B7800 no start issue

[Buck8one2]

This is my first post, and have read a bazillion threads regarding any issues I've had with my B7800. First I want to thank everyone for taking the time to respond to all the questions that seem simple but not so simple to solve. I've been searching the forum about everything concerning the "everything seems ok and cranks but does not start" issues. One issue I have not heard mentioned yet, is to pull the instrument panel look for mouse or rat nest. I found one and a lot of chewed wires which led to bare wires to the stop solenoid, start relay, and the controller. Not having time to replace wire I taped them up, no luck, same problem, replaced the stop solenoid, start relay, no luck same issue, time to replace the controller and the reason for this thread. Every drawing and parts list for the B7800HSD/mid PTO/and OPS (operator present switch) and they all list the controller as K3511-55222 so I buy one and get it, and it ain't right, plug connections are different. I pull the old one and have to skin the rubber covering back and it says 6C190-55512, so I google the number and yup that's the one. I contact the dealer and he finds the same thing, this number 6C190-55512 is not associated with the B7800 anywhere! Well I got the correct one ordered let you know how it turns out. The moral of this is before doing surgery on your tractor look for a rat nest first.

Buck

 

[RCW]

Buck - - - Welcome to OTT!

First, help me and others on OTT clarify your issue and actions, thus far:

1. It cranks, but no fire? Whether it cranks...i.e. turns over or not is a big deal.
2. You had a mouse nest in the dash....taped wires up?
3. You've replaced starter relay
4. You've replaced stop solenoid
5. You have an OPC, but it looks like wrong part

Second, I have a bunch of questions for you:

1. Does it smoke when it turns over? If so, what color is the smoke?
2. When was the last time it ran?
3. How old is the diesel fuel that's in it?
4. Are fuel filters are good, and are your getting fuel to the injection pump?
5. Are the air filter and intake manifold clean/clear (another nest)?
6. Do you have a multimeter or test light?
7. In Georgia, I'm assuming it's not below freezing...32F?

A diesel needs fuel, air and compression to run.

Most of my questions surround fuel and air.

Just trying to check fuel and air issues off the list first....always start with the simple stuff.....

If fuel and air are okay, certainly sounds like an electrical issue.....IF IT CRANKS, the electrical issue can stop the fuel from getting to the IP.

I'm FAR from the right guy for electrical troubleshooting. There are some sharp electrical guys here. I'm hoping they will have some good diagnostic advice.

Wish I could help further, but hopefully gets us a head start.

My questions are those the smart guys are likely to ask, along with some others they'll add.

Best wishes.

 

[Buck8one2]

Buck - - - Welcome to OTT!

First, help me and others on OTT clarify your issue and actions, thus far:

1. It cranks, but no fire? Whether it cranks...i.e. turns over or not is a big deal.
2. You had a mouse nest in the dash....taped wires up?
3. You've replaced starter relay
4. You've replaced stop solenoid
5. You have an OPC, but it looks like wrong part

Second, I have a bunch of questions for you:

1. Does it smoke when it turns over? If so, what color is the smoke?
2. When was the last time it ran?
3. How old is the diesel fuel that's in it?
4. Are fuel filters are good, and are your getting fuel to the injection pump?
5. Are the air filter and intake manifold clean/clear (another nest)?
6. Do you have a multimeter or test light?
7. In Georgia, I'm assuming it's not below freezing...32F?

A diesel needs fuel, air and compression to run.

Most of my questions surround fuel and air.

Just trying to check fuel and air issues off the list first....always start with the simple stuff.....

If fuel and air are okay, certainly sounds like an electrical issue.....IF IT CRANKS, the electrical issue can stop the fuel from getting to the IP.

I'm FAR from the right guy for electrical troubleshooting. There are some sharp electrical guys here. I'm hoping they will have some good diagnostic advice.

Wish I could help further, but hopefully gets us a head start.

My questions are those the smart guys are likely to ask, along with some others they'll add.

Best wishes.

Thanks for the reply RCW
To answer your questions:
1 no smoke no fuel
2 2 weeks
3 3weeks
4 yes
5 clear
6 yes
7 not in garage

I checked fuel and air to begin with then noticed no click from the stop solenoid checked for power at connector...none. Pulled dash and found nest and eaten wires under the nest and wires packed down and touching, figured shorted items and started replacing. While I had the stop solenoid off I stuck my finger inside and depressed the plunger inside smooth and free, but wasn't brave enough to turn it over with my finger in there or anything else for that matter. Tested solenoid directly to 12v and worked. Fuses all good as well.

 

[North Idaho Wolfman]

There is 2 different wiring harnesses for the B7800 depending on the serial Number, and yes there is a lot of parts on it that there are two different version of for it.

 

[Buck8one2]

There is 2 different wiring harnesses for the B7800 depending on the serial Number, and yes there is a lot of parts on it that there are two different version of for it.

Thanks Wolfman
That would explain it, but surely there would be schematics or information for it somewhere?

 

[Henro]

Thanks Wolfman
That would explain it, but surely there would be schematics or information for it somewhere?

I know close only is good in horse shoes, but the B7800 was supposed to be the economy version of the B2910 when it came out, and likely is very similar or identical in most respects.

here is the direct link to the WSM for the B2910 at Kubotabooks.com:

http://kubotabooks.com/AutoIndex/index.php?dir=Tractor%20Owners%20Manuals/&file=B2410_%20B2710_%20B2910_%20B7800_9Y011-13031%5B1%5D%20WSM.pdf

Kubotabooks listing says it is for the B7800 also...

 

[RCW]

You may have already seen this, but I went here, agreed to legal, then put in B7800:

Kubota Tractor Corporation - Illustrated Parts List (kubotausa.com)

I saw the S/N break Wolfman mentioned. Not a lot of other detail beyond the P/N for the two harnesses as 010 in the diagram, and their component parts.

 

[Buck8one2]

I know close only is good in horse shoes, but the B7800 was supposed to be the economy version of the B2910 when it came out, and likely is very similar or identical in most respects.

here is the direct link to the WSM for the B2910 at Kubotabooks.com:

http://kubotabooks.com/AutoIndex/index.php?dir=Tractor%20Owners%20Manuals/&file=B2410_%20B2710_%20B2910_%20B7800_9Y011-13031%5B1%5D%20WSM.pdf

Kubotabooks listing says it is for the B7800 also...

Thanks Henro
My WSM file listed as B2710 B2910 B7800, note it does not list the B2410. Without comparing page by page both are the same. The wiring diagram is identical and the picture diagram on the very last page shows the controller with the pigtail. which my controller has no pigtail. I do have another file which has exploded diagrams and parts listing for every part on the tractor and this is where I got the K3511-55222 part number. Apparently the dealers I have talked to are using the same file. I did find out that the part number 6C190-55522 is listed under the B2410-2910 and the B3030 series tractors but no not the B7800.
A bit strange but I have seen worse part number horror stories.

 

[Buck8one2]

Thanks RCW
Yes I have seen this one. If you look at drawing B10101 (switch mid pto type) and B10102 (switch mid pto type) on that same page it explodes the view and list part numbers. The diagram shows controllers with pigtails and the K3511 part number.

 

[RCW]

Buck - if it cranks, I think that rules the OPC itself out?

If the OPC itself were the issue it wouldn't allow it to crank...much like a seat, PTO, or pedal center safety switch?

Your issue may be more due to the chewed up wiring in the dash.

I've never fully understood how the OPC interacts with the safety switches.

I'm obviously guessing here., and don't want to send you on any wild goose chases... so take my advice with a grain of salt....I won't take any offense.

 

[Buck8one2]

GACK.....my apologies to all! I just went back and took another look at drawing B10102 and it does does list the correct 6C190 part number. Must have been seeing too much red and snorting fire at the time. I still wonder why dealers don't know of this. Its in the details I guess.
Thanks anyway guys, with your help the part number mystery has been solved.

 

[whitetiger]

I still wonder why dealers don't know of this.

What makes you think they don't? Did you order the part by the part number or by giving them the description, Model, and Serial number?

 

[Buck8one2]

What makes you think they don't? Did you order the part by the part number or by giving them the description, Model, and Serial number?

They gave me the number, they never asked about SN or age of the tractor. I gave them the model (B7800) with mid point pto and about the damaged wires to these 3 items and I wanted to order the stop solenoid, the start relay and controller. They came in and the solenoid and relay were correct but the controller was wrong. After a little help from the good folks on the forum I was informed of the different harness' and got with the dealer and we got the correct item ordered. The parts dept. did not list the 6c190 part as part of a B7800 but that part is listed for the B3030 and a few other models. Low and behold the part does show up on the second set of drawings if you know to look there but still does not come up under a B7800. In hind site I should have took more time and skinned back the rubber covering and looked for a part number in the first place. Anyway the mystery is solved, the correct part is on the way and I can return to incorrect one...I'm good.

 

[digger62]

• Had a similar problem with my uncles B7800, tried all the mentioned switches along with a fuel shutoff solenoid and ignition switch. Finally found that there is a controller located in the dash that regulates the fuel system that would periodically malfunction. It would start run then just quit, no pattern. the part number from Messicks is K3511-55222. About $130+. It is sealed so we could not tear it apart to see what failed. Been over a year with no issue.
  
  
  
  
  

 

[Buck8one2]

Well we finally got the B7800 running. Short story, rat eating insulation, rat builds nest on top of wires, nest packs bare wires down and shorts out relay, stop solenoid, and controller. Replaced all and still cranks but will not fire, yet all switches and lights work and still no click from stop solenoid. Pulled stop solenoid again and cleaned sealer and reinstalled with no sealer and tractor starts right up. The start solenoid grounds thru the body and sealer made for a poor ground.
Buck

 

[Henro]

Well we finally got the B7800 running. Short story, rat eating insulation, rat builds nest on top of wires, nest packs bare wires down and shorts out relay, stop solenoid, and controller. Replaced all and still cranks but will not fire, yet all switches and lights work and still no click from stop solenoid. Pulled stop solenoid again and cleaned sealer and reinstalled with no sealer and tractor starts right up. The start solenoid grounds thru the body and sealer made for a poor ground.
Buck

Glad to hear your success story! It is always great when the final resolution is reported.

 

[North Idaho Wolfman]

Well we finally got the B7800 running. Short story, rat eating insulation, rat builds nest on top of wires, nest packs bare wires down and shorts out relay, stop solenoid, and controller. Replaced all and still cranks but will not fire, yet all switches and lights work and still no click from stop solenoid. Pulled stop solenoid again and cleaned sealer and reinstalled with no sealer and tractor starts right up. The start solenoid grounds thru the body and sealer made for a poor ground.
Buck

Excellent to hear!

 

[RCW]

Buck - - - fantastic! Glad you got it....holy smokes, not a simple troubleshoot there!
Good for you!

 

[erniev]

Buck - - - fantastic! Glad you got it....holy smokes, not a simple troubleshoot there!
Good for you!

I have the same kind of issue; a couple of wires chewed on; motor cranks, won't run; whitish smoke when it cranks; 12 v at solenoid, 5.9 at relay ; can jump relay sometimes it starts; put in new relay from dealer, didn't help. Does anyone think its a bad relay or can they go bad if contacts get jumped and burn it out??
Thanks for any advice. (all new fuel , etc)

 

[Soloved]

I have a B- 7800 Kubota tracktor with almost 800 hrs. Does any one know if doing the 800 hour valve maintenance on it is very involved, or my have done it themselves? I want to try, but intermediated. Need support! It is a great tractor.