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Zmigraine

78' 280z EFI troubles

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I'm currently dealing with not having power at any of my injectors. 

I've been using the 78' FSM to help me diagnose this issue. To support the findings I tested for continuity on the 35 pin connector based on the prescribed tests in the FSM.

There was really nothing of note besides not having power after the 10 pin (powerline circuit). 

I'm starting to wonder if there's a ground that's missing. All of the grounding points in the engine bay check out though. as far as i know, I have spark (running a GM hei instead of  the TIU), I have been running the original style fuel pump but have an aftermarket one as well. 

All my fusible links have been replaced with Maxifuse blocks. 

My relays seem to be in good working order ( does anyone know if Nissan still sell the replacement ignition relay)

The car will start on starter fluid but i did notice that the tach does not move at all. 

 

Background: 

I have two 280's, one black and one white. The black one was the donor vehicle as i deemed the rust situation and previous fender bender to be more than i cared for. It was an automatic. At the time we got its engine to run while up on stands. The other is white with a 5speed. I assume it was a swap due to not having a 5speed badge. This car was saved from a local scrap yard along with some choice parts out of a green all original 76 that had seen better days. 

We swapped the engine from the donor vehicle to the white one and it no longer seems to want to work. fuel wise anyway.

 

Any thoughts and suggestions will be appreciated.

 

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EFI Jumpers.jpg

So, if you're concerned about grounds, check for continuity from wire 74 to ground. You'll find this wire at the EFI relay. It should be on one of the middle pins on the 6 wire connector. 

The coil on the EFI relay is energized off the white/black wire from the ignition relay (make sure the ignition relay is good).

For testing, you could put jumpers on the engine harness at the EFI relay as I have shown in red. For safety, keep the fusible link unplugged until you are ready to test.

As for the tachometer, depending upon how you (or the PO) wired in the HEI to replace the TIU, you may have removed the trigger signal for the tach.

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So I took some time to do some research. Put in my best ignition relay(the stock one in good condition) and even bought a new injector or two. That’s all beside my main point though. 

I switched to a different efi relay to check to see if there would be any changes. The results are as follows. Out of 12.56 volts across multiple electrical points in the car, the power to the injectors sits at .62 across the board. It spikes to .67 when the car is cranking but that’s it. 

Is this a sign of a burnt out efi coil? I’ve gone from nothing to very little voltage so I’ve gotten somewhere at least. 

Also, is there a diagram showing the FI fusible link connection to the battery? There has been multiple hands in the pot here, most of which like electronics less than myself. I’m starting to wonder if that fusible link should come from the positive or negative. 

7D608D04-94E3-45E0-918A-F371A3F48ED9.jpeg

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Why would you put the fusible link between the circuit and ground?

Now go back and check post #2.

Go to Blue's collection of tech tips for the wiring diagram or search here for a color copy of the wiring diagram.

Edited by SteveJ

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2 hours ago, Zmigraine said:

Out of 12.56 volts across multiple electrical points in the car, the power to the injectors sits at .62 across the board. It spikes to .67 when the car is cranking but that’s it. 

I think that you might be measuring power at the injectors incorrectly.  Looks like you're probing across the pins in each connector instead of from a single  pin to a ground point.

The fact that your tach doesn't move and it starts with fluid implies that the Pin 1 circuit from the coil to the ECU is broken.  Check Pin 1 continuity to the coil 

Or you have a funky ignition system like a an MSD or Crane.  They don't work well with the 280Z EFI.

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Just to make sure, did you check the EFI connection by the battery?  It splits off the positive terminal.  That connection can get overlooked connection wise and or become corroded.  There is also a fusible like there that you could check.  top picture, upper right hand corner.

Edited by gwri8
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