I believe the success rate here is pretty good with the past history mentioned in earlier posts presented. What puzzles me is the cost of the relay. I’m sure there are folks here on the forum including myself have a factory one available since I converted to OER Carbs.

Welp, Im official stuck. I'm having a difficult time trying to get through this relay.

Im following this troubleshooting guide and Im suppose to get power to pin 4 of the ecu harness but no such luck.

Wire 70 (relay pin 88z) traces to the positive side of the battery and has good continuity.

Wire 43 (relay pin 88b) traces to the negative side of the battery and has good continuity.

Using the power probe, I can confirm that the fuel pump works and has good continuity,

Two other pins run to a relay (one in front and one in back) I can hear clicking.

Messing around with the power probe on the new relay will activate the relay circuits. (while not attached to the harness)

I believe part of my problem may be at the ignition switch. According to the diagram at the top, Wire 76 (relay pin 86a) runs to the start side of the ignition switch, It doesnt matter what position the key is at, I dont receive any power to the circuit. If I use my power probe to simulate I still get nothing on the circuit. Ideally, I should be able to hear the fuel pump prime and/or the new relay click.

I should note that the ignition switch doesnt lock the steering wheel and it also allows me to pull the key out in any position. It does work to turn over the car just fine.

Looking at the diagram I see a fusible link between the battery and the ignition switch. I need to check that. Even so, the power probe should make the circuit work?

On the relay pins 4/47 and 76 (86 and 86a) are the positive for the relay coil circled below. At that point, the WR wire coming to pin 73 (88y) should be connected to pins 48 and 74 (88C & 88d).

So here's what I suggest.

1. Check for continuity between terminals 86 and 86a.

2. With the relay plugged in, check for voltage to ground at 86 with the key in start. (You can save wear and tear on the starter by unplugging the black/yellow wire at the solenoid before doing the test.)

3. Check voltage to ground at the ECU harness on pin 4 with the key in start.

Good News! The problem was not reading the fine print. To get the voltage to display properly, I had to actually try and 'start' the car. Not just leave it in the on positiion. I was expecting to at least hear the pump prime at the 'on' position but it doesnt want to do that.

Thank you @SteveJ this whole sentence was clear enough to understand what I needed to do. Disconnection of the starter wire was part of the diagnostics but its on a different page then what I posted. Even so, having you mention it helped me follow through with the process.

"With the relay plugged in, check for voltage to ground at 86 with the key in start. (You can save wear and tear on the starter by unplugging the black/yellow wire at the solenoid before doing the test.)"

Sometimes just hearing something stated in different terms makes all the difference.

So, even though Im not hearing the pump prime, I am getting fuel to the front of the car. I hooked up the lines and tried again, but turns out i didnt have the ignition module hooked up, I had that part taken apart and waiting on some wiring terminals to make it pretty. I think I also had the fuel lines on backwards and when I disconnected, it sprayed quite a bit over everything so I decided to call it quits and let it flash off.

The fuel pump doesn't prime in the early EFI. I don't think that came until the ECCS system of the 280ZX Turbo. In the 280Z the AFM has a switch that "senses" air flow and enables the fuel pump - no air flow, no pump, so the engine has to be making vacuum and sucking air through the AFM. Safely First.

On 12/27/2025 at 2:02 PM, nowak1981 said:

...

So, even though Im not hearing the pump prime, I am getting fuel to the front of the car.

Have you installed a fuel pressure gauge between the filter and fuel rail on the engine itself? You will need that for diagnostics down the road and be able to see what is actually occurring. Quite a few threads here on that. Definitely a must do IMO. So many folks have been down this road.

1 hour ago, Yarb said:

Have you installed a fuel pressure gauge between the filter and fuel rail on the engine itself? You will need that for diagnostics down the road and be able to see what is actually occurring. Quite a few threads here on that. Definitely a must do IMO. So many folks have been down this road.

I havent, I have one though. i need to read the book and figure out which one is supply and which is return. I wasnt paying attention when I took it apart

On 12/27/2025 at 1:02 PM, nowak1981 said:

I think I also had the fuel lines on backwards and when I disconnected, it sprayed quite a bit over everything

The lines are pressurized with the lines connected correctly. So the spraying would be normal.

The hose that connects to the fuel pressure regulator is the return line. The supply line connects directly to the rail.

The upper steel line coming out of the filter is the pressure side. Take pics of anything and everything before you consider taking it apart. Ask me how I know. Tons of pics on the internet. By the way do you have an FSM for your make and model? If not that’s thats the way to move forward before changing anything IMO.

Yea, I do have the fsm as well as 3 other manuals. I was getting excited with solving the fuel relay issue.

Finally got all the parts and tools in that I needed "wanted" to get the job done.

The heatsink that I got doesnt bolt up to the module I have, so I had to drill and tap new holes. Also used a rivnut in the fender to have something to bolt it to. Its not as clean as I would like, but it was a fun exercise.

Created a nice clean looking harness and topped it off with cap head screws. Also used some computer thermal paste to make a good connection to the heatsink.

Finished producted mounted.

I also fixed up the couple exposed wires I found and put new terminals on.

Im messing around on the forum and its always been in the back of my mind that this may not be the original engine. So I did some digging, evidently Wikipedia was able to shed some light on the engine and this is what I found

This is what is stamped on the side of my engine.

As far as I can tell, none of those vehicles were in the US market. So where the hell did this come from? Looks like it produces a little bit less horsepower than an l28e =( This engine is paired with an N47 Head, but I cant find any info that this head came from the factory with this engine. Strange.