Been having a problem with a cylinder not firing in my 98' Nissan 240sx. First thing I checked was spark, which was all good. I know compression is fine in that cylinder, and the plug was dry when I pulled it so I know fuel is the problem. Checked/swapped injectors and found that wasn't the problem. I found very low voltage at the injector plug so we ripped into the harness and found a small short in the 12v wire to the injector. Fixed that and now the voltage is fine. However, the injector is still not receiving a ground signal from the ecu. We tested continuity in the ground wire all the way to the ecm harness connector and it was fine. I have a second ecu for the car so we swapped that in which changed nothing as well, which rules out an ecu problem.

The only thing left I can think of is the Cam position sensor not working correctly. We tested contiunity in all the wiring for the sensor following the fsm instructions and found on problems. Now I need to know if there's any way to check if the cmps (cas) is actually sending the correct signals or not.

Could a faulty cam position sensor cause only one cylinder to misfire/not fire? I really have no clue what else the problem could be. This problem has been real intermittent which made me think it was originally a wiring problem, but we've tested pretty much every connection possible and they're all fine.

You can look at the signal's waveform with an oscilloscope. There could be a bent fin or something causing a bad signal for the cylinder at fault.

i have never seen a Nissan not fire on one cylinder with a faulty cam sensor,if the sensor is bad it will not fire at all.
unfortunatly with out looking at the car i can't give you an idea where else to look but i know that when the cam sensor is bad they Nissan will not start.

I wouldn't expect you to have spark on that cylider if you had a bad CMP sensor signal. If I were in your position, I'd check the signal to the injector either with an oscilloscope or with a noid light. You say it's not receiving a ground signal. How did you attempt to measure that? Did you duplicate your setup on another injector that is working fine to make sure your test aparatus was good?

-Rod

The CPS on a Nissan just tells the ECU where TDC is (I thought).

I would try a known good ECU. Its possible the relay for that injector is bad in the ECU.

The CPS on a Nissan just tells the ECU where TDC is (I thought).
I would think that might be the only purpose of the Crankshaft Position Sensor. I would expect the Cam sensor to determine when to fire the coil.

On this car, is the Cam sensor integrated into the distributor?

-Rod