1. Check the obvious:
* Battery Connections: Even with a new battery, loose or corroded cables can prevent starting. Make sure the terminals are clean, tight, and properly connected. Use a wire brush to clean any corrosion.
* Fuses: Check the fuse box (usually under the hood and inside the cabin) for any blown fuses, particularly those related to the ignition system or fuel system.
* Security System: If your Tahoe has an aftermarket or factory alarm system, a malfunction could be preventing the engine from starting. Try disarming the system.
2. Ignition System:
* Ignition Switch: A faulty ignition switch can prevent the engine from receiving power. This is a common problem in older vehicles.
* Ignition Coil: This part provides the high voltage needed for the spark plugs. A failing coil will prevent the engine from firing.
* Spark Plugs and Wires: Worn or fouled spark plugs and damaged wires can prevent a spark. Check their condition and replace them if necessary. This is a common cause.
* Distributor (if applicable): Older vehicles might have a distributor; check its cap and rotor for cracks or damage.
3. Fuel System:
* Fuel Pump: A faulty fuel pump won't deliver fuel to the engine. You might hear the pump prime when you turn the key to the "on" position (listen near the fuel tank). If you don't hear it, the pump might be bad.
* Fuel Filter: A clogged fuel filter restricts fuel flow.
* Fuel Injectors: Problems with the fuel injectors can prevent fuel from reaching the cylinders.
4. Other possibilities:
* Neutral Safety Switch: This switch prevents starting unless the vehicle is in Park or Neutral. Make sure the shifter is correctly in one of these positions.
* Starter Relay: While you said it cranks, a weak starter relay might still be insufficient for a start.
* Cranking speed: If the engine cranks slowly, it may point to a weak battery (even a new one may have been damaged in transit or installed incorrectly) or a faulty starter motor. A low cranking speed can indicate a battery not holding a charge well.
* Computer/ECU Problems: A problem with the Engine Control Unit (ECU) can prevent the engine from starting. This is less likely, but possible. You would likely need a diagnostic scanner to check this.
Troubleshooting Steps:
1. Start with the easiest checks: Battery connections, fuses, and the neutral safety switch.
2. Listen for the fuel pump: Does it prime when you turn the key to the "on" position?
3. Check spark: A simple way to check for spark is to remove a spark plug wire, ground the end of the wire to the engine block, and have someone crank the engine while you look for a spark. (Be careful not to touch the spark plug while doing this).
4. If you are not comfortable working on your vehicle, take it to a mechanic. They have the tools and expertise to properly diagnose the problem.
By systematically checking these areas, you should be able to narrow down the cause of the starting problem. Remember safety first, disconnect the negative battery terminal before working on any electrical components.
