260z interlock TSB

[YZFMax]

Bringing this thread back up as I'm also experiencing similar issues.

I was reviewing the wiring diagrams for the 260Z interlock and comparing it to the 240Z wiring diagram for the starter.  The 240Z basically has a direct connection from the ignition switch to the starter motor, there is no interlock unit or relays.  Has anyone tried doing this to the 260Z and bypassing the interlock, seat belt and emergency switch altogether?  I would be adding a starter relay in between the ignition switch and the starter motor.

Seems like the previous owner already disconnected the seat belt relay, so this is already being bypassed.  

[anthony_c]

it's been several months since i looked at the wiring diagram, but before your completely bypass the interlock watch out for the fuel pump relays. one of them is triggered by the interlock system.

[YZFMax]

2 minutes ago, anthony_c said:

it's been several months since i looked at the wiring diagram, but before your completely bypass the interlock watch out for the fuel pump relays. one of them is triggered by the interlock system.

Interesting.... the previous owner also indicated that he added a fuel pump relay, so now I will have to trace this back.  Thanks for the heads up!

[anthony_c]

the 260 has (or at least mine does) two factory fuel pump relays. one triggered by the alternator, the other by the interlock relay.

and if i could i would yank the whole mess and switch to a mechanical fuel pump.

[heyitsrama]

I have done extensive rewirings of an early 260z. I did remove the interlock unit, and the emergency switch.

IIRC For the starter I used the yellow wire as a trigger on a relay for the solenoid, i was having   a starting issue that never came back after I did that modification. 

I wired in a separate relay for the fuel pump (no mechanical pump). Which is turned on by a wire that comes off the ignition key circuit (green/white?)

I hate the wiring in the car, it works but it’s ugly, at some point I’ll pull it out and redo it all again.

 

[YZFMax]

This helps and does put me in the right direction.  Thanks!

[SteveJ]

6 hours ago, anthony_c said:

it's been several months since i looked at the wiring diagram, but before your completely bypass the interlock watch out for the fuel pump relays. one of them is triggered by the interlock system.

Actually, the bypasses that I suggested should not adversely affect the operation of the starter fuel pump relay. That fuel pump relay actually cuts power to the fuel pump while cranking.

[YZFMax]

On 12/1/2020 at 3:27 PM, SteveJ said:

Actually, the bypasses that I suggested should not adversely affect the operation of the starter fuel pump relay. That fuel pump relay actually cuts power to the fuel pump while cranking.

 

On 12/1/2020 at 9:27 AM, anthony_c said:

the 260 has (or at least mine does) two factory fuel pump relays. one triggered by the alternator, the other by the interlock relay.

and if i could i would yank the whole mess and switch to a mechanical fuel pump.

I think I found a solution for the fuel pump relay:

Fuel Pump Safety Switch (revolutionelectronics.com)

This should address the safety concern with the fuel pump staying on if the engine unexpectedly shuts down.  If the system does not sense a signal from the tach, then it will cut off the power to the fuel pump.   

With this, I should be able to run a direct connection from the ignition switch to the starter (via a relay), and eliminate both the interlock and the dual factory fuel pump relays.

[anthony_c]

i like it, my only concern is that is a one-off product. what happens when it fails and replacements are nla.

[SteveJ]

8 hours ago, YZFMax said:

 

I think I found a solution for the fuel pump relay:

Fuel Pump Safety Switch (revolutionelectronics.com)

This should address the safety concern with the fuel pump staying on if the engine unexpectedly shuts down.  If the system does not sense a signal from the tach, then it will cut off the power to the fuel pump.   

With this, I should be able to run a direct connection from the ignition switch to the starter (via a relay), and eliminate both the interlock and the dual factory fuel pump relays.

That is a little overkill for the 260Z. There isn't a need to prime on a 260Z with carburetors because the car will start with the fuel in the float bowls. If you are looking to cut the fuel pump when the engine isn't running, you can wire the car to use the ignition to power the relay coil and get a 78 oil pressure sender. Swap in a typical automotive relay and wire the negative of the new relay to the grounding terminal on the oil pressure sender. If the oil pressure drops too low (such as when the engine isn't running), the ground opens up, and the coil is de-energized. For additional safety, you could mount an inertia switch to kill power in case of an accident.

Inertia switch: https://www.amazon.com/gp/product/B07RBK4873

Oil pressure sender: https://www.rockauto.com/en/moreinfo.php?pk=488596&cc=1209260&jsn=1305

As an aside, I found a mystery wire in my 260Z many years ago. It came off the ignition coil positive and was routed through the passenger cabin to the back right. Apparently it was an IPO's effort to hot-wire the fuel pump. I don't know why. The stock wiring was working. I just can figure out how the wire didn't short to the body since the insulation was in poor condition.

[YZFMax]

10 hours ago, anthony_c said:

i like it, my only concern is that is a one-off product. what happens when it fails and replacements are nla.

True, but for me this is a temp solution until I convert the carbs to EFI.  Then the ECU will be used to control the fuel injection relay.

[YZFMax]

1 hour ago, SteveJ said:

That is a little overkill for the 260Z. There isn't a need to prime on a 260Z with carburetors because the car will start with the fuel in the float bowls. If you are looking to cut the fuel pump when the engine isn't running, you can wire the car to use the ignition to power the relay coil and get a 78 oil pressure sender. Swap in a typical automotive relay and wire the negative of the new relay to the grounding terminal on the oil pressure sender. If the oil pressure drops too low (such as when the engine isn't running), the ground opens up, and the coil is de-energized. For additional safety, you could mount an inertia switch to kill power in case of an accident.

Inertia switch: https://www.amazon.com/gp/product/B07RBK4873

Oil pressure sender: https://www.rockauto.com/en/moreinfo.php?pk=488596&cc=1209260&jsn=1305

As an aside, I found a mystery wire in my 260Z many years ago. It came off the ignition coil positive and was routed through the passenger cabin to the back right. Apparently it was an IPO's effort to hot-wire the fuel pump. I don't know why. The stock wiring was working. I just can figure out how the wire didn't short to the body since the insulation was in poor condition.

Thanks for the advice.  I will definitely look into this, specially the inertia switch.