MX5100 won't start after bleeding

Jclayton · Jul 9, 2015

Hi everyone,
I just did some maintainance on my mx5100 that included cleaning the fuel filter. After reassembling the filter, I bled the fuel lines using the air valve as described in the manual. I let it run for about 30 seconds with the valve open. After that I shut it off and closed the air valve. I did a few other maintainance things like clean the air filter, etc. and when I tried to get it started again it quickly sputtered out and now won't turn over. I feel like I have some kind of air lock problem, but can't figure out why the air valve won't solve the problem. On this site, a video talks about a cylinder head decompression lever to help fire ups. Does anyone know if the mx5100 has one of these and where I can find it.

Any help is greatly appreciated.

Justin

Dr Honda · Jul 9, 2015

You probably have air in the pump, and in the high pressure lines.

So... bleed the pump again, and then crack the fittings at the injectors. Crank the engine (no glow) and make sure you push out any air in the lines. Once you have confirmed good fuel at the injectors, tighten the fittings, and I'm sure it will start.

85Hokie · Jul 9, 2015

Jclayton said:
Hi everyone,
I just did some maintainance on my mx5100 that included cleaning the fuel filter. After reassembling the filter, I bled the fuel lines using the air valve as described in the manual. I let it run for about 30 seconds with the valve open. After that I shut it off and closed the air valve. I did a few other maintainance things like clean the air filter, etc. and when I tried to get it started again it quickly sputtered out and now won't turn over. I feel like I have some kind of air lock problem, but can't figure out why the air valve won't solve the problem. On this site, a video talks about a cylinder head decompression lever to help fire ups. Does anyone know if the mx5100 has one of these and where I can find it.

Any help is greatly appreciated.

Justin

when you say it won't turn over......you mean it will not "fire" or run as apposed to not spin the engine?

I too think there is still air in the "line" - like Honda said - re bleed everything and do as he says....might take a bit of cranking to get that air out. Report back and tell us what happens.

Jclayton · Jul 9, 2015

Thanks guys,

It looks like I may need to go get some new tools. The injector fittings are so close together that I don't know what kind of wrench would fit between them. I think I read a 17 mil somewhere, but man are they tight.

Also, sorry, yes, I meant it will not fire. Just a little rumbling and then nothing.

Jclayton · Jul 9, 2015

Dr Honda said:
You probably have air in the pump, and in the high pressure lines.

So... bleed the pump again, and then crack the fittings at the injectors. Crank the engine (no glow) and make sure you push out any air in the lines. Once you have confirmed good fuel at the injectors, tighten the fittings, and I'm sure it will start.

Honda,
Should I leave the air valve (air cock?) open when doing this, or close it up to force the air to the injector fittings?

85Hokie · Jul 9, 2015

Jclayton said:
Honda,
Should I leave the air valve (air cock?) open when doing this, or close it up to force the air to the injector fittings?

close that fitting and allow the air to be pushed all the way past the injectors

Bulldog · Jul 9, 2015

When you say air valve (air cock) are you talking about a small round knob where the fuel line meets the injector pump?

North Idaho Wolfman · Jul 9, 2015

On newer tractors like the Mx5100 and when they have a Jet start valve on the side of the Injector pump you almost never need to open up the lines, the valve will do all the work at bleeding the air from a filter change.

Just open the valve and you should see the bowl fill full and it burps all out and back to the tank.

You can crank it with the valve open to push out any remaining air.
Close the valve and be on your way.

Jclayton · Jul 11, 2015

Thanks for all the help guys,

Opening up all four of the injectors wasn't an option because it was just too damn tight. What ended up doing the trick was removing the whole little round air valve knob (not just opening it, but removing the whole thing to really open it up) and a ton of air bubbles released that way. I suppose it would have worked just being open too, but I cranked on it like that for a while with no results and was afraid of killing my battery. Basically removing the whole valve sped up the process.

Thanks again everyone.

North Idaho Wolfman · Jul 11, 2015

Sometimes the smallest amount of junk or debris gets caught in the valve and that will foul up the works too, so taking it completely out was an excellent choice.

tonyg · Jun 18, 2018

Jclayton said:
Thanks for all the help guys,

What ended up doing the trick was removing the whole little round air valve knob (not just opening it, but removing the whole thing to really open it up) and a ton of air bubbles released that way.

Fantastic, thanks!

That solved my problem in record time, way more effective than turning the knob, and much easier than trying to turn the injector nuts.

I see (now) that Kubota recommends you not fully tighten the fuel filter, if you have had it off, until after you open the fuel cock. This eliminates the need to bleed in most cases...

whitetiger · Jun 18, 2018

Sounds like you were trying to loosen the injection lines at the top of the injection pump.
Never never loosen the tubes on the pump, always loosen them on top of the cylinder head at the fuel injector. If you turn the delivery valve that the line is screwed on to at the pump, you will change the fuel delivery rate and twist the line which changes the inner diameter of the line. You would then have to remove the pump, send it to a service center to be recalibrated and replace the twisted injection tubes.

I had a customer whos hired help did just that, every service center we contacted was 8 weeks wait. Customer needed the tractor and bought a $2300. pump to get it going.

lugbolt · Jun 19, 2018

whitetiger said:
Sounds like you were trying to loosen the injection lines at the top of the injection pump.
Never never loosen the tubes on the pump, always loosen them on top of the cylinder head at the fuel injector. If you turn the delivery valve that the line is screwed on to at the pump, you will change the fuel delivery rate and twist the line which changes the inner diameter of the line. You would then have to remove the pump, send it to a service center to be recalibrated and replace the twisted injection tubes.

I had a customer whos hired help did just that, every service center we contacted was 8 weeks wait. Customer needed the tractor and bought a $2300. pump to get it going.

Very good suggestion and thank you for putting this out there. Hope many read-and stick to it. Have had many in the shop for same issues.

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MX5100 won't start after bleeding

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