Diesel engines are notoriously smoky, producing much more blue, white, and black smoke than their gasoline-powered counterparts. The fundamental reasons for this are that diesels operate at higher pressures, with lower-purity fuel, and variable fuel-air ratios. This post covers the different types of smoke, and their (complicated) causes.
Almost every compression testing guide tells you to hold the engine’s throttle wide open during a compression test, but most won’t tell you why it may (or may not) matter.
Long and short-term fuel trim are very useful indicators of engine performance relative to the manufacturer’s specifications, but before we get into what they tell you, we’ll go over what they are.
Glow plugs are installed on many diesel engines to help with cold starts. They usually fail because of corrosion, overheating, mechanical damage, or metal fatigue, and their failure can cause a variety of problems. The easiest way to test a glow plug is by using a clamp-meter, though digital multimeters can also do the job, and glow-plug testers also work. We will cover the following topics in this post: What is a Glow Plug? What are the Symptoms of a Failing Glow Plug? How to Test Glow Plugs with a Clamp-Meter How to Test Glow Plugs with a Digital Multimeter How to Test Glow Plugs with a Glow Plug Tester Caution: Be careful to follow the glow plug manufacturer’s precautions when testing, as well as the test tool’s directions/manual, and read the vehicle (or other system) manual before doing any test.