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Testing Oxygen Sensors

There are a few different tests for oxygen sensors (also known as lambda sensors), some of which can be run without dedicated tools. The most effective tests tend to be done under normal operating conditions, on a sensor installed on an engine system, though there are some tests which can be done off-vehicle. You can test oxygen sensors with the following tools:

Caution: Be sure to follow the oxygen sensor manufacturer’s precautions when testing, as well as the tool manufacturer’s directions, and read the vehicle (or other system) service manual before doing any test. Oxygen sensors get very hot when in use, be careful!

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How to Test Glow Plugs

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:

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What are Wasted Sparks?

One of the questions we hear most often is ‘what is a wasted spark?’. Wasted sparks are also known by many other names, including ‘waste sparks’, ‘exhaust sparks’, which adds to the confusion.

Wasted sparks are produced in four-stroke (Otto cycle) engines, where the ignition system produces a spark on every revolution. This is called a ‘wasted spark’ because half of the sparks are created between the end of the exhaust stroke and the beginning of the intake stroke, where there is nothing to ignite, so those sparks are wasted. Wasted-spark systems are simpler than conventional distributor ignition systems, which makes them lighter, and more reliable. Wasted spark systems are most common on small one or two cylinder four-stroke engines, such as those found on lawnmowers, marine outboards, go-karts, and some generators.

Conventional Four-Stroke Engine (Otto) Cycle

  1. Intake (TDC->BDC)
  2. Compression (BDC->TDC)
    SPARK!
  3. Expansion (TDC->BDC)
  4. Exhaust (BDC->TDC)

Wasted Spark Four-Stroke Engine (Otto) Cycle

  1. Intake (TDC->BDC)
  2. Compression (BDC->TDC)
    SPARK!
  3. Expansion (TDC->BDC)
  4. Exhaust (BDC->TDC)
    SPARK!

Why Most Engines Don’t Use Wasted Sparks

Creating and sustaining a spark takes a little bit of energy, usually about 50mJ per spark, but ignition systems are usually only about 1% efficient. Ignition systems waste a lot of energy in powering their various components, so their total energy consumption is about 5J per spark. A small two-cylinder four-stroke engine idling at 1000 RPM will use about 50mL (1.7 oz.) of gasoline per hour just to create ignition sparks. Since waste sparks use almost as much energy as ignition sparks, a waste spark engine will waste almost as much fuel again! And this is just at idle!

Because waste sparks consume energy without producing anything useful, they reduce the engine’s efficiency and power output, while increasing fuel consumption (especially at low power settings). This decrease in fuel efficiency and power output is not acceptable unless the engine’s weight is extremely important.

Do Two-Stroke Engines Have Waste Sparks?

Two-stroke engines do not have wasted sparks, because they do not have an exhaust stroke. On a two-stroke engine, there is a compressed fuel-air mixture to ignite at top-dead-center on every revolution. This simple park timing makes distributors unnecessary on most two-stroke engines. That being said, some large and slow two-stroke engines do have distributors, but these are rare; we have only heard of a few still in use.

Two-Stroke Engine Cycle

  1. Intake/Compression (TDC->BDC)
    SPARK!
  2. Expansion/Exhaust (BDC->TDC)

Distributor-Less Ignition Systems (DIS)

‘Distributor-less ignition’ systems (also known as distributorless ignition systems) are those without a conventional high-tension distributor for spark timing. Before the advent of computer-controlled (ECU and ECM) ignition systems, ‘distributor-less four-stroke’ usually meant that the engine had a waste-spark system, with the spark plugs directly connected to a magneto. Modern engines use ECUs and ECMs to control coil-on-plug and coil-near-plug modules, which have one coil pack per cylinder, and no distributor. The bottom line is that distributor-less isn’t what it used to be!

That’s All!

If you’re looking for a fast, easy-to-use, and comprehensive way to test an ignition system, check out our GTC505 Engine Ignition Analyzer.

If you have any feedback for us, or ideas for topics we should cover in future blog posts, please send us an e-mail.

How to Use a Battery Tester

Most battery testers have two clips (or test leads), you first attach these to the battery’s terminals (connectors), then you press a button (or switch), and a few seconds later, the tester displays or prints a result indicating the battery’s condition. The details of you use a battery tester depends on what kind of battery you have, the electrical system it is connected to, and which tester you plan to use. Some battery testers require disconnecting the battery from the vehicle, while others have different limitations. Most battery testers only work on one, or a few different types of batteries. We describe how to use five different battery testers below:

  1. Carbon Pile Battery Testers
  2. Hand-Held Battery Load Testers
  3. Battery Hydrometry Testers
  4. Battery Conductance Testers
  5. Multimeters

Caution: Be careful to follow the battery manufacturer’s precautions when testing, as well as the tester manufacturer’s directions, and read the vehicle (or other system) manual before doing any test, or even disconnecting the battery.

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