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Topic: injector balance test (Read 1958 times) previous topic - next topic

injector balance test

Injector balance test
I read up on this and it caught my eye
you might want to disconect your Idle control motor assy prior to this test
warm up your car
shut down car and uplug ISC motor
start engine
unplug one injector at a time
observe a TAC mounted somewhere that you have as stock or prefab'd
there should be no less than 100 rpm of drop for any injector.

Re: injector balance test

Reply #1 –
Actually, EEC-IV has a built-in cylinder balance check. I remember a teacher doing it as a demonstration on my '87 Sport as part of a course
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Re: injector balance test

Reply #2 –
Quote from: Thunder Chicken
Actually, EEC-IV has a built-in cylinder balance check. I remember a teacher doing it as a demonstration on my '87 Sport as part of a course


Actually only the SEFI EEC-IV has the built in cylinder ballance test... The CFI and batch(bank) fire, do not have this feature....

Re: injector balance test

Reply #3 –
guys,,
my engine/emissions diagnosis manual mentioned the sefi balance test as well.  it got really confussing because of all the years covered.  the only accurate info i could come up with was the one thing these procedures had in common.  each engine type called out to remove the injector conn one by one. 

No where in the manual does it say to unhook the idle control motor.  I only pointed that out because the manual implied that the ISC would instantly try to compensate.
since i know that the CFI car "will" run without the ISC hooked up, i thought it would be a good idea to unhook it so your tac does not go wacky.

Will the multi port engines with the isc mounted in the upper intake run if the isc is unhooked?

Re: injector balance test

Reply #4 –
Quote from: jcassity
Will the multi port engines with the isc mounted in the upper intake run if the isc is unhooked?


Yea as long the base idle is not too low...

But it is not necessary to do so on a SEFI cyl balance test. When the test is activated the EEC locks the IAC so rpm is constant, then measures the rpm drop as each injector is shut off. Roughly the sequence is stable the idle, shut down first injector for approx 5 seconds, restablize idle and move on to next inj. etc. Any cylinder that does not have at least a 75-100 RPM(may not be actual figure, I'm guessing) drop is considered weak. In actuallity it would be a good test to locate anything from a burned valve to a dirty injector or even bad spark plug, wire or dist cap......

Re: injector balance test

Reply #5 –
the one thing that came to mind when i was reading this info is the upper intake blocks off half your injectors on the pass side.  thats gotta be a downside to doing this test and it being easy or not.