solenoid is losing 12v supply when it gets hot.  There are three electrical "parts" in the circuit;  the ignition switch, a diode, a relay (start relay but only in the start mode) and then finally the fuel solenoid.  In the run position, the ignition switch (different terminal) and a different diode connect to the solenoid.  I have yet to find the diodes and there may be two diodes in one package.  I know that semiconductors do not like heat and this winter, I could smell something "burning" after I shut down from snowblowing, but in the frigid temps, I was not about to investigate.

Yesterday, if fired right up and I removed the FEL.

What do you think?  Am I on the right track or out to lunch?  Any experience you all can share would be welcome.
 

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Forest Road

Motorcycle or bicycle ride?

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doc724

bicycle!

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Forest Road

Good man! 3 kids 9 months to 6 years just haven't had anytime this year.

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doc724

I used to bicycle 10K miles per year, but I crashed last year and broke my hip.  It became necrotic and I had to have a full hip replacement in March this year.  Things have been slow and I only have 1000 miles in 2014

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