Q: Bad Starter?

asked by on March 23, 2018

Okay, have an 2003 Mercedes S55 AMG, i think i have an bad starter. Brand New battery, Battery terminals new and tight, used circuit pro to test circuitry, and it showed circuity is grounded and okay, Used my Power Probe to test Power and grounds at the starter relay, the 87 on the relay goes directly to the starter to power it up i sent 12 volts using the power probe and the starter "bumps" and the engine moves a few inches every time but it does not fully start. Check the connections at the starter itself, I have continuity and it appears everything is grounded, checked with power probe and circuit pro again. Now the starter is 3 months old. Just to be clear checked for 12 volts going from the igniton switch to the starter, 12 volts coming from the battery itself to the starter, My question is if the starter is bad why would it move the engine at all? Can there possibly be something else going on? Bought starter as a rebuilt one pretty cheap, any answers are greatly appreciated

My car has 165000 miles.
My car has an automatic transmission.

Testing for voltage alone, or even continuity, on a circuit is not sufficient. You should test for any voltage drop in the starter circuit to be sure that there is not high resistance "somewhere" in the circuit that is causing the voltage to drop once the circuit is loaded. Once voltage drop is ruled out, if there is power to the solenoid, and the high amp cable is connected to the starter motor (with no voltage drop), and yet the starter does not function, the starter is faulty and should be replaced. MB dealers might sell factory rebuilt starters. If so, that will be a preferred option for you. You can also purchase a new starter from the dealer and going that route all but guarantees that you will get a functioning, high quality, reliable unit. If you desire a diagnostic of the starter motor/circuit, and repairs/replacement if warranted, please schedule service via YourMechanic’s starter motor service request page. If you desire an OEM (new) starter, the mechanic will arrange for that but the cost of the part will likely be higher than if you purchase a rebuilt starter. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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