Go BottomJohn Deere 750 starting problems
 | bobcrane
Join Date: Posts: 1 
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1999-12-18 11230
We have a JD 750 diesel we use for mowing the land around the church. Two seasons ago it began to give us fits when trying to start. When you turn the key you here the solenoid click but the starter doesn't move. After a few million tries eventually it would start.We replaced the battery and it worked once. We have now discovered that if you jump it with a car it cranks right over, no problem. The minute you stop it dies again.I put a meter on it and saw that the AC charge was coming out of the alternator, going into the transformer, but not coming out in any form. So I assumed the battery was not getting juiced up. But a fully charged battery will not kick it over either.The local guy said he has seen similar problems and has put on a jumper to bypass all circuitry and run a hot wire straight to the starter from the battery/key. I tried his theory by using jumper cables straight to the starter. It still did not move.Any ideas?Bob Craen
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| tom
Join Date: Posts: 1
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1999-12-19 11259
I'd check the condition of the battery ground cable, and especially where the
cable is attached to the engine.
That may not be the answer, but it's easy and should be done from time to time anyway.
I think there are probably some risks going directly the starter with jump cables. However, if you are, you still need a good ground. If the other jump cable is hooked to the battery negative terminal, and the battery ground is bad, then nothing is going to happen. A poor battery ground also prevents a battery from charging.
If you're going directly to the starter and you're sure the ground is good, I'd
guess the starter has to be suspect. Field windings become shorted. Armatures
develop low conductivity. There are various reasons why a starter motor might
draw a lot of current but develop little cranking power.
....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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1999-12-19 11263
Bob, your last sentence tells the story. If it cranks when you use a car to jump it....and does not crank when you use jumper cables directly from the tractor battery to the starter, then the conclusion is that the tractor's battery is dead. The car system has a little more push to it than the tractor battery, but not enough to make the difference between cranking fine and not cranking at all. Either you got a bad replacement battery, or it is not charging, or the charge is being drained off . I suspect that your voltage regulator is bad, and has gone bad in such a way that not only is it not charging the battery.....the portion that prevents the battery from discharging back through the alternator is bad as well. But don't overlook that it could simply be a bad replacement battery.
You can test this by completely disconnecting the battery from the Yannmar's circuit and recharging the tractor battery. It should be able to take a charge. And it should now start the tractor. Now disconnect the battery at the terminals and let it sit like this for a few days in the tractor. Reconnect it and see if it will start the tractor with the same enthusiasm. If so, the battery is good. Now let it set for a few days, but this time leaving the battery leads connected like they would be normally in the circuit... Try to start it now. If it will not crank over at all, replace the voltage regulator. (There is some chance that it is in the solenoid itself...but lower.)
Whatever it is, it is something simple. The testing that you have done so far shows that. Particularly the fact that it will start fine if jumped from a car. There is no need to bypass the entire circuitry. I suspect that when the local guy did this, what he actually did is eliminated that portion of the voltage regulator that was draining the tractor battery's charge.
And like Tom said: most problems are bad connections. Make sure that all the connections are good including the grounds. Next most common connection/starting problem is a corroded copper connector within the starter solenoid itself. But if jumping the tractor battery to a car battery starts your tractor, then the solenoid is not your problem. And probably your starter is good as too.............Roger L. ....
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| bobcrane
Join Date: Posts: 1
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1999-12-19 11275
Thanks to both for your replies! I should have mentioned in the first post I verified good ground on the battery. I did charge the battery for days but it was still connected to the tractor. I will take it out of the circuit and give it a shot.
A side note - when I first started this, the battery was showing 11.8 volts... not a full charge.
Bob ....
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| stogie5150
Join Date: Jul 2003 Posts: 1 Slidell,LA
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1999-12-19 11292
I just want to add that I have a Yanmar 2500 which is Identical to the 850 and it is notoriously weak in the charging system.The alternators dont put out much juice,so dont expect too much charging... ....
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| Vince
Join Date: Posts: 1
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1999-12-19 11294
Bob, Is it possible that you have more than one problem here. You seen to know that your charging system is not working correctly. and is it possible that your starter is also bad????? ....
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| bobcrane
Join Date: Posts: 1
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1999-12-19 11304
A couple of guys from church pulled the starter and took it in to be checked out. The JD dealer said it checked out OK.
Bob ....
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| Jocko
Join Date: Posts: 1
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1999-12-21 11349
I also have a JD750 and experienced a similar situation with starting problems. You need to make sure all of the interlocks are working properly (manual transmission neutral safety switch and seat sensor); in particular look at the seat interlock which was problematic on my tractor. Use a continuity tester to make sure they are working reliably.
When I purchased my tractor originally it would start regularly for a week at a time and then nothing for 10-20 tries with the key. Turned out after a bit of investigation the seat interlock was bad. ....
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| Alan
Join Date: Posts: 1
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1999-12-21 11358
I had a 950 with the same symptoms. JD dealer checked out the starter, it was OK. I finally tracked it to a "+" battery cable that was worn where it passed through a hole in some sheet metal where there was no protective grommet. It was apparently a part-time short, because replacing the cable fixed the problem. ....
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| Larry
Join Date: Mar 2004 Posts: 0 St.Davids
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1999-12-23 11428
I used to own a JD318 with a similar starting problem. JD sold me a starter relay booster kit that cleared up the problem. On the 318 the 12 volt line going to the solinoid from the key switch apparently did not provide adequate power to properly engage the solinoid on a regular basis. The relay kit used the solinoid 12 volt line from the key switch to engage a relay. The relay had a set of contacts that provided 12 volts directly from the battery to the starter solinoid. Your problem may or may not be the same. It would be easy to tell by running a jumper directly from the battery to the 12 volt terminal of the solinoid. If that clears up your problem then you should talk to your JD dealer about a starter relay kit for the 750. Or you could easily make your own. ....
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| bubber
Join Date: Posts: 1
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1999-12-24 11439
the problem you have the interlocking safety features of the tractor over a period of time creates what we call parasites in your electrical system the starter requires full battery voltage at the stater solenoid to engage stater you should contact your dealer about the instalation of a starter relay kit to solve your problem try it ....
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| bobcrane
Join Date: Posts: 1
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1999-12-24 11447
Thanks Bubber. I have heard others talk (including in this post) about the relay kit. It never made sense to me how such a beast would help since jumping the tractor caused it to start on the first key turn. But your explanation as well as the one above it make sense.
I have one question: where is the solenoid on the 750? I can hear a clicking in the shroud that covers the gas tank and dash area. Is it under there?
We fully charged the battery today and hooked it up to try as one of the earlier posts suggested. It would not do anything. The same battery after sitting a day still started my car! If I ran a hot wire straight to the bendix I could get it to engage but could not determine where the starter itself was being engaged off the switch.
So far the relay makes the most sense.
Bob ....
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| bo
Join Date: Posts: 1
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1999-12-25 11450
bob---Go for the relay- haven't been able to keep track of the posts and caught your last one and it seems as if it is the same problem that I had on my boat. The selonoid would click and nothing else would happen. Would tell you how to check the current flow to the selonoid and starter except you don't know where the selonoid is and neither do I. It seems that you are getting enough juice to click the selenoid but not enough to crank the much higher amp starter. In the case of my boat, I tested current flow, determined it was the relay, bought an after market diode suppressed relay for $13 installed same, time -one hour- problem solved and saved over 35 bucks by not buying oem Mercruiser. {Just jarring the "pay any price oem boys"} bo ....
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| bubber
Join Date: Posts: 1
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1999-12-25 11455
The reason that you can jump start your tractor from your car is that by connecting to car you are hooking your batteries in a series curcuit still using twelve volts but, have increased your starting amperage twice fold. Your question in regard to the location of the starter solenoid, is located internally on your starter. You have a purple single approx 14-16 gauge which sends the signal to the starter. When you locate wire and test curcuit you should have 95 percent or more battery voltage when you ingage starter switch. The add on solenoid usually mounts somewhere to the intake manifold. ....
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| larry willson
Join Date: Posts: 1
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1999-12-31 11632
Actually bubber came close but no cigar. When you hook jumper cables from your car battery to the tractor battery you are forming a parallel circuit. Voltage is constant throughout a parallel circuit. Current or amperage is dependent upon the branch of a particular parallel circuit. As for the actual cause of your starting problem bubber may be correct. Reduced voltage at the solinoid will cause it to malfunction and your starter will not engage. The reduced voltage at the solinoid may be caused by resistive contacts that have formed over time in the various safety interlock connections. Jump starting the tractor with a car probably causes a voltage increase in the then formed parallel circuit. This increased voltage is enough to compensate for the loss in the resistive contacts (via safety switches) between the tractor battery and the solinoid engagement threshold. Ergo, your tractor starts. Just buy the relay kit from JD and be done with it. ....
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