please help really bad day

[Zed Head]

Yes, that's the one. Virto's picture might be of an earlier link, the white piece is actually just a plastic support piece, the wire itself has green insulation. They went to two wires in 77 or 78. It's shown on page BE-6 of the FSM, although the picture's not great.

[EuroDat]

Do you have a battery frame insulator on the bolt to the body. I didnt have one and my frame kept coming loose. Now it has one, its never came loose since.

Banzai Motorworks

You can pick up a fusable link through Courtesy Nissan. The part number is 24022-U8700, but its superseded by 24022-N7600 and costs around $7.50, depending which one you choose. Both are available through Courtesy. I am not sure what the difference is, but mine (N76) has white treminals, a green wire plus a nylon wire. The nylon wire holds it in place when the link blows. I have seen them on E-bay without the nylon, but they are probably not OEM.

FUSIBLE LI :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

You can see it in the 280z parts manual, but its poor detail. See Pos# 45 in the link.

Datsun 280Z Wiring (Engine Room) (From Aug.-'76)

Gooluck

Chas

[scotts pearl]

thanks guys. i checked the link and it checks good. i do not here the fuel pump running. any ideas?

[superlen]

Scott,

You're on the right track by making sure the fuel pump is working. Do you normally here it when you start up? Sometimes the sound of the starter covers it up. Don't worry about the ECU yet. It doesn't actually control the fuel pump at all. It may actually be dead, but I don't think it's likely.

The fuel pump can be turned on by two things:

1. A switch in the Air Flow Meter that turns on anytime the flap is being pushed by air (or your finger)

2. turning the ignition switch to START. Our pumps don't do a timed prime when you just turn on the ignition.

The easiest way to test is to pop the hood and pull the small solenoid wire going to your starter solenoid. It just plugs on so no tools needed. Now try to start the car with the key. You wont here the car crank as you just disconnected the starter solenoid, but the start signal should hit the FI relay and cause it to power the pump. You should definitely hear the fuel pump now with the engine quiet.

Also look for mechanical issues from the event (assuming your battery was sliding around hitting things), and melted ground wires. When a battery + post grounds the frame the current is going to flow through the easiest path from the + post to the - post. Hopefully that is from the + post into the frame (where it just touched) through the frame to the nearest/best ground strap, into the ground strap, back to the - post. Notice, there are no fusible links/fuses anywhere in that path. You shorted *before* them. (right at the post) That's why you saw smoke instead of heard "poof" and then nothing as a fuse blew. The insulation on your wires was melting from the heat.

The good thing is that this current path doesn't go through *ANY* components, not a switch, not a light bulb, not an ECU, so a massive current event didn't go through those. (Voltage spike is another critter I'll ignore for now).

Check all your ground wires in the engine compartment and look for melted insulation and verify that they are still in fact grounded. I don't have a schematic handy, but I believe there is one specific ground wire for the EFI system up there near the battery.

[EuroDat]

It could be your fuel injection relay. It controls the power supply from the fusable link.

There is a colour diagram for the 280Z 1977 model which does have some differences, but it is clear to follow.

If you follow the wire from the fusable link, it goes to the relay (70) and comes out (43 injectors, 10 CPU & 39 AFM contact switch). The power supply to the fuel pump is (74) in the relay terminal block. Check if you are getting power to the relay and work on from there. Good as any place to start.

http://www.classiczcars.com/forums/electrical-s30/13131-color-wiring-diagram-280z.html

Chas

[Captain Obvious]

In theory, shorting the battery post right to ground through the hold-down bracket should not have put any current through any of the fuses or fusible links at all. The loop would be:

• positive battery post to the body through the hold down bracket
  
• body into the harnesses through all the ground wires connected to the body
  
• the ground wires back to the battery negative post through the negative batt cable and/or the FI ground connection
  

Of the two ways to get back to the battery negative post the negative FI connection is clearly the weaker link. I'd start there and at the body to block ground tie connections.

I bet you burned up a ground wire or one of your FI components that connects to ground. If stuff got hot enough that you got smoke, there should be visible damage somewhere. Look at the smaller ground wire off the battery that goes to the FI system. If it's not there, you should probably seek the assistance of someone in your area who really really knows the FI system because it's probably gonna be a tricky hunt.

I didn't look hard, but quick scan shows the FI main relay, thermotime, fuel pump relay, fuel pump control relay all connect to ground.

On edit... I see that lenny types faster than I do!

Edited August 10, 2013 by Captain Obvious
superlen types faster than I do

[scotts pearl]

thanks guys. problem solved !!!!. fusible links did burn. they saved me whew.

you guys are the spocks of z cars. this is a great site. i did find the problem with battery bracket. the bolt on the firewall is missing just as euro dat said. will order new links and battery insulator.

[Captain Obvious]

All that stuff I said about big current not flowing through the fusible links? Forget all that... I bet one or more of your fusible links fried. You should double check them to be sure.

(Glad you found it!!)

[scotts pearl]

one fusible link did fry. one of the green as zed spoke of.

[superlen]

Scott,

Glad you're up and going again. I'm still wondering what path the current took to get though the links??? Captain I both typed the same thing. (Wrong of course. ) I may need to refresh on the schematics and wiring of those links, is one or more of the links in the ground path?

Lenny

[scotts pearl]

i really dont know how it took path. all i know is when the car shorted out I did pull the ground and positive quickly to prevent fire. did leave burn mark on my hands.

i do have my stereo hooked directly to battery for memory and it blew an inline fuse there as well.

[scotts pearl]

one more thing all guages went crazy. some went all the way over and some down. ????????????. i see what you guys meen how could it ground somewhere else othe than the battery bracket.