puzzled, 85 6.9 barely cranks
 

Hi all, I'm pretty new to diesel. My truck is an 85 F250 4wd w/ a 6.9. Last week I had to jump it due to a low batt, i figured it was due to me loading and unloading the cab w/ the door open too long. Then no problems over the weekend. Night before last I pulled it up to the garage to replace the fuel return caps, hoses etc... for a fuel leak, when I was done, It would barely crank over then not at all. I have charged the batteries, checked water levels, cleaned all related terminals and load tested. Load test was 12.5..cranking it will drop to 6v after 1 partial revolution. then back up to 12.5. I also tried two known good batteries, one red top optima and a deep-cycle marine batt. Same result. since I cant move the truck, unfortunately I can't get my wife's car out of the garage. Luckily she is very understanding but i feel it has gone on too long now. If any one has any thoughts or ideas i would appreciate it.
Thank you for your time
Dan-

check the connections at the battery and starter

Not a good idea mixing battery types. They run gear reduction starters I believe, but that doesn't mean the field doesn't ever go bad. Along with that, brushes and the solenoid cap. Drop the starter and have a look at the brushes. If you find one in question, replace em all, then look at the solenoid cap.

I checked and cleaned all starting related connections. then I checked for resistance, none was found. The only thing that was questionable was a loose + on the starter, so as with all others I removed, cleaned and re-installed it.
I have not removed the starter at this point but since the temp outside the garage is around 37deg or so, I'll wait another night and pull it after work tomorrow.
Thanks for the thoughts on my problem.
Dan-

Three brushes are 1/2", one is 1/8". I agree to replace them all. I'll try to find/install them and let you know what I come up with.
Dan-

How'd it go?? :pca1:

did it work any updates:pca1:

Do the brushes, may as well grease all the bearings, and replace the solenoid and the starter drive. :tu:

Good news,
The starter was the problem and better still was
the recipt from the previous owner for a statrer with
lifetime replacement. That starter was paid for with cash
so it may as well have had my name on it for the warranty.
It cranked over great, I bled out the injectors(the reason this all
started) fired up and runs. I'm happy, the wife has her car out
of the garage, so she's happy.
Thank you for your advice and willingness to share it.
Dan-:tu:

Good deal it worked out. :tu:

Will close the thread.