Nissan Repair: No fuel pressure, oil pressure switch, 1991 nissan stanza

Question
QUESTION: Electrical problem
1991 Nissan Stanza 4 cyl Front Wheel Drive Manual 200000 miles

With the key "on" I have 12 volts and correct fuel pressure from the fuel pump. Once I start cranking the engine the voltage drops to around 8 volts and I have no fuel pressure. I have replaced the fuel filter, fuel pump, fuel pressure regulator, fuel pump relay, and oil pressure switch. After all this a began to trace the voltage drop starting at the fuel pump all the way up to the fuel pump relay then to the connection on the firewall and still have a voltage drop. According to the schematic (if I am reading it correctly) from the firewall connection (left rear of the engine compartment) it then goes to the ignition switch. Could the problem be in the ignition switch? The engine cranks but will not fire up. I have fire at the plugs and the timing chain appears to be okay. Any suggestions? Thank you!

ANSWER: Ted,

The ECM provides signal to cut ground to the fuel pump relay.  If you have a faulty ignition switch you could wire the fuel pump relay to a switched ignition source to see if you get fuel pressure.  If so, and I think you will, this would solve the problem.  Otherwise you could try replacement of the ignition switch.  You have replaced all the parts that should be associated with the fuel pump less the ignition switch and ECM.  Now, one last thing and I have seen it before.  If the oil gallery that feeds the oil pressure switch gets plugged, even partially, it can cause the ECM to unground the fuel pump relay.  Remember that the oil pressure switch is the fail safe for when the car gets into a crash or the oil pressure drops on the engine, keeping it from hurting the engine or keeping you safe if the car turns over and the fuel pump were to continue to pump fuel.  Now, you could just rob an impact switch off a Ford and use that as the safety feature and just wire around the problem.

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QUESTION: Von, thank you so much for the quick response! I believe I will try to replace the ignition switch next. Any tips for this job or is it straight forward?

Answer
Tedd,

The ignition switch is held in with a couple of anti-tamper bolts that you need to drill out to get off.  You can install a factory nissan switch that comes with the bolts or you can get a couple of bolts to thread in with an aftermarket switch.  Your choice and I prefer the last option as cheaper.  Do check the circuits to make sure where the power drops off and then you can do as you please.  There are options.  A wrecking yard and the Ford, Land Rover impact switch is the cheapest.  You find it in the trunk of a Ford or under the hood of a Land Rover/Range Rover.