John deere F620 dies whe pto is turned on.

Mastercraft

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HI all, new here I have a question. I have been working on a John deere F620 and it loses power and shuts off. It also just doesn't seem to have the power it use to have. When you trun the pto on it takes about 10 seconds or so then it shuts off when you try to drive it. If you trun it on and let it set in one spot it when run but its like it has no power. You can also drive it around all day with the pto off, but it still seems to have a lack of power.

My first thought was it must be a safety switch I tested all of then and they where good.

I put my tachometer on the tractor and it was running 6000RPM at wot. I did a compression test on one of the cylinders and it was 110psi a little lower then I would like it to be but I can live with it. The gas tank is in the way so I didn't do the other cylinder.

I went to do a fuel pressure test and of course my gauge decided not to work so I put a fuel pump on it any way it was only $20. It acted like it was runing out of fuel when it shut off so I thought that a fuel pump might work.

My battery is dead so I haven't tryed it after I put the fuel pump on.

All the pulleys on the mower spun freely too.

it has blue spark on both cylinders.

I'm just chasing my tail on this one any one have any Ideas.
 

Rivets

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Had a similar problem on a unit two weeks ago. Turned out to be a bad coil on one side. Two ways to diagnose to see if yours is the same. One way, is while the engine is running remove one of the spark plug wires and notice a change in engine speed. If it drops that side is good check other side. Do this with a good insulated pliers or it will wake you up quickly. If you see no reduction in speed, you may have an external spark, but that cylinder is not firing. The second way to test is remove a plug wire and see if the engine will start. It won’t start with the bad coil wire off. If you do find a bad coil, replace both while you have the unit apart.
 

bertsmobile1

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And check the settings on your tach.
No way that engine will do 6000,,,, for very long.
3000 is probably what it is doing but if you trust those numbers to set the low idle the engine will be running way too fast.
 

Mastercraft

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Well I thought I had good blue spart on both coils, but I didn't. Yeah the tech was in the wrong setting 6000rpm that is way to high on that engine. I must have been working on boats to much lately. I found out why I have been having such a hard time with this tractor the mice got into it and eat a coil wire and who knows what else.
 
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