Late 260Z Electric Pump Cut Relay Connectors

[Tuner Galleria]

Hello,

 

I recently picked up a late '74 260Z and have been going through some of the wiring. I came across these 2 connectors that are unconnected with one wire jumped. One connector should be going into a relay, while the other into the male side of the corresponding harness. A search in the FSM suggests that the connectors are the electric pump cut relay #1 and #2.

 

The wire that is jumped is black with white stripe.

 

Which systems are affected by these 2 connectors not being connected in the factory manner? Why is the black w/ white stripe being jumped?

 

Thanks in advance for any advice and sharing of knowledge.

 

http://razzi.me/p/85...http://razzi.me/p/858034

http://razzi.me/p/85...http://razzi.me/p/858035

Edited November 19, 2012 by Tuner Galleria

[Leon]

I did the something similar in my early 260Z.

 

If you look at the wiring diagram, the jumper bypasses the cut relays and runs the pump all the time with key ON. This also takes out all fuel-pump shutoff devices in case the car is in an accident, thus the pump will keep pumping fuel even with the engine dead, the car upside-down, etc.

 

As you will find in the FSM, cut relay #1 deactivates the pump if engine speed goes below 400rpm and cut relay #2 kill the pump during cranking.

[Tuner Galleria]

Leon, thanks for the reply. Earlier today, I performed the TSB to bypass the emergency switch in the engine bay for the starter interlock system. I was experiencing the common issue where you crank the key, and just hear clicks without the starter turning over. Initially I changed the ignition switch per recommendation of the previous owner, however that didn't solve the issue in my case. I was going to augment the power wire going to the starter with one of those pre-made wiring kits that have a relay sold through some datsun vendors. Then I came across this curious starter interlock that was present in my late 260Z. Now that the interlock system is bypassed, she starts right up!

 

Back to the original question, what would be the advantage to bypass these factory fuel pump fail safe systems? Do they commonly fail and thus owners bypass them as a cheap fix? I did notice today when I disconnected the jumper, I couldn't hear the fuel pump operating. However, the car still started without these 2 connectors being connected to the proper locations. I did not try driving though.

[Leon]

I had the same starting problem, I bypassed the interlock and wired in a $5 relay. No problems since.

 

As far as bypassing the factory fail-safes, I did it to have pump priming capabilities for starts after long periods of sitting. Then, shortly thereafter, I completely removed the factory electric pump. I've been running fine with the mechanical pump ever since.

[Tuner Galleria]

Leon, I've got another electrical issue...hopefully you can provide insight. When I bought the car, the blower fan didn't work and the previous owner never spent the time to diagnose so he just said there is a short somewhere. He pulled the fuse to the blower in the fuse box.

 

I put a 20A fuse and tried the blower at all 4 speeds, blower didnt work and also blew the fuse. I then disconnected the blower motor, replaced the fuse again, and tried the fan speed switch...only at fan speed 4 did the fuse blow. Which is the more likely culprit, fan speed switch, blower resistor or blower relay?

[Leon]

I haven't had any fan blower issues, so I'm not very familiar with that circuit. You'll just have to go through the typical procedure for finding a short. The FSM has a wiring diagram that shows the circuit nicely.

[Tuner Galleria]

The air conditioning 20 amp fuse blowing issue turned out to be the connector to the blower fan from the harness side.  The plastic connector between the 2 leads had melted enough to arc.  I replaced the connector with parts from Vintage Connections and everything works now.

[Leon]

Nice job!