No Start 1: Checking For Spark
The very first thing you need to do is check for spark and the presence of fuel. Both of these tests should be done simultaneously if possible. As mentioned before, usually one of them will be missing from the mix.
The idea behind checking for spark (with a spark tester) is to see if all of the 8 engine cylinders are getting spark.
- Check that the 8 cylinders are getting spark with a spark tester.
- If spark exists in all 8 cylinders, this then confirms that:
- The distributor cap is good.
- The ignition coil is good.
- The ignition control module is good.
- The crankshaft position sensor is good.
- If there's no spark present in all 8 cylinders:
- The distributor cap could be bad.
- The ignition coil to distributor cap high tension wire could be bad.
- The ignition coil could be bad.
- The ignition control module could be bad.
- The crankshaft position sensor could be bad.
Testing the distributor cap, the ignition coil to distributor cap high tension wire, the ignition coil, the ICM, and the crank sensor can by done by the do it yourself-er (DIY'er) and the following tutorials will help you test the ignition system:
- How To Test A Misfire / No Spark No Start Condition (at: easyautodiagnostics.com).
- How To Test The Crank Sensor (GM 4.3L, 5.0L, 5.7L).
- How To Test The Camshaft Position Sensor Diagnostic Trouble Codes: P0340, P0341.
No Start 2: Checking For Fuel
Lack of fuel reaching the injectors is the other major and common cause of a no start Condition and that's usually caused by a bad fuel pump.
The fuel pump usually fails in one of two ways (in the pickups and SUVs covered in this article), it either fails completely and doesn't send any fuel to the engine or it still runs, but doesn't send enough fuel to start or keep the engine running.
Keeping the two modes of failure in mind, the most accurate way of testing the fuel pump is with a fuel pressure test gauge.
- When testing the fuel pump with a fuel pressure test gauge, you'll get one of two results: correct fuel pump pressure, or low/no fuel pump pressure.
- If the pressure gauge does register the correct fuel pressure, this confirms:
- The fuel pump is getting power and Ground.
- The fuel pump fuse is good.
- The fuel pump relay is good.
- If the pressure gauge DOES NOT register the correct fuel pressure, this usually means:
- The fuel pump is bad.
Testing the fuel pump is something you can do. Depending on whether your vehicle has throttle body fuel injection or the ‘Spider’ fuel injection system, the following tutorial will help with this test:
- Troubleshooting the fuel pump (GM 4.3L, 5.0L, 5.7L) (for ‘Spider’ fuel system equipped vehicles).
- How To Test The Fuel Pump On GM TBI Fuel Systems (for throttle body fuel injection fuel system equipped vehicles).
No Start 3: Checking The PassLock Anti-Theft System For Problems
A failure in one of the Passlock system's components will cause the engine to start and then stall after a few seconds.
This is due to the fact that the PCM, in your GM pickup or SUV, has disabled the fuel injectors.
Unfortunately a Passlock failure mimics a failed fuel pump problem and usually makes the vehicle owner think that the fuel pump has failed.
Here are the basics of what you should do to find out if the Passlock system is the one keeping your pickup or SUV from starting:
- Check fuel pressure with a fuel pressure test gauge.
- If fuel pressure is at specification, the next step is to check for spark.
- If fuel pressure is NOT at specification, then the Passlock system is not the cause of the no start condition.
- Check for spark with a spark tester.
- If spark is present at all 8 cylinders, the next step is to see if the engine starts with starter fluid.
- If spark is NOT present at all 8 cylinders, then the Passlock system is not the cause of the no start condition.
- Start the engine with starter fluid.
- If the engine starts (even though it'll stall after the starter fluid you sprayed into the throttle body gets consumed), then you have confirmed that the Passlock system is keeping the engine from staying running.
The Passlock system leaves specific trouble codes in the PCM's memory when a failure occurs in one of its components. Unfortunately, you need a professional level scan tool (the ones that cost US$ 2,000 +) to read these codes.
This doesn't mean you can't correctly pin-point the Passlock system as the culprit behind your pickup or SUV's no start condition. For more info on this, check out the Passlock symptom chart in this tutorial: