1988 Volvo 740 NO START Case Study

Ignition System Testing Summary And Useful Links

Well, we've come to the end of the tale. As you have read and learned in this Volvo 740 case study, these ignition system tests are not complicated or difficult to perform. All that there is to it is to follow a simple and basic, yet flexible testing structure. This testing structure is explained in more detail in several articles in this site. At the bottom, you'll find links to those articles and others that might be of interest.

Every vehicle that you'll deal with, with a no-start condition, will have a different thing causing it. A NO-START diagnostic is a very fluid and dynamic process. This shouldn't worry you in the least. It's what makes this job fun and interesting (til frustration sets in and you want to torch the car).

So knowing the basic working theory and some tests, you'll be able to figure out the problem and its solution.

If you haven't learned to read a wiring diagram yet, make it a priority to do so. This skill will give you the advantage and the edge to solve almost anything that will cross your path.

Test By Test Diagnostic Summary

The following is a summary of the most important aspects and key points of this NO-START article:

1. I started by checking for spark.
   • At the spark plug wire.
   • At the ignition coil.
2. Since the results for the two tests above were: NO SPARK, I then:
   • Checked for the presence of 12 V at the ignition coil's positive terminal.
   • Checked for the presence of the Switching signal at the ignition coil's negative terminal.
3. From the results above I then tested for fuel injector pulse with a Noid light.
   • This was to indirectly verify the presence of the crankshaft position signal.
4. From these results, I then:
   • Checked for the presence of 12 V at the ignition control module.
   • Checked for the presence of Ground at the ignition control module.
   • Checked for the presence of the Triggering signal at the ignition control module.
   • Checked to see if the module was switching the ignition coil ON and OFF (Switching signal).
5. From the results of all of the above tests I was able to come to the conclusion that:
   • That the ignition control module was bad.

This basic structure is flexible. The next test (or step) will depend on the results you obtain from the previous test. The really cool thing is that this flow of specific tests apply to almost everything on the road. So whether it's a Volvo, a Volkswagen, a Ford, a Dodge or a Chrysler, or a Chevrolet, a Buick, a Pontiac, or whatever, you'll be able to use these tests.

Links To Ignition System Articles

For further reading, I recommend the following articles (within this site) that may shed some more light on this subject.

1. NO-START diagnostic tips.
   • The Basics Of Testing A No-Start Condition
2. Ignition system basics.
   • How Does An Ignition Coil Work?
3. Testing an ignition coil pack.
   • How To Test A Distributorless Type Ignition Coil Pack.
4. Testing a Coil-On-Plug ignition system.
   • Coil-On-Plug Testing Tips and Techniques.
5. Case study of a does not crank condition.
   • How To Test A Does Not Crank Condition -Case Study (GM 3.8L)
6. Case study of an ignition misfire diagnostic.
   • Carbon Tracks Are A Common Cause Of Ignition Misfires.
7. The HEI Spark Tester.
   • The HEI Spark Tester (The Best Spark Tester On The Market).