Wiring for switch/push button ignition

[perry]

Anyone versed or patient enough to help me with a electrical issue? I am trying to install a switch and push button system on my 73 240 in lieu of the old key switch. Things looked like they would work but something has me confused. I hope my description instead of a drawing works;

1) White/Red wire brings power to the on/off switch, which passes the power onto the momentary push button, which in turn allows power to the starter via the Black/Yellow wire. This seems to work fine.

2) I have tapped into the wire between the switch and push button with the Black/White wire that supposedly runs to the fuse panel and seems to run the fuel pump(among other things?). This seems to power up the electric fuel pump as I can hear it. However, it also turns the starter over.??? Why, I don’t know because that is what the signal from the push button to the Black/Yellow wire also does. The car is trying to start but the starter is still engaging so I have to stop everytime.

Anyone have any good suggestions or a better understanding of what I may have done incorrectly?

[240ZX]

Perry, Here's what I'd do if I were in your position. Purchase a shop service manual first off! It will have wiring diagrams showing all the wires/coding. Take a look at the starting circuit. It should provide you with enough information (as long as you have a good basic understanding of DC circuitry)to replace the original key start set-up to a manual power switch and start swithch. A test-light probe (for power on testing) and a continuity meter (one of the functions of an Ohm meter and for power off testing) will also be something you will want for this exercise. Hope this gets you pointed in the right direction!

Tom

[Ed]

O.K., I'll ask, why are you replacing the key with a push button?

[perry]

a system that seems to be operable by anyone with worn keys like mine. That and I don't want to spend hundreds of dollars replacing the ignition with a new one. Then there is the issue of needing a different key for the door locks.

It also gives other security as I can hide the switch and the button.

[Arne]

There is a lot more to wiring this up than first appears to the eye, as the ignition switch itself is fairly complex. For example, on a 240Z the switch has two wires to energize the coil - one in the run position, and one in the start position. Some circuits get power in the accessory position, others in the run position. To do it right will take some studying of the diagram so that you understand what functions the original switch is providing.

Frankly, I understand electrical quite well, but I'd far rather replace the worn lock tumbler than re-wire the ignition.

[EScanlon]

Perry:

The only reason I can think of that would cause what you post is that you have a crossed wire somewhere. Specifically the B/W wire should NOT actuate the starter.

Let me describe the wiring at the Ignition Switch. This is accurate for the 70-73 years.

The Ignition Switch, attached to the back of the Steering Lock on the Steering Column has the following FIVE (5) wires connected to it via a 2x3 Male Spade Connector.

Black / Yellow (B/Y)

Black / White (B/W)

White / Red (W/R)

Blue / Red (L/R)

Green / White (G/W)

Using Nissan's color legend initials.

Their function / connection is:

B/Y: When the Ignition Switch (IS) is in the START position, it routes power from the IS to the Seat Belt Sensor (K-18) Relay and / or the Automatic Transmission Switch Inhibitor, then to the Starter Solenoid. If either the SBS or the ATSI are open then no power and no start. This wire is only active in the START Detent.

B/W: Routes power to the Resistor in the engine bay which then returns it to the Tach via a Green / White wire. That G/W wire then connects to the G/W wire also attached to the IS which also routes power to the Tach. The Tach then sends power to the Coil via a B/W wire. This B/W wire also powers the Flasher fuse at the Fuse Box. Also connected to this wire are: Kick Down Switch (AT Only), Oil and Temp Gauge Sensors. This wire is only active in the RUN detent.

W/R: This wire brings power TO the ignition switch directly from the Fuse Box. It also shares power with the Accessory Relay. On most wiring diagrams the connection to that wire was not annotated, and is misleading. The wire DOES connect with the wiring going to the Acc. Relay. This wire is live ALL of the time and connects in all 3 detents: Accessory, Run and Start.

L/R: Routes power to the Heater Blower, the Accessory Relay, and the Wiper and Accessory Fuses. This wire is only active in the RUN detent.

G/W: Routes power to the Tach and then to the Coil. This bypasses the Resistor. Only active in the START detent.

The reason you're having the "issue" you're experiencing is that you are NOT disconnecting the B/W and L/R when you're connecting the B/Y to the W/R.

To connect a Momentary SPST switch for the Starter, you need to connect this downstream of a DPDT-Center Off switch.

The DPDT-Center Off switch will have both center terminals connected to the W/R, then in the Upper two connections, the B/W and the L/R. In the Lower two connections you'll have the B/Y and the G/W. The B/Y will then be connected to the Momentary SPST. To actuate the system you'll put the DPDT-CO connecting the LOWER contacts, and then actuate the Momentary. This will power the G/W wire (and hence the coil) and allow you to momentarily power the starter via the B/Y. The engine will start, but no accesories will be powered. Then quickly flick the DPDT-CO to the opposite position (connecting the UPPER contacts) and you'll be able to power the accessories.

I'm sure there's a way to make it so that you wouldn't have to flick the DPDT switch, but this will get you working.

All of this having been written and re-checked, you might find that it isn't that hard to find a good Steering Lock Cylinder, and the Ignition Switch behind it. Heck, it might prove to be MUCH easier than re-wiring everything.

But that's just my 2¢

E

[perry]

Wow...that's alot more then 2cents. When I get time this weekend to digest your thoughts I will get back to you. Thanks.

[=Enigma=]

Post deleted to avoid confusion....

[EScanlon]

I was using the wiring diagram from my FSM to trace all that out. It concurs with the one in the original Clymer's. I use both because the FSM manual for my year doesn't include the Accessory Relay in the diagram, nor info about the AT's.

This could well be a case where the wiring is different for short lengths, but not overall. I've had that happen with several cars.

I also note that the diagram you are using is one that is similar to one I found at AutoZone (or some such), and while they're very good and complete, there are just a few differences.

Sadly, even the FSM has errors in it. Sometimes these errors never got corrected in subsequent editions. I mentioned one above, and there's at least one or two more IIRC.

Good to point that difference out, however, as it would certainly befuddle anyone looking at the connector (if it applied).

E

[=Enigma=]

E, you're absolutely right on where that diagram came from. I removed it to avoid confusion.

I took a look at my 73' FSM and the diagrams for 70-75 in the Clymers manual I have, and all of them concur with the info you posted. I couldn't read the wiring colors for the IS on the 76-78 diagrams. They were just too small even for my eagle eyes and I couldn't find a magnifying glass.