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I have a 2005 jeep grand cherokee 4.7L V8 engine with 70,000 original miles. Plan on performing an injector balance test with an OTC 3398 fuel injector balance tester. It has several settings including 1 pulse, 50 pulses, and 100 pulses. Which setting should I use for an injector balance test and why?
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I like 50 pulses. A single pulse will not show much other than the injector is capable of clicking. To see a real pressure difference you need multiple pulses. You could use 100 but it seems a bit excessive and depending how long the pulsewidth is could drop the pressure so low on all of them that it would be difficult to get a real valid result out of the test.
Plan on pulling your plugs out. Eight cylinders pulsing 50 times each means 400 pulses worth of fuel in the intake and you don’t want that taking a chance of hydrolocking or getting down into the cat when you go to start up. Much better to just hold the throttle open and crank the motor to throw the extra gas out of the cylinders.
Are you doing this test because you have an issue or just a preventative check on how the injectors are performing?
Doing the test as a preventative measure.
My EVAP system needed a new solenoid valve and gas cap so I want to check all the important gas metered valves in the engine. As I understand the system, my pcm only adjusts fuel metering based on engine bank performance and not each engine cylinder performance so I want to make sure I do not have an out of bounds injector after ten years of use.
If I fire each injector only once with 50 pulses I assume I can then start the vehicle without a problem. Is that correct or is it mandatory to take the plugs out to remove the fuel?
It adjusts fuel trims by bank but its pretty good at seeing issues. If it had to adjust the pulsewidth on all of one bank’s injectors because one was screwing things up, pretty fast it would see A/F ratios reacting wrong or a misfire and would know something is up. That in turn would generate codes. Then again, feel free to get some experience with it and do some testing.
If you fire off the injectors at 50 pulses, hold the gas to the floor and crank the engine between each cylinder tested. That way you give it a chance to run and not have all your cylinders puddled up with gas. Flooring the engine puts the PCM into clear flood mode, and it will not fire the injectors during cranking to allow you to clear a flooded engine.
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