If you think CIS fuel injectors can just be ignored, think again. Sure, your gas engine will continue to start and run “ok”, but you may find that it is not producing the power it once did nor the fuel mileage it once delivered. You may also notice that it does not start or idle as smoothly as it once did. Maybe it starts up and then quits the first time you start it cold. Or, maybe it will not start hot until you let the engine sit for a while. These can be signs of ill spraying or poor sealing fuel injectors.
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The only reliable and safe way to know for sure how they are performing properly is to remove them from the engine and bench test them with a pressure tester. We know there are some that will claim you can test them out of the holders while the engine is running. We strongly discourage this. Doing so can be quite dangerous as atomized gasoline can easily ignite with the smallest spark. A pressure tester such as the one we sell here can also be used to clean the internals of the injectors if they fail the initial pressure tests. In many cases, but not all, cleaning with pressure strokes and the proper cleaner can restore an injector to proper working condition.
In this step-by-step video (using a 1990 M104 6 cylinder CIS gas engine) Kent will explain and demonstrate the following:
- Importance of properly working CIS fuel injectors
- How to recognize if your engine has CIS injection system
- How easy it is to remove this type of fuel injectors
- Diagnosing potential air leaks at the injectors
- Types of seals used to prevent air leaks
- Removing the old hard seals from the injectors
- Two different types of injectors shown
- What you can and can not do to service these injectors
- Where to do the testing
- Type of fuel to use
- Safety precautions
- How the tester is set up
- Other preparations for testing
- Live tests showing results of all six injectors
- Recording your results
- Setting up to clean the injectors
- How to pump clean each injector
- Results shown
- 3 things to look for with testing for a good injector
- How to get a balanced set of injectors
- Showing what a new injector can do
- Tips on installing the injectors back into the engine
- Ongoing service recommendations
PLEASE NOTE: Testing and cleaning CIS injectors for 4, 6 or 8 cylinder engines are done the same way. The type of holders used and precisely how they are removed form the different engines from 1976 to 1983 can vary. General principles are the same but the actual details on removing the fuel injectors can vary slightly from engine to engine. This video only shows details related to removing the CIS injectors from the 1990 to 1993 M104 engines with CIS. If you have an M103 the holders and procedures are almost exactly the same. Some models of V8 engines have different types of holders so the removal sequence will be different from what is shown in this video.
Step-by-step injector replacement is not show as this is very straightforward once you have removed your fuel injectors. Kent does share tips on how to successfully install the new seal and replace the injectors back into a M104 engine.
Total Run Time: 32:09
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