M7040 no start but weak attempt

[dstig1]

I'd still go with a bad connection. You may have continuity, but it could still be high resistance for example, thus killing your current flow. I would disassemble all ground contacts, clean and reassemble, and look at wiring for anything looking odd. Plus all battery and starter cables.

You have my sympathies as tracing electrical stuff like this can take a ton of time and is very frustrating.

 

[RoyKing]

do a voltage check working back from the battery, RELAYS can burn and deliver a low current flow, you will see it as a voltage drop with the load on. So if batt side of relay shows 13.2 and load side shows 12.2 bad relay.

 

[gwdixon]

Just because the battery shows a full charge doesn't mean it's so. I just went through this the other day, I put my charger on the battery, waited about 2 hrs and nothing, still showed fully charged. Couldn't get a load test at the dealer, their machine said re charge and tray again...lol
I installed a new battery and both new cables along with cleaning up (wire wheel) all connection points, she starts like a new tractor now. Good luck.
ETA: what is the voltage at the battery? Mine only showed 11.8 volts.

I'd still go with a bad connection. You may have continuity, but it could still be high resistance for example, thus killing your current flow. I would disassemble all ground contacts, clean and reassemble, and look at wiring for anything looking odd. Plus all battery and starter cables.

You have my sympathies as tracing electrical stuff like this can take a ton of time and is very frustrating.

Thank you for the advice. The battery is brand new - manufactured 12/18. It was taken into the shop, water added, and put on a charger before installing. It showed 12.6V. Immediately on installing the tractor was tried and exactly the same symptoms happened. So I ruled out the battery as the source of the problem. It still shows 12.6V after all of my fooling around with the cables.

The ground cable was totally bypassed with a jumper cable. Took off the tractor's ground cable and attached a jumper to the battery negative and an engine bolt. Tomorrow I'll try the same with the positive post to the starter solenoid.

 

[gwdixon]

do a voltage check working back from the battery, RELAYS can burn and deliver a low current flow, you will see it as a voltage drop with the load on. So if batt side of relay shows 13.2 and load side shows 12.2 bad relay.

Started that process today but the relays are behind the dash - which is turning into a pain to get off. Apparently, there is a 10MM bolt between the hood hinges that is holding in the top of the dash. A real bugger to get to.

Oh, well. At least the tractor is in a barn. We are getting hammered with rain and wind here in Northern California this week. Can't take the tractor onto plowed ground anyway this time of year. I do use it to haul firewood to the house. Now the backhoe will get that task.

A big thanks to all who have contributed (and are sympathetic) so far. I have a path and a destination. Now to get there.

 

[sixdogs]

A fellow I know is an electric trouble shooting tech at a street rod wiring company and we met when I had a strange wiring problem that defied diagnosis. In a way, it behaved like yours. The guy told me up front that almost all problems were ground related but I didn't think so because I was a meticulous builder. Anyway, he was kind enough to humor me and after weeks of testing and looking I was ready to listen to the poor ground thinking.

At his suggestion, I cleaned everything and added what I believed to be a worthless secondary ground. Not only did I ground the engine to the frame but added a second ground and cleaned everything up. It worked and my squirrely starting, charging and gauge issues went away. I may have also double grounded the gauges and even the trans to the engine but can't recall. It was silly stuff. So it worked for me when I would have bet otherwise and he said it was a typical issue.

That's my story and yours may be different and it may not be a ground issue but before you start tearing things apart search for the easy answers first. I have seen carbs rebuilt when the vehicle was only out of gas. In fact, I did it myself. You'll figure it out and later have a good laugh about it.

 

[gwdixon]

sixdogs:

Thank you for relating your experience. I mentioned earlier that I had a tractor (L3650) with a ground problem / starting issue that went completely away when a longer ground cable was attached to an engine bolt rather than the frame. I am not at all resistant to continue exploring the ground issue. In fact, it absolutely makes the most sense given the multitude of electrical problems present and their symptoms.

My past experience, like yours, was why a long ground was attached to engine in this M7040 problem. It made no difference. Continuity to the starter was tested and it was there.

I recognize a lot of you from years ago when I was more active on here and genuinely appreciate the sharing of your proposals. The M7040 has been a great tractor and generally trouble-free until now. Back to work on it today when the sun comes up - the barn doesn't have electricity. May have to crank up the generator for work lights.

 

[moship]

I don't have WSM for the M7040 to reference, but I do want to make you aware there may be slow burn fuses in the wiring circuit. Not saying the fuses are bad, but any termination point is a potential source of voltage drop. My Grand L40 has the slow burn fuses and are located near the battery and many folks overlook their existence in the wiring circuit.

Besides checking static voltage, I'd be testing voltage drop (under load) and narrowing down the circuit until the root cause is found. Hopefully you have a wiring diagram to reference.

Good luck!

 

[The Fred]

AMP draw the starter as you try to start the machine, also voltage drop the from the battery positive to the starter and see how bad it drops.

You know what the problem is you just have to narrow it down. Most starters draw around 200 amps as the engine is cranking. I want to guess your fully charged new battery has 800 or so available amps.

Good luck.

 

[moship]

Curious to learn if the OP resolved the issue and what was wrong.

 

[gwdixon]

Curious to learn if the OP resolved the issue and what was wrong.

Yeah, don't you just hate when you try to help someone and they never report back.

UPDATE: After a couple of days of continued frustration, I contacted the local Kubota dealer for a service call. They are 40 miles away and charge $145/hour starting when they leave their shop. At that point, I decided to accept some more frustration.

(FYI, the new battery has 850 CCA, 900 CCA is the WSM recommendation.)

Yesterday the starter was pulled to test it. What a PIA for anyone that has tried it. But...the starter tested fine and whirled away as designed. Re-installing was the same as removing but backwards...an "AIP". Why the bolt and nut threads are 100/cm and you can only turn the wrench 1/25 of a revolution is a good question.

Anyway, tightened up the starter and any and all other electrical connections that I could find. Cranked down hard the positive battery cable clamp and used a jumper cable to ground the bare negative to the engine. Time for one last try.

Turned the key and the jumper cable sprayed sparks and the engine started!!! Hooray!! Let it run a bit, shut it off, reconnected the negative ground cable and cranked it down to near stripping torque. It started right up again! Whew.

Yet to go out this morning and try to start it in the cold (Calif. cold) but thinking good thoughts. (Update on the update: started right up and several times afterwards. Solved.)

Conclusion: It must have been a loose connection. Did not do a scientific analysis of one fix at a time and then test so can't be sure what or where - likely the positive battery clamp since it could be tightened quite a bit. And don't really care at this point...it starts.