1977 Injection relay question with picture

[MEZZZ]

I still have not been able to get my car started and downloaded and printed out the fuel injection manual Saturday in hopes of narrowing down the problem.

I had my brother over yesterday and we were talking and he decided to look at my car and read over the manual. I had told him how a few months ago I had been under the dash and unplugged the relay harness. A week later when I tried to start the car it wouldnt start, then I remembered I had unplugged the relay. He asked while looking at it "Did you maybe not plug it back the same way". He looked and told me while he was under the dash, the plugs are the same and depending on which way you turn them, they can go either top or bottom. He swapped them around and told me they fit either way, now I cannot remember what order they were in.

I did a search of the F.I. Manual as well as the F.S.M. and they only show a drawing and do not mention which plug goes where, only one is the power relay and one is the fuel pump relay. From the diagram, it appears the fuel pump relay is the top. I just dont know if the black or white plug is the correct one. Can anyone tell me if the black plug goes on the top or bottom of the relay?

Also, when ripping out the old carpeting, I found a peice of speaker wire that was coming from the general vicinity of the relay bracket. It was wire nutted and just laying in the driver side tool box of the car. At the time I figured it was a speaker wire that a P.O. had done in the past ans someone just left it laying in there. Upon looking yesterday at the relay, we traced the wire up to the wires coming out of the ECU harness. If you look at the photo, you will notice a wire with electrical tape running in front of the ECU and up into the harness. Now I am perplexed as to what this may have been. My first guess was a wire running back to the fuel pump, but it is on the driver side of the car. I left it hanging out of the car with the intent of taking it out and rolled my car out of the garage and inadvertantly over the wire. It tore right where it was coming out of the door. I am thinking maybe I pulled something out of whack in the harness and maybe thats why it wont start now.

If I had swapped the relay positions when I plugged it in last winter, could I have caused damage to the relay perhaps? Maybe the ECU? The car did start last winter after plugging it in.

Any help, as always, is appreciated. Sorry for the long post.

[MEZZZ]

I just got back from the garage (my wife and daughter went shopping ) and decided to try to figure it out myself. I took the plugs off the relay and looked at them, one had one more wire on it than the other, 5 vs. 6. I then looked at the number of connections on each relay and figured out that the black plug should be at the bottom of the unit, opposite of what the photo shows and what my brother did in swapping them.

I carefully matched them up with the relay, plugged them in, cranked the car and...nothing!

I pulled out the injection manual and did the first step which is pulling the lead off the solenoid and turnng the key to start in an attempt to hear the fuel pump and pressure regulator. That test was successful, I heard the fuel pump turn on and the prssure regualto kinda pssstttt sound. I have a brand new regulator and the old one was not clamped going into the intake at all, so I clamped the injection hose down when I installed it.

Thats as far as I got with the exception of trying to turn the key to on and then start while placing my hand over the power relay and felling for a "click". I fell a little something when I cranked the car, not sure if I would call it a click it not as I feel the same thing on both plugs.

Tomorrow is another day.

[sblake01]

Strange thing about the 1977 FSM. Were you able to find that relay in the wiring diagram? I couldn't. The 77 FSM shows the same setup as the 78 FSM which has two seperate relays instead of the one combined one and they're under the hood in the relay box. So I looked at the 75 and 76 FSMs and they showed the relay in your picture but with different color wires on the plugs. Hopefully someone who has a 77 will chime in here. As far as that other wire, I don't have an idea what it could be as, like I said, 78s are set up a little differently. What color is that wire?

[MEZZZ]

Stephen,

Thanks for the reply. I opened up the FSM and it is entitled 77_datsun_280z.pdf.

I found the photo and cut and pasted it into here. I found it in page EF-14

The wire with the electrical tape wrapped around it? It is speaker wire, or so it appears. Clear insulation on both sides. It was wire capped at the end, sitting in the driver side tool box, just laying there. I have not yet unwrapped the tape to see where it is attached but it is obviously spliced into the harness coming from the ECU.

I am bound and determined to figure this thing out! According to the F.I. manual, my next step is to pull the lead ignition wire and check with a test light, then go on from there checking the ecu harness and the various pins.

One thing I did check yesterday which makes no sense. First, with both black and white connectors off, I still could start with starter fluid. My brother just wanted to try for the heck of it and it did fire momentarily. Then, with the connectors plugged back into the relays, I took a multi meter, with the key on, and checked for power at one of my injectors. I got nothing.

So after I plugged the connectors into what I think is the correct way, black plug on bottom, I turned on the key, checked for power at the #6 injector and still nothing.

Shouldnt I get something with the key on? I have fuel in the rail to be sure, spark at the plugs. I have to since it fires momentarily using starter fluid, I am not getting anything at the injectors. Keep in mind, I am only beginning my learning here, so any advice is more than welcome.

[sblake01]

Yeah, I've seen that. Like I said, I have all of the 280Z FSMs. What I was referring to is the fact that it doesn't show up in the wiring diagram in the 77 FSM.

[sblake01]

Maybe this diagram will help. It's better than the one in the FSM though the colors on the relay plugs are different from yours.

1977 280Z Color Wiring Diagram

[MEZZZ]

Maybe this diagram will help. It's better than the one in the FSM though the colors on the relay plugs are different from yours.

1977 280Z Color Wiring Diagram

, I was just looking at the same thing, I had the wiring diagram saved in a couple places on my hard drive. You are right, I am by far an expert at reading wiring diagrams, but I see no blue wires, just green, red and black. Thanks for taking the time to send it though. Since you helped me discover I have a P79 head on my car, I am now wondering if maybe they changed out other things as well? Maybe the harness or ECU? I did look at my AFM and it does have a 7 pin connector on it. I am going to have to bite the bullet and check step by step through the FI manuals troubleshooting steps.

Can you tell me this much Stephen, should I have power at the injectors with the key in the on position?

Thanks...