When you attempt to start the engine in your 5.7-liter GMC but all you hear is a clicking sound or your engine turns over very slowly, you likely have an issue with the starter. However, first you need to rule out the components that send power to the truck then test the starter to ensure the motor has not burned up. If you do not eliminate the battery and the ignition first as potential culprits, you cannot definitively determine if the starter is bad.
Remove the positive and negative battery cable connectors from the battery with a wrench and clean them with a mixture of baking soda and water. Remove all battery acid from the battery connectors then reconnect them securely. Try to start the GMC.
Connect jumper cables to your GMC's battery then connect the other ends of the jumper cables to the battery on a working vehicle. The ends of the cables are color-coded. The red cable goes to the positive battery connector, and the black cable goes to the negative battery connector. Turn on the working car and then attempt to turn on your GMC. If the vehicle starts, replace the defective battery.
Locate the two large metal posts on the back of the starter solenoid. The solenoid bolts onto the housing of the starter motor. Short out the two metal posts with a screwdriver by touching both posts together with the screwdriver's metal blade. Make sure you only touch the plastic handle to avoid getting shocked as sparking is common. Have a second person attempt to start the GMC. The motor in the starter housing should start up but not engage the engine. If it does start, the starter functions properly. Replace the starter solenoid. If it does not spin or it sounds very rough, replace the starter.
