I'm currently diagnosing my 1977 280Z. In the "ACC" position, I have dash lights and a few relay clicks. In the "ON" position, I have no dash lights. no activity change. In the "START" position, the engine cranks over, but does not start. I've removed the fuel lines and I have no fuel pump actions during the starting position. No fuel pump action period...

Here is a link to the manual that I'm currently using so that we can be on the same page: http://www.4moores.com/280z/files/280zfuelinjectionbook.pdf

On page 33 it tells me if the relay clicks (which it does) that I should go to page 62, then page 61.

So on page 62 and 61: I have full source voltage at pin 1 while in the "ON" position. While looking at pin 10, I only have .6 V.

Now the funky part, is that I am testing the same two pins while in the "ACC" position and I see the numbers flip. Pin 10 is seeing the 12 V it is supposed to, and pin 1 only has 1 V.

Is it possible that my ignition switch is messed up? I read the factory service manual as telling me that the fusible link is supposed to provide power through the fuel pump relay while in the "ON" position.

I have replaced the fuel pump relay with a brand new OEM part from my Nissan dealer. This has not remedied the issue. Also, all fusible links appear to be in proper condition. (Confirmed using a Fluke Digital Multimeter.) All electrical parts are OEM as far as I know (other than an internally regulated alternator being installed). The previous owner let me know that his fuel pump died and he replaced it. 6 weeks later, it would not start one morning. I replaced the relay because it tested bad as per the FSM.

The vehicle is currently sitting in my garage taking up space that my roommate could be using to park in (it's <30 degrees outside) so I'd really to fix this ASAP.

I would suspect the switch on the back of the ignition where the harness plugs in.

I am interrupting to clarify that the document in your link is most commonly referred to as the fuel injection "bible", which is different than the FSM (factory service manual).

Anything specific? Or simply corrosion or a loose wire? I'm going to check now. BRB.

Yes. The Bible. I'm sorry. . My fault.

The contacts can go bad inside the switch. If so, it has to be replaced. This diagram shows where continuity should be:

So the ignition switch seems to be okay. Still have dash lights on "ACC" and no dash lights in "ON" position. Still have 12V in "ACC" and 0V in "ON" as monitored at pin 10 the large 35 pin ECU connector.

All of the wires underneath of the dash leading from the ignition switch to the firewall seem to be okay. No obvious nicks or cuts that could be allowing the voltage to jump from one wire to the other.

I just checked the fuel pump/main relay and all is OKAY according to the FSM.

Edited December 16, 201113 yr by Inthenameofweez

Any ideas on a way to bypass the circuitry to determine what wires might be okay and what wires might be effed?

I'm gonna go power up the fuel pump with my 14.4V drill battery. If the pump proves okay, I can memorize the sound and confirm wiring/ECU. Again, the relay and ignition switch is okay. However, I'm still seeing conflicting voltages at the 35 pin connector. Pin 10 sees voltage in "ACC" and nothing in "ON" like it should...

Do you have spark?

If you have an early77 then the vane switch in the AFM should be checked as it enable/disables the fuel pump.

Yes!! Spark has been confirmed. I can get it to start with starting fluid.

I tried to play with the AFM. How far do I need to push it up? I'll continue playing with it, but I'm not getting the 12V to the ECU (PIN 10) as the Bible tells me I should be. ("ON" position)

Am I focusing on the wrong issue? Looking at the schematic, it seems that the Air Regulator could also prevent the pump from running. Do I read that wrong?

Disconnect the small wire at the starter solenoid, the one that pulls right off, and turn the key to Start. The fuel pump safety circuits are bypassed at Start and you should hear the fuel pump run. If you have a fuel pressure gauge you can measure pressure this way also. It should be ~36 psi.

What month 77?(on driver door pillar plate)

How many wires to oil pump sensor (next to oil filter). 1 or 2

Sooooooooo, I just checked for fuel pump action with a drill battery and nothing. Not even a squeak. So I've got a bad fuel pump for some reason. Hoping there isn't junk in the tank clogging it. So while I'm under there, I checked for the command under the "START" position. And guess what? I've got 12V heading to the fuel pump... This was all with the starting solenoid disconnected. I'm hoping that means that my previous worries about the ECU/RELAY/IGNITION SWITCH are false concerns. If I can get the pump to turn on during "START", then it should at least sputter and fire a bit, right?

This 280 was built 2/77 and there is only 1 wire coming out of the pressure sender.

I'm gonna go see if the pump on my parts car runs with voltage applied... BRB.