78 280z turns off with turn signal/reverse lights

[Usain_Boat]

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... 

[Usain_Boat]

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 August 3, 2019 by Usain_Boat
Specified what I bypassed

[gwri8]

Is this what yours looks like?  https://zcardepot.com/collections/sending-units/products/oil-pressure-sender-switch-sending-unit-77-83

[Usain_Boat]

1 hour ago, gwri8 said:

Is this what yours looks like?  https://zcardepot.com/collections/sending-units/products/oil-pressure-sender-switch-sending-unit-77-83

Yes it's one with a two prong "T" connector. Not the 240/260 one. It's just an import direct one from O'Reilly.

[Zed Head]

The fuel pump control system uses the alternator output as a control signal also.  So bypassing the oil pressure switch shouldn't have been necessary.  Doesn't really make sense, if you're saying that a bad oil pressure switch stopped your fuel pump power.,  

I haven't read the whole thread, it starts off as a turn signal/reverse switch problem. 

[Usain_Boat]

19 hours ago, Zed Head said:

The fuel pump control system uses the alternator output as a control signal also.  So bypassing the oil pressure switch shouldn't have been necessary.  Doesn't really make sense, if you're saying that a bad oil pressure switch stopped your fuel pump power.,  

I haven't read the whole thread, it starts off as a turn signal/reverse switch problem. 

Yeah It wasn't necessary, on further testing it does nothing and the car still dies. I have found out that the Fuel pump control relay loses power on the white/black stripe wire when the car dies in revere and the power is returned as soon as it is taken out of gear. So, as @SteveJ has suggested, something is probably causing a MAJOR voltage drop when the turn signals or reverse come on. Or, they are somehow turning off the ignition relay. 

[wal280z]

On 7/29/2019 at 8:01 PM, Usain_Boat said:

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.

Please explain on how the blocks are wrong in the wiring diagram.  What diagram are you using?

There was much discussion on how the wiring diagrams were messed up regarding the LOCATION of the fusible links on the front fuse block, see the thread by @EuroDat on fusible links.

Wayne

[Usain_Boat]

50 minutes ago, wal280z said:

Please explain on how the blocks are wrong in the wiring diagram.  What diagram are you using?

There was much discussion on how the wiring diagrams were messed up regarding the LOCATION of the fusible links on the front fuse block, see the thread by @EuroDat on fusible links.

Wayne

Ok, so the forward most inside fusible link block is shown to run to the bus bar that feeds the flasher fuse on the fuse block. Its actually on the rear block if i remember correctly. I'm using the 78 color wiring diagram.

Edited August 5, 2019 by Usain_Boat

[SteveJ]

@Usain_Boat- This is the thread @wal280zis referring to 

 

[Usain_Boat]

So I have my fusible links set up like @Captain Obvious black in the front outside and red in all the other positions.

[Zed Head]

4 hours ago, Usain_Boat said:

Yeah It wasn't necessary, on further testing it does nothing and the car still dies. I have found out that the Fuel pump control relay loses power on the white/black stripe wire when the car dies in revere and the power is returned as soon as it is taken out of gear. So, as @SteveJ has suggested, something is probably causing a MAJOR voltage drop when the turn signals or reverse come on. Or, they are somehow turning off the ignition relay. 

Fuel pump control relay loses power on the white/black stripe wire when he shift lever is put in to  reverse

power is returned as soon as the lever is taken out of reverse

Have you tried disconnecting the reverse switch to see what happens?  It might not be a high current draw but instead one of the circuits to the control relay is getting grounded, causing the control relay to cut power.

The control relay system operation just never sticks in my head. but I think that the oil pressure switch is closed at low pressure, grounding that circuit.  Seems like it might be possible that your reverse circuit and oil pressure switch circuit have been swapped.  When you actuate the switch, grounding that circuit, it looks low oil pressure to the control relay.  Are your reverse lights on when the key is on and engine not running?

 

[Usain_Boat]

16 minutes ago, Zed Head said:

Fuel pump control relay loses power on the white/black stripe wire when he shift lever is put in to  reverse

power is returned as soon as the lever is taken out of reverse

Have you tried disconnecting the reverse switch to see what happens?  It might not be a high current draw but instead one of the circuits to the control relay is getting grounded, causing the control relay to cut power.

The control relay system operation just never sticks in my head. but I think that the oil pressure switch is closed at low pressure, grounding that circuit.  Seems like it might be possible that your reverse circuit and oil pressure switch circuit have been swapped.  When you actuate the switch, grounding that circuit, it looks low oil pressure to the control relay.  Are your reverse lights on when the key is on and engine not running?

 

The reverse lights only turn on when the trans is in reverse and the car doesn't turn itself if in reverse with the switch unplugged. However even with this done, the turn signals still turn it off (confirmed the left does it not sure on right). And just to confirm, I'm talking about the white and black from the ignition relay that provides power to the control relay and not the one that turns on the fuel pump relay itself.