78 280Z - no injector pulse

[kelley0352@att.net]

14 minutes ago, kelley0352@att.net said:

@ 6.2-6.3 with a volt meter & with a 12v test light

I am sorry, my mistake at the findings . the voltage at the injector plugs are 12v, the ohm readings from the drop resistor are 6.2 & 6.3

[kelley0352@att.net]

12 minutes ago, Zed Head said:

If you take a wire and ground pins 14, 15, 30, 31, 32, or 33,  with the key on, you should hear the injectors click.  At least you'll know that most of the circuit and power supply is complete.  Use your noid light and you can avoid accidental short circuits.  Plus you'll see the light flash as the injector clicks.

 

[kelley0352@att.net]

Just now, kelley0352@att.net said:

Yes, #14 is #4 injector,  #15 is # 1 injector, #30,31,32,33 are injectors 5,6,3,&2

 

[Zed Head]

Working on the EFI system is boring for people looking for instant results.  But kind of satisfying for people who like to see long lists of measurements.  That's why Nissan published the "Bible".    Get a piece of paper and start collecting numbers.

[kelley0352@att.net]

Just now, kelley0352@att.net said:

Just for the groups information, the drop resistors replacement parts are available through any napa dealer. 

I already did start collecting #'s so now what ?

 

[Zed Head]

With the key on if you complete the circuit to ground on those pins and the injectors don't click then they will never click via the ECU.  That's all that the ECU does, is ground those pins.  Don't hold it to ground too long you'll fill the engine with fuel.  Just a tap to ground will tell you if it's working.

[Zed Head]

1 minute ago, kelley0352@att.net said:

I already did start collecting #'s so now what ?

Post the numbers on the site so we can see them, and we know which tests that you did.

Edited July 18, 2020 by Zed Head

[Zed Head]

10 hours ago, kelley0352@att.net said:

 I have replaced ECU, 

Where did you get the ECU?  Is it new?

[kelley0352@att.net]

I pulled the ECU out of a running 1978 Datsun 280 Z and put the other one back into another running 280Z and it is working just fine in that car.

I have my list of all the pins from 1 to 35 so I know what every pin goes to.

This is why it is so frustrating; I have replaced anything on the car that could cause the failure , from the ECU to the Thermo time switch and have not resolved the problem. I have traded out the transistor ignition box (that I can rebuild) and the throttle positioning switch. The only thing I have not replaced is the air flow box.

Edited July 18, 2020 by kelley0352@att.net
clarification

[Zed Head]

That's the beauty of the wiring diagram of the system.  You can do little tricks like grounding the injectors to see if the circuit is complete.

There's another trick you can do by grounding the coil negative pin.  But, just like taking measurements, there's a certain sequence that needs to be followed.  Confirm one thing before moving on to the next.

[kelley0352@att.net]

5 minutes ago, Zed Head said:

That's the beauty of the wiring diagram of the system.  You can do little tricks like grounding the injectors to see if the circuit is complete.

There's another trick you can do by grounding the coil negative pin.  But, just like taking measurements, there's a certain sequence that needs to be followed.  Confirm one thing before moving on to the next.

I have been going through the process of elimination for 3 weeks now. I went over to my running Z car, (that I have 3) and touched the 12v test light to the neg side of the coil & now it will not start either because of no noid light, (signal to the injectors) and I do not know why this would happen from a no voltage test light! Frustrating!

[Zed Head]

5 minutes ago, kelley0352@att.net said:

 touched the 12v test light to the neg side of the coil

This does not really mean anything.  You touched the negative post of the coil?  Was the key on?  Did the test light flash?  Was the engine running when you did that?

The details will have the clues.  You're just not providing enough information.