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Usain_Boat

78 280z turns off with turn signal/reverse lights

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59 minutes ago, 240260280 said:

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.

So I cleaned them again with Deoxit and got some more connectors while I was at it too. The oil pressure connector hadn't been cleaned before and I know that is part of the fuel cutoff so maybe that will help.

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4 hours ago, Usain_Boat said:

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. 

Okay, this is a good start. If you have not already done so, download a copy of the FSM from this site. (If you are on a computer, the link is in my signature.) Also, look at Blue's tech tips for a copy of the full wiring diagram. I think there is even a color copy of the wiring diagram floating around this site somewhere.

On page BE-14 of the FSM, you'll find the reverse light circuit. The diagram shows that one side of the switch gets power from the fuse box, and the other goes to the taillights. Neither side should be grounded. Since you say one side of the switch is grounded, let's assume that is the side with the bulb sockets. Unplug both of your taillights at the taillight panel. Check the wire that had continuity with ground to see if it is still grounded. If it is not, the problem is at a taillight. That might also correspond to the dying problem happening with the turn signal.

If the wire is still grounded after that test, break the connection at connector C-4. Test again. If it is grounded, the problem exists between the switch and connector C-4. If it is not grounded, there is a chance the body wiring harness is damaged, probably by a screw and is grounding out. To trace the path of the body harness, look at the BE section of the FSM.

If my instructions don't make sense, send me a PM with your phone number. Sometimes I can explain this over the phone more easily than I can type it up.

 

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I have the FSM and the color wiring diagram that I'm using currently. Just to get on the same page, as far as I know the wire that goes from the reverse switch to the reverse lights should be grounded since it just powers one of the bulbs leads and the other is grounded to the chassis. If not, what should it be/not be continuous to?

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1 minute ago, Usain_Boat said:

I have the FSM and the color wiring diagram that I'm using currently. Just to get on the same page, as far as I know the wire that goes from the reverse switch to the reverse lights should be grounded since it just powers one of the bulbs leads and the other is grounded to the chassis. If not, what should it be/not be continuous to?

The wire that goes to the bulbs is not continuous to ground. The bulbs are the load (resistance). You should be reading about 3 Ohms resistance from the wire at the switch to ground. Only the negative side of the bulb socket should have continuity to ground.

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@SteveJ Starting to test the reverse circuit for shorts and the hot side from the fuse box is now continuous to ground with a 21 Ohm resistance. The side to the reverse bulbs is continuous with about 1.3 Ohms resistance with the bulbs in and no continuity with them unplugged.

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Ok so the 21 Ohms resistance to ground comes from the Yellow/Red stripe wire that goes to the seatbelt warning timer. Is this correct functionality? Nevermind, timer has 2.1 kOhms resistance to ground the 21 Ohms I was seeing is through the fuel gauge fuse as they share the same positive bus to the fuses.

Edited by Usain_Boat
Correcting information (Incorrect Resistances)

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If I'm reading the wiring diagram correctly, the white with black stripe wire that turns on the fuel pump relay is the same that supplies power to the flasher fuse and fuel gauge fuse. So, given I don't have dash gauges/lights when the car won't turn on or turns itself off it should be a problem within those circuits. Also since I'm not blowing fuses, could it just be a bad connection in the white with black stripe wire supplying power to the reverse circuit being overloaded, then the relay for fuel turns off?

Edited by Usain_Boat
Made a sentence more clear

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Digging deeper I do remember some splices in for the connections to the fusible link that I thought I fixed from the PO. When I got the car there were heat shrink crimps where the plastic was cracked and gone so I took them off and redid them. The fusible link in question (I believe it's the one closest to the engine in the front) has some green corrosion within the crimp and I also didn't get all the strands into the crimp. If I was to cut all of this out and redo it what gauge wire should it be? It looks heavier than the 14 gauge I have and is getting pretty short from whatever the PO did.

Screenshot_20190728-133201.png

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36 minutes ago, Usain_Boat said:

Digging deeper I do remember some splices in for the connections to the fusible link that I thought I fixed from the PO. When I got the car there were heat shrink crimps where the plastic was cracked and gone so I took them off and redid them. The fusible link in question (I believe it's the one closest to the engine in the front) has some green corrosion within the crimp and I also didn't get all the strands into the crimp. If I was to cut all of this out and redo it what gauge wire should it be? It looks heavier than the 14 gauge I have and is getting pretty short from whatever the PO did.

Screenshot_20190728-133201.png

You should do the Cadillac upgrade that @wal280z came up with. 

I can't find on this phone but will with my lapdance.

 

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I like to solder connections when ever possible. Especially some where , like there, under the fusible links

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2 minutes ago, Patcon said:

I like to solder connections when ever possible. Especially some where , like there, under the fusible links

How powerful of a soldering iron do you have? Using a 15w one I was struggling with 14 gauge

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Daily update: took apart every connector I could find that might be part of the problem and cleaned them very well including the leads for all the relays, the fusible link terminals and other things. After doing this I plugged everything up fired it up and shifted into reverse which killed it again Though this time, I could shift in and out of reverse and hear some relay (wasn't able to track it down) click on and off while the dash lights (batter charge and brake indicator) turned on and off with shifting into reverse. After about 10 times the car quit doing it so I was not able to test anymore.

 

Edited by Usain_Boat
Last sentence had typos

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Okay, here is an explanation of the fuel pump control relay and fuel pump relay

78 Fuel Pump Relay Notes
There are two relays
1. Fuel Pump Control Relay
2. Fuel Pump Relay

Fuel Pump Control Relay:
Positive coil voltage comes from the white/black wire (Origin is the Ignition Relay)
One coil is grounded through Alternator (blue wire).
The other coil is grounded through the oil pressure switch (yellow/black).
The relay has form C contacts.
A contact puts wiper (white/black) in contact with power from ignition relay.
B contact puts wiper in contact with power from engine cranking (black/yellow wire).
(Note: This is opposite of how it is drawn in the factory wiring diagram, but how it is drawn does not make sense.)
The wiper provides coil power to the Fuel Pump Relay.

Fuel Pump Relay:
Positive coil voltage comes from the white/black wire from the Fuel Pump Control Relay wiper.
Form A contacts connect two green/blue wires. One side comes from a fusible link. The other side goes to the fuel pump.

Theory of operation:
When cranking the engine, within the Fuel Pump Control Relay, the second white/black wire mentioned above is connected to the start position on the ignition switch. This energizes the Fuel Pump Relay and powers the fuel pump.
If the engine starts, the key is released to the ON position, and the first white/black wire is energized from the ignition relay. The blue wire is grounded through the alternator and the coil is energized within the Fuel Pump Control Relay. This closes a set of contacts within the Fuel Pump Control Relay that allows the second coil to energize, provided there is sufficient oil pressure. With the second coil energized, the power from the ignition relay is providing power to energize the coil on the fuel pump relay.

How this applies to your problem:

The odds are that the voltage is dropping on the white/black wire coming off the ignition relay.

List of components fed from the white/black wire from the ignition relay:
Fuel Pump Control Relay
Electronic Fuel Injection Main Relay
Flasher fuse (Green wire)
Fuel Gauge fuse (Blue wire)

The loads off the Flasher fuse:
Brake Warning Lamp Check Relay
Turn signals
Seat Belt Warning Timer Unit
Fuel Level Warning Lamp
Reverse Lights

The loads off the Fuel Gauge fuse:
Fuel Gauge
Water Temp/Oil Pressure Gauge
Tachometer

Process of Elimination:

There are several components here that we can definitely cross off as problematic: Fuel Pump Control Relay, EFI Main Relay, Seat Belt Warning Timer Unit, Fuel Level Warning Lamp, Fuel Gauge, Water Temp/Oil Pressure Gauge, Tachometer.

So IIRC, you said that the car would die when using turn signals or putting the car into reverse. Those are BOTH powered off the flasher fuse in the fusebox, and the flasher fuse gets its power via the white/black wire from the ignition relay.

There is even a common point for these two circuits that initiate the problem: the right rear taillight assembly.

Here is a simple test. Disconnect the wiring harness going to the right rear taillight assembly. Start the car and try to put it into reverse. If it does not die, try turning on the right turn signal. If it does not die, you have confirmed that the issue is at the right rear taillight assembly. You may have to take off the plastic panel to access the connector.

Right Rear Combination Lamp from Page BE-10.jpg

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Oh, since we would expect the flasher fuse to blow, check the rating on the fuse to make sure it is only 10A.

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18 minutes ago, SteveJ said:

Oh, since we would expect the flasher fuse to blow, check the rating on the fuse to make sure it is only 10A.

I've gone through them and it is 10A that's part of what's baffling me.

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FYI to the reading public, @Usain_Boat and I have talked on the phone. He is going to examine the body wiring harness for signs of damage. The cutting off may be happening with the left turn signal, too. The common path is through the body wiring harness. Fortunately, the interior panels are off so he can trace it more thoroughly.

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Took a look at the rear of the harness this morning and I don't see anything suspicious. The place where the electrical tape is where it was already peeling off so I peeled it back further to look. Attached are pictures

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5 hours ago, Usain_Boat said:

Took a look at the rear of the harness this morning and I don't see anything suspicious. The place where the electrical tape is where it was already peeling off so I peeled it back further to look. Attached are pictures

MVIMG_20190729_114123.jpg

Is it me or does this taillight harness appear to be spliced? (black heat shrink) 

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This evening I disconnected the reverse switch to isolate that and it died with the left turn signal. I could hear the ignition relay clicking on and off with the blinkers. At this point I know of two instances where the left turn signal has killed the car not sure on the right turn signal.

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On 7/28/2019 at 2:34 PM, Usain_Boat said:

Digging deeper I do remember some splices in for the connections to the fusible link that I thought I fixed from the PO. When I got the car there were heat shrink crimps where the plastic was cracked and gone so I took them off and redid them. The fusible link in question (I believe it's the one closest to the engine in the front) has some green corrosion within the crimp and I also didn't get all the strands into the crimp. If I was to cut all of this out and redo it what gauge wire should it be? It looks heavier than the 14 gauge I have and is getting pretty short from whatever the PO did.

Screenshot_20190728-133201.png

Question - Did YOU do the splicing, or just repair what was already done?

Did you OHM the connections prior to re-splicing? Wondering if one of those connections got switcher-ro'd.

There was a recent thread about fusible links created by @EuroDat and all evidence has pointed to the Factory wiring diagrams being incorrect from 1976-1978 - the front most fusible link holder being suspect.

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16 minutes ago, wal280z said:

Question - Did YOU do the splicing, or just repair what was already done?

Did you OHM the connections prior to re-splicing? Wondering if one of those connections got switcher-ro'd.

There was a recent thread about fusible links created by @EuroDat and all evidence has pointed to the Factory wiring diagrams being incorrect from 1976-1978 - the front most fusible link holder being suspect.

The splices were already done by the PO, I just replaced the crimps. I didn't check that they went to the correct places though I did notice Saturday that the front and rear blocks are wrong in the wiring diagram for 78.

Edited by Usain_Boat
Answered another question

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I have physically traced the entire reverse circuit and have found nothing obviously wrong. It was a wire that had been exposed earlier but I have already cut that section out and reconnected it with a weatherproof crimp. So now I'm suspecting the reverse switch itself to have a problem. It might should have been checked earlier since I did just replace it when trying to get reverse lights working... 

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So I bypassed the fuel cutoff from the oil pressure sending unit today and that may have fixed the issue. I know this is a terrible solution and don't plan to do it more than for testing so the next question is what would be a good recommended oil pressure sending unit to replace the Chinese one on it now?

To specify, I bypassed the fuel cutoff in the oil pressure sending unit

Edited by Usain_Boat
Specified what I bypassed

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