There is a multitude of possibilities that cause a no-start problem in a 1999 GMC Sierra. The best way to attack this kind of a problem is systematically, through the process of elimination. Start with the most common problems. If the problem is computer related, the check engine light will be illuminated.
Attempt to start the vehicle. If it starts with difficulty, check to see if the check engine light is on, indicating a computer control or sensor problem. Listen for the starter to energize as you attempt to start the engine. If the engine turns over when the starter is energized, the problem is not with the starter. If it fails to energize and no sound can be heard, the problem is electrical.
Plug the code scanner into the OBD port under the left side of the steering column. Turn the key to the run position. Press the “Read” key on the code scanner. Make a note of the code displayed on the scanner, and cross reference this code with the accompanying code sheet for a definition of the problem. Repair the problem and reset the computer by pressing the “Erase” key.
Check the battery for the proper voltage. Connect the voltmeter’s black lead to the negative battery terminal and the red lead to the positive battery terminal. The voltmeter should display 12.75 volts or very close. If it does not show 12.2 volts or higher, start the engine and re-check the voltage to see if the alternator is functioning. With the engine started, the voltage should rise to between 13.8 and 14.5 volts. If it does not rise, the alternator is bad--shut the engine off.
Have a helper start the engine while you watch the voltmeter. If the voltage drops below 10.5 volts when the engine is started, the battery has a bad cell and must be replaced.
Check the starter fuse in the fuse relay box on the driver’s side fenderwell if the starter does not energize. If the fuse is good, check the terminals on the battery for corrosion or looseness, repair as necessary and try the starter again. Check the starter for battery power at the large-diameter wire terminal on the starter solenoid by placing the voltmeter’s black lead on a good ground and probing the terminal on the solenoid where the large diameter wire is connected. The voltmeter should show battery voltage. If not, the problem is the wire or battery terminal.
Check the small diameter wire on the solenoid, which is the ignition switch wire. This wire should have power only when the key is in the start position. Have a helper turn the key to start, and probe the small wire for power. If it has power the starter is bad. If there is no power the ignition key is bad.
Check the engine for fuel starvation. Take the gas cap off and listen for the fuel pump to energize when a helper turns the key to the run position. The fuel pump will only run for 2 seconds at a time if the engine is not started. Cycle the key on and off in 5-second increments. If you cannot hear the fuel pump, check the fuel pump fuse located in the fuse relay box under the hood. If it is good, remove the air duct at the throttle body using a screwdriver.
Open the throttle by pushing the linkage with your hand, then spray a 3-second shot of carburetor cleaner into the throttle body. Install the air duct temporarily on the throttle body. Try to start the truck. If the truck starts and runs for a second or two where it wouldn’t previously, the fuel pump is bad. If it does not run, the problem is elsewhere.
Check for water in the oil. Look at the dipstick and see if it looks like mud (oil mixed with water) as a result of a blown head gasket. Remove the oil cap and check for the same thing. Remove the radiator cap and look for oil in the antifreeze. If oil is found in any of these locations, the head gasket must be replaced.
Remove a spark plug wire from the spark plug and insert the spare spark plug. Lay the spark plug on the intake manifold with the electrode touching a good ground. Have a helper crank the engine while you watch the spark plug. When the engine is cranking, a blue spark should be visible at the electrode. If no spark is evident the problem is in the ignition circuit.
Check the coil for power at the positive terminal. Connect the voltmeter’s black lead to a good ground and probe the positive side of the coil with the red lead. With the key in the run position there should be battery voltage at the coil. If there is no voltage a wiring problem is present. If it does have power, either the coil or spark plug wires are faulty.
Check the coil wire for continuity. Place the volt/ohmmeter into the ohm mode. Place the black lead on one end of the wire and the red lead on the other. There should be no more than 18,000 ohms. If the resistance is higher, replace the plug wires, including the coil wire.
