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Usain_Boat

78 280z turns off with turn signal/reverse lights

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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. 

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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. 

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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

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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 by Usain_Boat

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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?

 

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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.

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So I got the car to die this morning and just tried to follow the power back. The Ignition relay is still on but i have like 60mV across the whole line even back to its fusible link. I decided to follow most of the circuit and take resistance measurements which are as follows. Fusible link to ignition relay: 0 Ohms

Across ignition relay: 0 Ohms

Ignition relay to fuse block: 5 Ohms to the fuse and 7 Ohms to the green wire side of the flasher fuse.

Ignition relay to C4: 0 Ohms

Ignition relay to fuel pump control relay: 4.5 Ohms

Fuel pump relay to Fuel pump control relay: .1 Ohms

To be clear, this is following the White/Red wire from the fusible link to the ignition relay where it leaves as a White/Black wire. 

Another observation I made through this process was the ignition relay got noticeably warm while there was 60mV on the circuits above. Could my ignition relay have an internal short that is causing this? Because if I understand the ignition relay shouldn't have enough resistance to get hot.

I also checked for power from the Black/White wire from the ignition switch and it is showing 12.8 V so the ignition relay should definitely be on.

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15 minutes ago, Usain_Boat said:

So I got the car to die this morning and just tried to follow the power back. The Ignition relay is still on but i have like 60mV across the whole line even back to its fusible link. I decided to follow most of the circuit and take resistance measurements which are as follows. Fusible link to ignition relay: 0 Ohms

Ignition relay to fuse block: 5 Ohms to the fuse and 7 Ohms to the green wire side of the flasher fuse.

Ignition relay to fuel pump control relay: 4.5 Ohms

These numbers seem high to me. The resistance across wire runs should be very low. You may want to validate your readings. Keep in mind that the quality of the probe with the wire being measure can greatly affect your readings. Make sure you have very firm contact on each side of the circuit.

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2 hours ago, Usain_Boat said:

Another observation I made through this process was the ignition relay got noticeably warm while there was 60mV on the circuits above. Could my ignition relay have an internal short that is causing this? Because if I understand the ignition relay shouldn't have enough resistance to get hot.

The 280Z's have the relay in a bad spot.  Gets wet if there's a leak.  They're easy to take apart, just bend the crimped lock tabs back and pull the cover off.

image.png

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Well I went with a hunch and built a new ignition relay out of two 40 amp SPST relays like @SteveJ  (I believe) outlined on zcar.com and it still dies in reverse. I took the readings aforementioned by sticking the probes in the back of the connectors while it was dead so I could keep it in the state that kills the car. It is possible they aren't the best readings. If I was to take them again, what would be the best way? 

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Just opened the ignition relay as best I could and Its not rusty inside, the ground is still attached and I would rather not break it so I wasn't able to open it all the way.

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5 hours ago, Usain_Boat said:

So I got the car to die this morning and just tried to follow the power back.

It's not clear why the engine needs to be running for this problem to manifest itself.    Also not clear that the fuel pump power is the main reason the engine dies.  Seems more like you're losing all ignition relay power, not just fuel pump power.  Do other things shut down?  Radio, heater blower, windshield wipers, etc.  Those are accessory items but I think that they use the same supply line to the ignition relay.  Also, voltage to the coil should go away if it's an ignition relay problem.

Maybe connect a test light or two to your ignition relay's input and output then put it in and out of reverse and see if something different shows up.

And don't forget the Hazard switch.  It is the cause of many mysterious electrical problems.

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Just now, Zed Head said:

It's not clear why the engine needs to be running for this problem to manifest itself.    Also not clear that the fuel pump power is the main reason the engine dies.  Seems more like you're losing all ignition relay power, not just fuel pump power.  Do other things shut down?  Radio, heater blower, windshield wipers, etc.  Those are accessory items but I think that they use the same supply line to the ignition relay.  Also, voltage to the coil should go away if it's an ignition relay problem.

Maybe connect a test light or two to your ignition relay's input and output then put it in and out of reverse and see if something different shows up.

And don't forget the Hazard switch.  It is the cause of many mysterious electrical problems.

I took apart and cleaned the hazard switch recently to get the turn signals work so what should I look for wrong there?

The power from the ignition switch to the ignition relay doesn't die, the Black/White wire at the relay still has 12.8 volts so that should have the coil energized and the relay still on. The problem is the voltage on the circuit that provides power to the flasher fuse, fuel pump control relay, and fuel pump relay loses power. This is the White/Black wire when it leaves the ignition relay. The Black/White wire that comes from the ignition switch has power at the relay, I'm not sure if it loses power in a shutdown event. I haven't tested anything else to be dead but next time I will test the wipers and blower.

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9 minutes ago, Usain_Boat said:

The power from the ignition switch to the ignition relay doesn't die, the Black/White wire at the relay still has 12.8 volts so that should have the coil energized and the relay still on. The problem is the voltage on the circuit that provides power to the flasher fuse, fuel pump control relay, and fuel pump relay loses power. This is the White/Black wire when it leaves the ignition relay.

You just described a bad relay.  Not sure why your fabbed-up relay didn't work.  You're saying that the coil is energized but the switch is not transmitting power.

Be the relay.  Short across the circuit in the relay that you think is losing power.  If it fixes the problem then the relay is bad, either  the contacts are dirty or the solenoid isn't working.  If it doesn't fix the problem then you can move on from the relay.

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23 minutes ago, Zed Head said:

You just described a bad relay.  Not sure why your fabbed-up relay didn't work.  You're saying that the coil is energized but the switch is not transmitting power. Be the relay.  Short across the circuit in the relay that you think is losing power.  If it fixes the problem then the relay is bad, either  the contacts are dirty or the solenoid isn't working.  If it doesn't fix the problem then you can move on from the relay.

So when I was testing while the car was dead, the relay had continuity across the contacts from the White/Red from the fusible link to the White/Black. Therefor the relay was working as intended I believe. The problem is that 60 mV on the circuit is not going to be enough to energize the fuel pump control or fuel pump relays that are on that wire. Also, the reverse lights are not on either since there is not enough voltage to run them. Through all of this the car will die once but as soon as you shift out of reverse and restart the car it won't do it again for a while.

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Don't assume that continuity and low voltage mean the relay contacts are making good contact.  Sounds like you have a bad relay.  The test I described will show you if that's the case.

The measurements only get you so far, typically showing what's working correctly.  Your measurements have shown you that something is not right in the relay.  The next step is testing.

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35 minutes ago, Zed Head said:

Don't assume that continuity and low voltage mean the relay contacts are making good contact.  Sounds like you have a bad relay.  The test I described will show you if that's the case.

The measurements only get you so far, typically showing what's working correctly.  Your measurements have shown you that something is not right in the relay.  The next step is testing.

Ok, I will keep testing with the ignition relay completely bypassed.

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45 minutes ago, Usain_Boat said:

Engine still died with the ignition relay bypassed.

This is actually a good thing.  Now you can look elsewhere for the source of the problem.

Try to determine if you're losing ignition power, fuel pump power, or both.  That will be a clue.

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Try disconnecting the connectors 1 at a time to the lights switch/wiper switch in the steering column and see which one causes the problem. Watch out for the power cables from shorting.

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Well I've already traced power for those circuits. I lose power at the fuel pump relay output (the relay clicks off) and I also know I lose power on the wire that provides power to the solenoids in the fuel pump control relay and fuel pump relay. I think a big clue is this is the same wire that provides power through the flasher fuse to reverse and turn signals. Though I blow no fuses! So I'm not sure. If I'm not blowing the flasher fuse or the fusible link for that circuit, should I be looking ahead of the fusible blink at the white wire that powers the fusible link?

If I pull the flasher fuse the car doesn't die either, though it not blowing that 10A fuse is confusing.

Edited by Usain_Boat
Added information on the flasher fuse

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