620 DCH340 Carb Wiring Colors Don't Match Carb, Harness, or Manual

[Cardinal Grammeter]

First, I couldn't decide if this should be posted in the Electrical or 620 Forum.  If I don't get any replies here, I'll post the same topic in Electrical where I'll put a link to this thread with instructions to post replies here.

 

Here is my problem:  I can't determine how to connect the carburetor because my wiring harness wire colors do not match the wiring diagram so I don't know how the function of the harness wires.

 

Here is the Discussion:

 

I've gotten a used carb for my 74 620 4-spd and it is supposed to be from a 77.

 

I can read some of the ink stamp but not all.

 

Here is what I can see:  DCH  340-x5  where the x is not legible.  If I was forced to guess, it would be a 9.  But ending in 5 implies a manual trans carb which is good.

 

COLOR CONVENTION:  When I talk colors, the order will be Choke, anti-Diesel, then BCDD

 

I have both 73 and 74 service manuals and the wiring diagram colors are the same.

 

But my Wiring Harness is not even close to what it should be, nor is the carb if the 77 used the same color coding (which I suspect is Yes.)

 

From the Service Manuals:

 

LW, WL, YR  Manual

LW, WL, BW  Auto

 

My harness (round black rubber or barrel connectors) is:

 

L, B, BY   NOTE;  Wires functions unidentified - this is the Question

 

My 77 carb is 

 

L, R, W

 

Note:  My harness wires are a subconnector and only about 8" long.  They plug into the engine compartment harness with a 4-pin barrel connector.

 

Regarding Connector Types:

 

Harness:  All (3) are Female Pin

 

Carb:  All are Male Pin EXCEPT Red:  it is Male Spade

 

So they don't match either, but then its a 77 carb on a 74 620.

 

Thanks in advance,

Tom

[bonvo]

pics would help but either way your doing some electrival work

[datsunaholic]

What are the wire colors on the other side of the barrel connector?  Someone may have changed the pigtail end of the plug.

 

On a '74, the carb wiring comes from the firewall harness.  Later years (75+) it comes from the harness by the coil.  So ensure that's what you're looking at.

 

In any case, the Idle Cut (anti-dieseling solenoid) will be live with the ignition on.  The choke heater will only be live with the engine running (only when the alternator is charging).  The BCDD is controlled by a relay and a speed switch in the speedometer in M/T versions and via the inhibit switch in A/T versions.

[Cardinal Grammeter]

Thanks datsunaholic. 

 

My pigtail comes off the firewall harness.  But since the round black rubber connectors are only used in 74, I'm guessing I have the right one.  (Of course could be a pigtaile from another 74 model.  But seriously, the monkeys that worked on this 620 basically stripped everything off they could.  The electric choke on the plywood 1-bbl was hooked up with a jumper from the coil.  Yep.  Real Geniuses.)

 

I just realized the shop manual shows the pin outs  so I could do it that way.

 

But considering how butchered things are, I better verify the operation as you described.

Thanks

Tom

[Cardinal Grammeter]

Datsunaholic!

 

As you suspected, the main harness has the proper colors!

 

Wonder why the pigtail extension was completely different?

 

And wonder why they didn't use unique connectors for the 3 wires coming off the carb - all same gender pins really is asking for trouble.

 

I figure this thread is solved!!

 

Thanks

Tom