JD 770 No Start/Power

[fishmen222]

Have a 1992 JD 770. 12.8v at battery, 12.7 at starter and all fuses are good (that I found). I have checked almost all connections...and nothing. I went to start it, the pump primed and glow indicator turned off as usual and then it all died. I doubt a safety switch because I should still have power to the instrument cluster. Checked battery ground resistance...all is normal. There is a black rectangular relay but I do not have a clue what it controls. On a side note, I have had to smack the starter the last few months to start, but shouldn't I still have power to the panel if the starter is bad? Relay? Starter? Ignition switch? Any thoughts would be greatly appreciated!

Thanks folks and have a great Labor Day.

 

[jd110]

Check the voltage at the starter when you attempt to start. If voltage is still good when trying to crank, the battery connections are probably ok, but if you lose voltage, then there is a bad connection somewhere or a cable may be bad. There is a fusible link at the starter that could be bad.

 

[TedLaRue]

This may sound like a silly suggestion, but try removing the existing battery and jumping from your car or truck battery to the battery cables on the tractor (or else replace the existing battery with a known good battery). Don't just jump to the existing battery; take the existing battery out of the circuit.

I had a similar experience, and all of the symptoms pointed to something other than the battery. I even had a charger with 50 amp "Engine Start" connected to the old battery. When I removed the old battery and jumped from my truck battery it started. Another JD owner with a similar machine told me he had a similar experience.

When you figure it out, please post the results so future readers can benefit from your experience.

 

[grsthegreat]

Have someone check the voltage as you try to start the tractor. just cause you see 12.7 at rest doesnt mean it has the oomph to turn over the diesel under load.

My old 870 did this to me, and i found that after i turned the key, i got under 6 volts at the starter. Even though the lights would work ... though dim.

A new battery solver my problem

 

[TedLaRue]

The suggestions by jd110 and grsthegreat are excellent suggestions, and what I tried in my case, but you may not see any voltage at the starter when you try to crank. That would suggest a safety switch or something else, but not the battery. As I posted above, try eliminating the existing battery and using a known good battery.

 

[Coyote machine]

Put your VOM on the battery posts at the cable connections and see what reading you get while turning the key to crank.
If voltage drops below 12 volts but it won't crank over you probably have a dead cell or battery is possibly toast.
Don't jump to conclusions about part replacement unless you've confirmed each step of the way. Sounds like starter/solenoid could be problematic too, but first rule out connection issues, ground cable from battery to frame, battery under load, specific gravity across battery cells, etc. How old is battery? How many hours on tractor?

 

[fishmen222]

Thanks guys. I will bypass the battery tomorrow. I was leaning towards the battery and/or cables, but all were replaced last year. What gets me, is shouldn't I at least have power to the panel with 12.7 at the starter? I have had weak batteries/connections before and it simply would not start...not a zero power situation like I have. I have absolutely no power to anything...dead as a doornail, yet the battery seems fine. Thanks again!

 

[fishmen222]

OK now. At a loss as I have not seen this before. Took the battery and cables out of one of the boats...started perfect and seconds later shut down as before. No dash, pump..anything. Fusible links and fuses are fine. No noted rodent damage. Cannot help but think that the need to smack the starter the last year to start is not related. I know solenoids stick, but would they cause a total power outage? Thanks again folks!

 

[Coyote machine]

To solve this you need to keep it simple and do one test at a time and assume nothing as you eliminate possible causes of the problem(s).
Do as already asked and put your meter at the battery and read what it does when the engine cranks, if you can get it to crank. 12.7V or whatever, means nothing until you put a load on the battery and then you get a reading of what the voltage drop is while cranking or when running or both.
Let's say you have a problem with your starter and or solenoid at the starter for illustration purposes. Once you crank the engine, with amps, (current) flowing from the battery, passing to the starter solenoid through the ignition switch to the energizing wire on the solenoid a circuit is completed. That is the start circuit initiated by turning the key at the ignition circuit.
By seeing what voltage drop is created by turning the key and reading the meter this will tell you if the battery has enough voltage to turn over the starter, or not. Your starter may not be bad, but the solenoid may be weak, or you may have worn brushes inside the starter, or whatever of a list of possible problems.
Ideally you would and certainly can remove your existing battery and have it load tested and check the specific gravity and electrolyte level of each cell in it to determine what it's condition is OUTSIDE of the tractor. If it fails any of the above mentioned tests it is time for a new battery. This may end up being the case- BUT it may not be your only problem.
Let's say the battery is toast. Get another one and install it and then continue to diagnose and rule out other problems like your starter/solenoid, etc.
Do not worry about 12.7 or whatever at the starter. Do worry about what the battery can put out under load. Post back results of above mentioned tests.

 

[Henri88]

Could also be your ignition switch.