Starting issue

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Elvism, Nov 19, 2017.

  1. Elvism

    Elvism Bobtail Member

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    Oct 29, 2017
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    I’ve got a 2013 Pete 386 with 550 ISX. When turning the key to start the engine bumps then stops then bumps. It does this a few times then starts as usual. It’s as if you are just quickly turning the key then back off again. Shop said starter but, that wasn’t the problem. New ignition switch maybe?
     
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  3. A5¢

    A5¢ Medium Load Member

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    Oct 30, 2017
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    Another place to look is all battery connections. Loose/ corroded cables/ terminals will cause a poor flow of power.
    There is also the positive contact bolt on the starter. The bolt is made of copper and when power is sent to the starter, the drive contacts the head on the inside of the starter. But it only contacts part of the bolt head and eventually wears away.
    Remove the positive cable at the starter, cover the terminal or disconnect at the battery. Remove the lock nut, push the bolt into the starter, turn the bolt one half turn, pull back out and replace the lock nut and all other connections.
    This is a temporary repair and will be good for many starts. Just get it fixed proper when you can.
    One very quick fix for starter brushes that are nearing their life's end, when they just do not have enough to contact the commutator, is to tap the starter with a hammer. The brushes drop down and make contact. It's a last ditch attempt, but when it's raining, or -35°, it's worth a shot. It'll get you rolling and off to a place to where proper conditions exist.
    The first suggestion is easy. I tossed in the others just as an FYI.
     
    xsetra Thanks this.
  4. Heavyd

    Heavyd Road Train Member

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    Yep, check all your basic battery and ground connections first. Sounds like the starter is starving for power or ground circuits. Sometimes, even when the cable is tight, the electrical connection is very bad due to arching. You might have to remove all of them and clean them with a brush.
     
  5. Dino soar

    Dino soar Road Train Member

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    I don't know if that truck has one or not, but if it has a separate starter solenoid the solenoid could be bad, have a loose connection, or a bad ground.
     
  6. GrapeApe

    GrapeApe Road Train Member

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    You have a starter interrupt relay, I'm not where sure on a 386, 388/389's are a micro relay behind the speedo/tach panel. Very common for them to lose the ground under load. The CECU controls the ground and if it has a poor connection, it'll do exactly what you describe. Voltage drops enough to turn off the CECU when the starter engauges, then it comes back on and repeats, so you get the bump - bump - bump effect. Step 1 is to jump that relay, if it starts normally with the relay jumped, you have a wiring issue on the CECU side. If it still does it with the relay jumped, your problem is on the starter/ignition switch side.

    On the CECU side, you have the clutch switch, neutral safety switch (which is just a jumper in the harness if you don't have one) and the starter thermal protection. Those 3 things tell the CECU that it's OK to ground the interrupt relay to crank. Those are all probably OK, the CECU is trying to let crank it. You will probably find that the CECU has a bad ground or power that is letting voltage drop, which is turn kills the ground at the relay.
     
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