Ford Repair: Not firing injectors, meg ohms, ac volts

Question
QUESTION: Hi, Im stumped.. I have an 89 F150 5.0, and batch 1 injectors(1,4,5,8) are not firing.  I have tested all but #4 and they test within specs.  The inj. harnesses all show 12v with key on.. TFI module tests ok, PIP gives me AC volts with in spec, all other sensors test ok.. Am I missing something without replacing PCM? Reference voltage from PCM to all sensors is about 4.5.. Thanks for any help

ANSWER: How are you determining that the injectors are not firing? e.g. if you have some sort of voltage at the injector, what kind of test tells you it is not opening?

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QUESTION: An automotive stethascope to the inj. body, indicates no sound, compared to the other batch.  Also if I take off the harnesses while it is running does nothing.. I forgot to mention that no check engine light is on, and if i pull codes all I get is 11(system pass) and 33 EGR function not detected.  EGR should have nothing to do with it because its basically a highway function only.

Answer
Swap known working injectors for the one(s) that seem to not be working. If you get the same symptoms then the problem is electrical and not the injectors. If you have checked all other possibilities, you have to consider the EEC. Make sure the electrical tester has an input impedance of 10 meg ohms or greater. If not, you may have damaged the EEC output circuit.