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Usain_Boat

78 280z turns off with turn signal/reverse lights

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So the electrical saga continues with my z...

I have a 1978 280z and it recently developed a tendency to turn itself off when I'm driving. It started with it just turning off when shifting into reverse but has evolved into turning off with the right blinker once (I could hear the a relay in the passenger foot well clicking on and off with the blinker) and also just randomly while driving. Today it died in my neighborhood before i could leave and wouldn't turn back on until I jiggled the main wiring harness around. Because of all of this I suspect two wires shorted together since the turn signals and reverse are on the same circuit and removing the fuse for them fixes the problem but if someone could help me track down where in the harness i should be looking and what wire to the main ignition relay or other relay that would kill the car might cause this.

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2 hours ago, 240260280 said:

Probably wires in steering column that connect to the ignition key assembly.

I'll check there but the turning off when going into reverse has me thinking it would be over where those wires run

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With the behavior you described, it's likely one of two scenarios.

  1. There is a problem, possibly with the ignition switch, and what you perceive as triggering events are just coincidence.
  2. A previous owner has hacked into the wiring to "fix" problems.

You might want to pull off the steering column cover and start looking for splices.

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I fixed a splice I didn't like on the ignition wire and I checked and have power to the coil (last thing on the ignition wire I think?). The car still won't start though. I have no dash lights like the parking brake light and my fuel pump won't turn on.

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Let me be frank here...Frank Drebin.jpg

You'll need to supply a LOT more information to get decent responses (and not have someone posting pictures from The Naked Gun).

You found a splice you didn't like, but you don't say what wire was spliced (the colors are important), how it was spliced, or where the foreign wire went to. That splice may have been one of those "fixes" a previous owner did to work around a problem instead of diagnosing it properly. 

It is challenging to track the history of the issues. When did each issue start? You added things about the dash light and fuel pump. When did you remove the splice?

We cannot see your car, so you have to paint a picture with words (and post photos). If you have a half decent camera on your cell phone, there's no excuse for posting without photos.

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Could it be loss of ground? He has power at the coil but it's an efi car.

Does the starter spin the engine? ie Turnover?

Does it fire at all when it spins?

Will it fire if you shoot starter fluid into it?

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Sorry for not providing info but the splice was on the black with white stripe (the ignition wire). The splice was my fault from installing a relay for a light I only wanted on with ignition so it went to a switch that currently does nothing. I spliced it with a waterproof heat shrink crimp but it was loose and I was able to pull one of the wire off. Again my fault. I then soldered the wires back together and covered them with heatshrink this morning. The issue of the dash lights and fuel pump not work has been with the car ever since I put it back together after rust and paint work. This is my first run with redoing a car so I didn't pull the wiring harness before it went to the shop that did the aforementioned rust and paint work which I regret. I will post pictures when I get home.

 

If there is anything else I should/can provide just let me know.

Edited by Usain_Boat

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50 minutes ago, Patcon said:

Could it be loss of ground? He has power at the coil but it's an efi car.

Does the starter spin the engine? ie Turnover?

Does it fire at all when it spins?

Will it fire if you shoot starter fluid into it?

The starter spins but the engine doesn't fire at all when it is turning over. I haven't checked with starter fluid but with the wire pulled off the starter solenoid I do not hear the fuel pump so I will check for spark and starter fluid this evening.

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Mind you that I'm probably not the first one to come to with electrical issues, but back to what @SteveJ mentioned, did you check your ignition switch?  It's a fairly inexpensive part and should be easy to do if you already have the clamshell off.

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1 hour ago, gwri8 said:

Mind you that I'm probably not the first one to come to with electrical issues, but back to what @SteveJ mentioned, did you check your ignition switch?  It's a fairly inexpensive part and should be easy to do if you already have the clamshell off.

Is it fine to just check with a multimeter? Or should I buy a back up.

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Multi meter should be able to handle the diagnosis

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Just tested the ignition switch as the FSM details and it has continuity across the correct pins at the correct positions.

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Also check for any wobble in the pins.  I just had one that tested ok but one of the pins was loose and created an intermittent problem.

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First verify the battery is good. A bad battery or charging system with the accompanying voltage drop could account for some of the issues. Get the battery load tested. Don't try running the car with a low battery. You can damage things that way. By the way, what is the battery voltage right now? Check with a meter, not the voltage gauge on the dash. I'll trust a 40 year old Simpson meter. I'm not sure I would completely rely on the 40 year old voltage gauge.

Verify the presence/absence of spark with an inline spark tester (https://www.harborfreight.com/90-in-line-spark-checker-63593.html). Have someone crank the ignition while you watch for spark. Do this in a relatively dark setting.

Again, look for wiring modifications from a previous owner.

Search on this site. I know I have provided diagnostics for the 78 fuel pump relay and even described how to bypass the relay for testing.

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@SteveJ here are some pictures if you want more specific ones I can take more. Also the battery is at 12.97V

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Edited by Usain_Boat
Misspelled if and added battery info

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It runs again... I cleaned all the contacts again for peace of mind before dinner, plugged it all back in and nothing. Then after dinner I started tracing power through the relays that turn on the fuel pump since i didn't have power there and I had power through the fuel pump control relay to the fuel pump relay and too the pump. I am very confused as I did nothing in between the two times and tested no voltage to the fuel pump before dinner and I have power after dinner. A possible clue is as I said I had no dash lights or gauges earlier, when I went to try and start it after testing I had dash lights and gauges again.  After all I've been through with this car I highly doubt anything is actually fixed but I am confused as to what the problem could be.

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Sorry if I'm posting too much tonight but I just want to give as much information from my side as possible. After the car decided to turn back on It was back to the title of the thread, turning off when shifting into reverse. I stuck my probe of the multi meter into the plug at the very beginning of the fuel pump +, stuck the other to ground, turned on the car, took off the e-brake, braked, clutched in, and shifted into reverse. I then watched the voltage to the pump drop to zero and the car turned off. I turned it off and tried to turn it back on but no dice. I then clutched in with the key in on, heard a click, dash lights and gauges came back on and then it would run again. I tried to replicate the turning off in reverse probing other wires but I wouldn't shut off again.

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You're not posting too much. You are providing detailed observations. From this I can look at the wiring diagram and try to find some things for you to look at.

Did you strip off the wrapping around the wiring harness, or was that the work of a previous owner?

Clip from Picture 1.png

From picture 1, I can't tell if those are factory splices in the background.

Clip from Picture 3.png

From picture 3, is that the end of a wire that has been cut?

From my previous comment, it sounds like someone was trying to fix something and may have introduced a short. Just wild speculation, but it may be that the power for the second fuel pump relay coil or the fuel pump itself gets shorted out with the reverse switch. The car dies (and the damaged circuit loses power) before a fuse or fusible link is blown.

If you can get under the car easily and access the reverse switch on the transmission, take it out and see if that resolves the car dying when going into reverse. Also while you're under the car, see if either side of the reverse switch has continuity to ground.

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It sounds like the reverse switch is shorting something, there are two solid green wires from the reverse switch, one goes straight to the reverse lights the other goes to the voltage gauge charge light, the low fuel warning light, the flasher fuse in the main fuse box and the hazard switch. ALL of the connectors in those two lines should be pulled apart, inspected and cleaned to eliminate them as a cause.

I'm using the wiring diagram for a 77/ 280z

Edited by grannyknot

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I got the front end on ramps and took a look at the reverse switch leads. The two female bullet connectors on the harness were very dirty so I cleaned them. One is continuous to ground and the other isn't. On the switch itself both male leads aren't continuous to ground. I'm not sure if it's advisable but I have continued removing the outer insulation on the harness to follow the reverse wires. 

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Here are more pictures of the wiring harness undressed from where the reverse switch wires leave to the fuse box. Nothing looks "fixed" to me.

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get some electrical contact cleaner and spray every connector's pins (both sides) then make and break each connection 5 times and wiggle the connector while doing it.

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