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Peterbilt starter issues

bsamot69 · 2021-11-23 16:16

Yes. Another piece of equipment...Peterbilt dump truck, believe it is 379. I got a message it is not cranking. At truck, I check batteries, 2 in this unit, both have good voltage, 12.8 and load test good. It would click when dash button pushed. I went to starter and tried jumping the s terminal and battery connection on the solenoid looking thing mounted to starter. It just clicked. I noticed a solenoid on fender well but wasn't sure it's function. I have since read it sends voltage to the starter. I then connected battery positive jump cable to starter motor lug and ground cable to negative lug then touched negative cable to battery negative expecting the motor to run. Nothing. I pulled the starter and cleaned up the terminals and connected battery to starter and remote switch to s terminal and push button. The solenoid clicked a couple of times, the gear didn't move nor motor run. Connected direct to starter motor and touch negative to negative lug on starter. Get a spark but no motor run. I'm using a new battery for these tests am I missing something here? Is this a bad starter? Am I connecting.my cables properly? This huge piece of metal, heavy and cumbersome has me second guessing myself. I checked the resistance between the starter motor positive lug and the ground lug on front of motor. The resistance is 0 ohms . I expected a much higher value. Any suggestions are greatly appreciated.

Replies11
  1. #1Jonas3022021-11-23 19:08

    If your direct on the starter hot and ground it sure sounds like a bad starter to me You may be able to get a gear reduction starter as replacement and save a lot of lifting weight going back in like lift with one hand light

  2. #2Delmer2021-11-24 00:10

    Check the voltage when you're "clicking", voltage doesn't lie, if the voltage going into the starter is the same as battery voltage, you have a bad starter.

  3. #3Coaldust2021-11-24 00:32

    Second that thought about the Prestolite gear reduction starter. Plus, no core charge. Surprisingly good deal for the money, too. Way easier to install.

  4. #4Former Wrench2021-11-24 15:55

    Remember that a 12 V battery has 2.2 volts per cell. The volt/olhm gauge needs to read 14.2 to mean the batt is carrying a full charge. Anything less is a dead cell.

  5. #556wrench2021-11-25 10:50

    Maybe 13.2 volts? if the specific gravity is good? Also depends how the batteries load test after the surface charge has been removed

  6. #6Junkyard2021-11-25 11:52

    The gear reduction units are nice but don’t last long if started with low voltage. They can’t take the amperage spike. My haul truck has one and I have to keep a tender on it if parked for long periods of time due to all the small draws. A few low voltage cold weather starts and she’s always a slow hard initial crank. Good batteries, good cables and clean terminals.

  7. #7Blue Pete2021-11-28 13:45

    I just had a similar problem. Replaced the starter and it worked for a few days. Then did it again. When I went through all the cables, the ones to the disconnect in the cab were loose.

  8. #8bsamot692021-12-01 21:41

    It turns out the solenoid on starter was junk. Went ahead and replaced the entire unit. Figured it was all the same age, old. I really didn't want to be pulling that monster out again.

  9. #9DMiller2021-12-08 18:34

    MT42 is not a Bad weight starter, MT 50 was a HOSS, older MT40s were just awkward. Need to try wrestling a MT50 out of a Crawler in dead of winter with snow blowing under your coat. Second a Hard check of charging rate and having batteries Load Tested at a Shop.

  10. #1059 North2021-12-08 19:16

    For sure on the MT 50!

  11. #11DMiller2021-12-09 04:42

    Those and the original style 15/16 six point 5/8 USS bolts made life less than enjoyable.