No spark

  • 1 POST
  • 1993 GMC SIERRA
  • 5.7L
  • V8
  • 2WD
  • 300 MILES

I was driving my truck when all of a sudden it dies. Now I get no spark it has power to coil but no power back. I have replaced coil and cap n rotor still nothing. What would it be?

Do you
have the same problem?
Saturday, August 20th, 2016 AT 11:23 PM

1 Reply

  • 21,085 POSTS

You need to find out what some of the other systems are doing also.

All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can only be tested during the failure. Any other time and they will simply test good because the problem is not present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That is what we have to look for.

These are the basics that need to be tested and will give us the information required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.

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Sunday, August 21st, 2016 AT 4:22 AM

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