If you have a 5.7 Vortec engine and it is not getting any spark, there are several things that can cause the issue.
This includes the fuses, crank sensor, cam sensor, distributor, ignition module, plug wires, and rotor.
With the many things that can cause a no spark issue, each component will need to be tested or replaced to find the cause.
Having a good spark plug test tool is a good idea as they are low-cost and easy to use.
Many mechanics will hold a spark plug wire close to a ground to see if there is a spark, that does work, but it is much safer and easier to use a low-cost spark plug test tool.
Here is an example spark plug test tool on Amazon
Fuerdi Ignition Spark Plug Tester Wire in-line Diagnostic Tools Automotive Auto Detector Coil Ignition System Test for Automotive
8 Causes and Fixes for 5.7 Vortec No Spark from Coil
- Crankshaft Sensor
- Camshaft Sensor
- Spark Plug wires
- Bad Coil
- Ignition Module
The ECM controls many things, including the spark.
Wires were causing a ground problem which was blowing a fuse and causing no spark along with other problems.
Once the shorted wires were fixed, the truck got spark and was back up and running.
When it goes bad, it also causes issues with the spark.
The Camshaft Sensor on the 5.7 Vortec is located in the distributor under the rotor cap.
Often, very old failing spark wires will have a few that work and a few that don’t.
An old bad coil wire going to the distributor will cause a no spark problem.
If it looks to be in bad shape, it is usually best to replace it.
Each plug wire can be tested along with the coil wire going into the distributor.
Like the rotor, if it is old and worn out, it is usually best to replace it.
Many mechanics will test if by holding it close to the ground having a helper crank the truck over and see if a spark jumps to the ground.
Using a spark light tester is much safer from accidentally getting zapped.
The main thing is to see if the coil is sending out a spark.
Keep in mind while rare, sometimes a spark can be seen but is weak, which can cause no-start issues.
I have seen this a few times where the coil sends out a spark, but since the spark is weak, it causes problems.
If the coil is very old, it may be best to replace it, but usually, when a spark is seen, the coil is good.
On the 5.7 Vortec it is located on the top left side of the engine.