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Discussion Starter · #1 ·
Well the title pretty much explains my problem... filled one of our 6420's completely full last night before I left work. When I started it back up, fuel gauge showed 1/4 tank. I figured the fuel sending unit bit the dust as we had it replaced last year after it kept giving faulty readings and finally threw a code.

Today I went to bush hog one of our fields...ran back to the barn for a break after about an hour or so. Gauge showed empty. Went to start it back up and it wouldn't start...just cranked like it was out of gas. Checked the tank just to be sure, still nearly full. Emptied the water separator in the fuel line and it filled back up with diesel like normal.Tried to crank it again and still nothing. Finally gave in and shot a little ether into the intake. It fired right up, but once it burned the ether up, it died just like it ran out of gas. It wasn't sputtering before I shut it down or anything. So now the tractor is stuck in front of our barn unable to be moved because we can't get it to start (I also put another 5 gallons into the full tank "just in case").

Any ideas why it would run out of gas and show the tank is empty when it's almost completely full?

Thanks in advance for any advice you may be able to offer!
 

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Discussion Starter · #3 ·
I think that might be what it is...I was messing with it some today and I pulled the bottom drain plug out of the final water separator and when I kicked the engine on (and when I cranked it over), I got no fuel refilling it whatsoever. Sounds like I just gotta wait on the service tech to come out though...I'm a basic auto mechanic, but I don't know squat about diesel engines. Argh...just wish I had a way to move the tractor out of the way...
 

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The fuel sending unit also has the electric fuel pump incorporated into it. Saounds like either some wiring lost contact or the sending unit/pump assy. bit the dust. Also could be a blown fuse. Did you check the fuse panel?
 

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Discussion Starter · #5 ·
The fuel sending unit also has the electric fuel pump incorporated into it. Saounds like either some wiring lost contact or the sending unit/pump assy. bit the dust. Also could be a blown fuse. Did you check the fuse panel?
Never even considered the possibility of a blown fuse...although the fuel gauge had been messing up for a day before its refusal to start so I'm not sure if the fuse would be the only issue. The JD service tech will be out first thing in the morning and I'm gonna be kicking myself if it is just a blown fuse.

I'll post an update on here when the problem is solved just for future reference.
 

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Discussion Starter · #7 ·
Update:
Blown fuse:banghead3

...but on the bittersweet side, the fuel sending unit is definitely bad and the electric fuel pump may be bad as well.

We got it running after replacing the fuse...but the gas gauge was still showing empty. I took it out in the field and started to use it and as soon as I got to the far side of the field, it died and I got to take a nice walk.

I swapped out the fuse and it popped as soon as I cranked the engine over...tried again, same deal.

Later I went out and put more diesel in (approx 2-3 gals until the fuel level reached the top of the filler neck). Replaced the fuse once more and it started so I drove it like a bat out of **** back to the barn and parked it. I think the fuel sending unit is shorting out when the float reaches a certain point just a hair under full and is blowing the fuse...but the service tech thinks it also could be the pump because we just had the sending unit replaced last year for being erratic.
 

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Discussion Starter · #8 ·
'nother update... service tech was out and fixed it. It ended up being a two part problem. The fuel sending unit was bad because the float had filled up with diesel...hence why it showed empty even on an empty tank, but it was not shorting out. The electric fuel pump was also bad...it was blowing fuses because the pump would get hot after running for a bit.
 

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Discussion Starter · #10 ·
Makes you wonder how the old tractors ever ran without all the electronic JUNK dosen't it?

Ronnie
Yeah, no kidding! We've got another identical 6420 that's been a nightmare for the service techs for over a year now...if you clutch it while its rolling and start to let the clutch out before its come to a complete stop, it'll jerk real hard like you just dumped the clutch and then it'll clutch like normal after you've nearly crapped yourself. The codes say there's a short in the clutch proportioning valve circuit or something like that. He's changed that valve twice...adjusted the potentiometer on the clutch...replaced the potentiometer on the clutch...can't find a shorted wire anywhere...problem still exists. We were sure we had it fixed yesterday...he noticed fluid in the connector that plugs into that valve so he replaced it again thinking the fluid was pushing up through a crack in the senor when it got warm (it only acts up after about an hour of use) and causing the wires in the harness to short together. I don't even want to see the bill when they get that one figured out...lol...my boss is gonna have a heart attack!

The worst part...these tractors both have right at about 300 hrs on them...they have been babied compared to how hard some of you folks probably run your tractors when you're working in the fields from March-November or however long the planting/growing/harvesting season is.
 

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Discussion Starter · #12 ·
Yet another update...I'm full of those lately, huh?

Took the tractor out to bush hog a field yesterday...ran it for about 20-30 minutes and BLAM...died. Fuse blown, wouldn't restart. Replaced fuse, blew it as soon as I kicked the ignition on.

Blown fuse is 4th row, 11th down I believe...10amp fuel pump fuse.

As I mentioned above, both the pump and fuel sending unit were replaced.

Here's where it gets interesting...I went out there today, popped in a new fuse. Started right up. So I ran it back to the barn as quickly as I could.

I learned yesterday that it's too heavy to lift the front wheels off the ground with our backhoe (since it's kinda hard to steer having hydraulic steering and an engine that won't run). I did tow it about 15 feet forward so I could swap the bush hog onto another tractor.

Anyway... today I decided to run it and take notes on how long it would run until it stalled and blew the fuse...gauge readings, codes thrown, etc.

Here's the notes I took:
-Started engine at 4:46pm
-Entered diagnostic mode and cleared all codes so i could get only the codes relating to the engine stalling
-Ran with all accessories off until 5:16pm at a constant 2000-2010 rpm
-At 5:16pm I kicked on the cd player so I could resolve my boredom issues and cranked the rpm's up to 2150. I also kicked the PTO on with no load for about 3 minutes or so but didn't see any immediate issues so I shut it off to reduce the variables when it stalled.
-At approx. 5:20pm I once again raised the rpm's to 2200
-Engine stalled and fuel pump fuse blew at 5:26pm

All gauges were within normal specs at time of stall and there were no warnings flashing or sounding at the time.

Once it completely died, it began to flash lights at me...red and blue I think...if not all three. Was so hot/bored at that point I forgot I was supposed to be taking thorough notes...lol

Entered diagnostic mode and pulled the codes thrown when the engine stalled.

They were:

EPC 306060.31
ECU or BCU is/are not sending any data (engine speed)

SFA 324053.31
Engine speed too low (during operation)

Thoughts?

And I was mistaken on the hours...the tractor mentioned above with the transmission problems I believe has 299.x hours. This one has 477.x hours on it. Both are same year...identical make/model with same features except one has a cd player and the other has just a radio. Other than that...identical. Unfortunately, due to their age (can't remember what year they are...early 2000's I think), they are out of warranty.
 

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In an earlier post, you mentioned the "boss" sooner or later, surely they;re going to be tired of spending on a machine that isn't producing anything but trouble & with the low hours, i'd be awful tempted to sell them.
With little to do this morning, i went to this site http://www.ssbtractor.com/wwwboard/messages6/

Seems like all the newer models have electrical problems.



Ronnie
 

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Discussion Starter · #14 ·
In an earlier post, you mentioned the "boss" sooner or later, surely they;re going to be tired of spending on a machine that isn't producing anything but trouble & with the low hours, i'd be awful tempted to sell them.
With little to do this morning, i went to this site http://www.ssbtractor.com/wwwboard/messages6/

Seems like all the newer models have electrical problems.



Ronnie
Ouch... yeah, I scrolled through there...lots of issues. I don't wanna sound like I'm bragging or anything, but my boss is a multi-millionaire (owned a large car dealership for many many years amongst a lot of other things)..so while these repairs are surely going to leave him pretty ticked off, they aren't going to do much harm to his bank account. But he's already clarified with me...I do not pay a single bill until both tractors are confirmed fixed. So the company servicing them will be the ones forced to make this right. I just wonder if they're going to get John Deere involved eventually since they've been throwing parts at it for the past year with no luck (it's beginning to look like both problems are related to electrical gremlins). I know my boss is going to refuse to pay for all the unnecessary parts so they're going to end up eating a lot of the costs.

On that note...with our other problem, the service tech said he's stumped and will be opening a dtac case (or something like that with JD)...anyone know exactly what that is? I didn't think to ask...just assumed he was going to ask them if they've seen the problem before and find out how they fixed it.
 

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DTAC stands for Dealer Technical Assistance Center. It is a website that dealers can access to look for any known problems, and they can contact deere and company troubleshooters/engineers to help with problems.
For your problem, I'm not sure which fuel system you have. There are three or four possibilities for a 6420 depending on serial number and equipment. I suspect you have a bad temperature sensor if you have a rotary style injection pump. I have seen these short out when the engine reaches a certain temperature. They always work fine on cold start. It is a sensor in the thermostat housing with wiring that leads to the injection pump. Try disconnecting the wire at the sensor and running it. The engine will run while disconnected. The sensor controls cold start advance on the pump. In cold weather the engine will smoke more while unhooked.
 

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Discussion Starter · #16 ·
DTAC stands for Dealer Technical Assistance Center. It is a website that dealers can access to look for any known problems, and they can contact deere and company troubleshooters/engineers to help with problems.
For your problem, I'm not sure which fuel system you have. There are three or four possibilities for a 6420 depending on serial number and equipment. I suspect you have a bad temperature sensor if you have a rotary style injection pump. I have seen these short out when the engine reaches a certain temperature. They always work fine on cold start. It is a sensor in the thermostat housing with wiring that leads to the injection pump. Try disconnecting the wire at the sensor and running it. The engine will run while disconnected. The sensor controls cold start advance on the pump. In cold weather the engine will smoke more while unhooked.
Thanks, I'll check tomorrow if I have that setup and if I do, I'll disconnect it and run it and see what happens.
 

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Discussion Starter · #17 ·
I saw there were 2 sensors in the thermostat housing...one had 2 wires running to the injector pump, the other had one running to it I believe. I unplugged the top one with the 2 wires running to it...orange and red.

Engine ran for over an hour at varying RPMs without ever popping the fuse and dying...so either I didn't run it long enough this time around or that sensor is indeed to blame. Thanks a lot for the suggestion!
 
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