1992 240sx dohc with automatic will not crank.

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Since my car won't crank how can I tell if the computer is turning the injectors on? It seems to not be getting fuel but there is plenty of pressure being delivered to the injectors. The car has good spark and the knock sensor, maf & TPS all ohm out within specs of the book. (TPS gets proper voltage from idle to WOT). The car ran great but had intermittent problem. It will decide to quit at times. The last time it quit I took it to Nissan mechanic. He replaced the temp sensor in the intake and it ran fine for 2 weeks then quit again and now won't crank. It turns over fine and sounds like it wants to crank but won't. I'm wondering if there is a problem with the ECM or wiring. Any ideas? Any way to probe a certain wire at the ecm to see if it's sending a signal to injectors? When it did run the injectors ticked and they also ohm out to specs.Thanks,Zoom

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If I pull the return line off it will send fuel through the return line when I turn the key on. When I try to start it I don't see any fuel coming out the return. Is that normal or should it always have fuel going out the return? Zoom