Electrical Problems 78 280z

[tleverett]

Ok when my ignition switches to ACC absolutely nothing happens, no lights on the dash, no warning sounds no nothing.The ignition will work in the start position and will crank the starter. I started the car with starter fluid in the intake but would not run, it was only for a second. I bought a new ignition switch after checking the continuity of the different positions and one portion was out.  The fuel pump is not pumping gas into the motor to keep it running I believe. I wired the battery to the fuel pump and it did push gas through to the motor so the pump itself works. When I started the car for that second the tachometer did nothing, it actually looks like it is just sitting on 1k not moving(maybe its stuck/broken) The only gauge that for sure works is the volt meter.  Does anyone know why the ACC mode may not work (not the ignition switch) and if that may be linked to the fuel pump not running (maybe the ecu)? Also I checked all the fuses and relays on the passenger kick panel, also all the relays by the fusible links. Also changed all the fusible links to the maxi fuses and they are all good.

[jonbill]

I don't think the fuel pump is meant to run on acc. Acc is for accessory, like the radio.
"On" is where fuel pump and the ignition get powered.
Based on my 74 260, I wait to be corrected!

[tleverett]

@jonbill you are correct, the fuel pump does not start until turned to the start placement. However I just wasnt sure if there could be a correlation between the ACC mode not doing anything, and the start mode not running the fuel pump. I'm hoping there might be one thing that helps control both, besides the ignition switch. I know the switch is good. 

[jonbill]

I think it might be correct that the fuel pump only runs on "start". There may be an oil pressure switch that means the pump only runs when "on" if the engine is spinning.

[SteveJ]

Look at this thread. I describe the operation of the fuel pump relays for the 78. https://www.classiczcars.com/forums/topic/62552-78-280z-turns-off-with-turn-signalreverse-lights

 

The interesting thing about the linked thread is the time it took to resolve because the problem was upstream (corrosion at a factory splice) from where the OP and I thought the problem resided.

Basically, here is what you need to do.

1. Verify that you have good connections between your battery and all of the fusible links.
2. Verify you have the proper functionality at the relays.
3. Verify the proper functionality of the oil pressure switch.
4. Verify the proper functionality of the ignition relay.

The most important thing is that you need to be able to use a multimeter well. If you don't, find someone who does. You'll also need the wiring diagram. @wal280z has created a color version of the 78 diagram. He may be able to tell you where he posted it. It may also be available in the downloads section of this site. I have a link to the downloads section in my signature (visible if you are on a computer).

[tleverett]

@SteveJ Holy crap that's funny, I've read select pages from that when I was trying to diagnose the ignition switch problem but as I was looking for different information I didn't read through the whole thing til now. 

Please bear with me on this because I am definitely trying to learn all this stuff, and I greatly appreciate all the help. My dad said he would help me restore a car, but when the car I got wasn't american muscle he didn't really keep interested. Also my friends don't know anything so I haven't been able to bounce ideas off anyone. 

I'm gonna share some more info about what I've done and we can go from there. Also keep in mind all testing basically needs to be able to be done solo, because I work on it by myself. 

I did the fusible link upgrade from http://www.atlanticz.ca/zclub/techtips/fusiblelinks/index.html. The 4 w/r wires to the fuses on one side, a 4ga wire to the starter on the other. I cut back the w/b wires a little and are not connected to anything currently. I saw on the link below, there is one fusible link that goes to headlights only, i believe I saw wires that are spliced in to headlights (the wires run to the headlight area) so maybe there is a fusible link problem I didn't realize since I replaced them, but might be the crimps below the links. 

 

The  best place to check the voltage would be at harness c9  where all the fusible link wires are connected correct? I'm not exactly sure where it is yet, but I just want to have a decent idea of what I'm doing before I get to the car. 

I will take all the fuel relays (maybe the ignition relay too) and battery home where my FSM is, pick up some alligator clips is so i can test them one at a time to make sure they work correctly. 

Once I've done the relays, Ill test the oil pressure switch. Just to confirm, it's right next to the oil filter with the 2 wired plug correct? 

I know the pump wiring goes from the pump to the harness (splits off one part to the ecu I believe) to the relays and has a cutoff on the oil pressure switch and the alternator. I sprayed the relays, oil pressure switch and alternator switch with cleaner and plugged in and out multiple times. 

 

[wal280z]

10 hours ago, SteveJ said:

You'll also need the wiring diagram. @wal280z has created a color version of the 78 diagram. He may be able to tell you where he posted it. It may also be available in the downloads section of this site. I have a link to the downloads section in my signature (visible if you are on a computer).

Appreciate the kudos @SteveJ, but I didn't do the '78 version.. Only the '77 is what I can take credit for.

I believe the 1978 version is courtesy of @awolfe, I found this thread >>

 but I believe @Captain Obvious was kind enough to post that to the download section.

[wal280z]

2 hours ago, tleverett said:

I did the fusible link upgrade from http://www.atlanticz.ca/zclub/techtips/fusiblelinks/index.html. The 4 w/r wires to the fuses on one side, a 4ga wire to the starter on the other. I cut back the w/b wires a little and are not connected to anything currently. I saw on the link below, there is one fusible link that goes to headlights only, i believe I saw wires that are spliced in to headlights (the wires run to the headlight area) so maybe there is a fusible link problem I didn't realize since I replaced them, but might be the crimps below the links. 

 

@tleverett(Emphasis in bold)

That's the way I wired my headlight relay power source. It is not the way the factory wired it. Please don't mistake my modification to the way it should be wired.

[tleverett]

@wal280z no sorry, i was referencing a splice the PO put into the car to what I think could possibly be to bypass the fusible links? No idea yet. One step at a time, I'm just trying to get this baby to run lol and ignition/fuel is more important than the headlights currently.

[wal280z]

4 minutes ago, tleverett said:

@wal280z no sorry, i was referencing a splice the PO put into the car to what I think could possibly be to bypass the fusible links? No idea yet. One step at a time, I'm just trying to get this baby to run lol and ignition/fuel is more important than the headlights currently.

Gotcha. Best to follow @SteveJ advice in post #5. If your fusible link upgrade didn't address any of the factory splices at the 'T' in the harness directly below the original fusible link location, that should remain suspect until verified that all connections are good.

Note, when you connect the fuses on your upgrade, and you still don't have power as described - give the 'T' portion of the harness a slight twist. If you hear relays clicking, that's part of your problem.

As far as the other gauges - you can check the fuel gauge operation by grounding the yellow wire on the connector that connects to the sending unit connector. (I don't have a 78 FSM, but on the '77, it is shown in detail 'a' on pg BE-94 (dash harness wiring layout).

[tleverett]

@SteveJ @wal280z

okay i peeled off enough harness tape to find the 2 splices and honestly not too bad. I checked the voltage at the harness c9 and all four fusable link wires have voltage (small victory, maxi fuses worked correctly). Okay then i was taking off the ignition relay and all of a sudden THE ACC SOUNDS STARTED GOING OFF, but then turned off. I was pretty excited. i kept unplugging/plugging the relay and every once in a while the ACC sound would come on. I tried to start the car but the oltage was dieing on the battery. I didnt hear anyhtring from the fuel pump the whole time however. I also checked the voltage to the t post on the alternator and it had it. The other w/r wire going to the alternator also had voltage. 

I am going to test all the relays in a little, however it seems for now I do need an ignition relay if not now soon since it is working intermittently. Any ideas where to go for that?

 

I will work on the oil pressure check tomorrow. 

[tleverett]

Fuel pump relay. 90-91 did not have continuity in normal condition. 93-92 had continuity when +/- was added to 90-91
Fuel pump control relay under normal 95-91 yes. 95-94 no.

So it appears all 3 relays are bad. Fml any idea where is best to get them?