4720 hard start

SwLWildcat · Jun 8, 2014

I have a 2012 4720. Up until now it has always started good in the warm weather. When it's below -15 it has to be plugged in to start. Yesterday it fired right up and I used it for about 3 hours with the chipper on the 3 point hitch. We managed to plug the chipper up and as we had other things to do last night I just parked the tractor for the night with plans to unplug it today. This morning I went to fire it up and it just cranked. I checked all the oil levels among other things and the only thing I can see is the engine is half an inch overfull on the dipstick. Coolant is normal so I immediately thought the transfer pump is leaking internally. If that is the case it should fire up with a shot of starting fluid I thought. Sure enough it fired right up and runs fine. I pulled the FEL off anticipating having to work on the engine. When I shut the tractor off to disconnect the 6 quick attach couplers it cranked over about 6 times before it caught, but it did fire up on its own. Anyone else have this issue? It being the transfer pump would make sense to me as it would leak diesel into the oil when running, and when not running air would get back in the lines causing a hard start. Anything else it could be? Tractor has about 200 hours total time.

Thanks.

patchnball · Jun 9, 2014

take it to dealer...should still be under warranty

sunnyside360 · Jun 9, 2014

It could be a fuel/air leak problem as you suggest. However, a weak battery that doesn't turn the engine over fast enough will act in a very similar way. You can prove/disapprove possibility of a weak battery by putting a jump pack on the battery and try starting the engine. If it starts right up with the jump pack, a battery cell is going bad or there is a problem with alternator or voltage regulator.

SwLWildcat · Jun 11, 2014

patchnball said:
take it to dealer...should still be under warranty

Unfortunately the Warranty ran out a month ago.

I ordered a new lift pump and it arrived this morning. I'll install it tonight if I get a chance. I thought it would cost more than $125.

9973720wb19 · Jun 11, 2014

once my 4720 have a very hard time starting in the cold - left it outside so it'd be close by for the morning. anyway, it seemed to me that while using it the day before, the melted snow and ice ran over some fuel lines and other lines and overnight they froze the lines. after taping on the lines with a rubber hammer - pre heating - turning the throttle up - i just let the thing crank did not let up on the key - then all this black smoke started to come out and it fired up. make sure you have a fully charged battery.

SwLWildcat · Jun 16, 2014

The problem was the lift pump. Remember that 9mm wrench that is in every wrench set you buy that you thought was useless as you have never seen a 9mm bolt? Well I found out the lift pump is held in with 2 9mm head bolts.

The other neat thing is my bolts were super tight so the open end would just spread (cheap wrench). I had to grind down the box end due to clearance issues.

JD5210 · Jun 16, 2014

I would interested to know how you determined it was the lift pump?

sunnyside360 · Jun 16, 2014

JD5210 said:
I would interested to know how you determined it was the lift pump?

Yes, me too for future reference. Good you got it fixed. I don't ever recall any of these pumps having to be replaced on 4X20 engines and with only 200 hrs on the meter, must have been marginally defective since new.

SwLWildcat · Jun 16, 2014

JD5210 said:
I would interested to know how you determined it was the lift pump?

The tractor normally starts right away and I have never had it crank for more than a second and not start when the temperatures are above freezing so I knew something was not right. I always check the simple stuff first. Nothing easier to check then all the oil levels. I noticed the engine oil was well over where it normally should be, by about half an inch. For the engine oil to go up something has to be leaking into the engine oil and it can only be the following.

1) Hydraulic/transmission oil.
2) Coolant
3) Fuel

The first 2 were eliminated by checking their respective levels, and both found to be where they should be, which just left diesel.

I could have sent out a sample for analysis, and I still may.

Once I was sure it was diesel in the oil there are only a few ways it can get in there. If something in the head had failed and dumped diesel into the oil I don't think the tractor would run normally when it did fire up on starting fluid. Seeing as how it did fire up on starting fluid and then stayed running on it's own confirmed my suspicion that it was starving for fuel and air had entered into the system somehow and the fuel in the line drained back to tank and had to be primed. If air had gotten into the system after the injection pump then the check valves in the system wouldn't have let the fuel drain back to tank, so the air had to be getting into the system between the tank and the injection pump. The leak also had to be higher then the level of fuel in the tank and lines, or I would have an external leak on the ground. Combined with the high oil level in the engine led me to confidently believe it was the lift pump. When I pulled the lift pump out of the engine there was some diesel on the plunger that is actuated by the camshaft, as well the camshaft was clean and free of oil on the lift pump lobe. I stuck my finger in the hole where the lift pump mounts and felt the bottom of the lobe on the camshaft and when I pulled my finger out it had a drop of diesel on it. Once the pump was replaced and the system bled the tractor fired up normally, and has fired up normally a dozen times since with about 8 more hours on the meter. The engine oil is not going up anymore so I am confident that I have the problem fixed. I dumped the oil and put new oil in it, I thought I had another oil filters but couldn't find it so I left the old one on. I got a new filter today and will change the oil again this week as well as the filter.

I got a new MX6 mower on Saturday so I was anxious to give it a try. That thing is a beast! I was mowing down trees 10 - 20' tall and up to 4" in diameter.