Another EFI Injector Pulse thread

[Datsun&Goliath]

Hey Everybody, 

A few months ago I acquired myself a rust bucket 76' 280z (mainly for parts and drivetrain) I want to get the engine running to confirm that it is worthy of holding onto. 

Somehow I cannot get the injectors to pulse. The car fires right up when hit with ether and will run as long as ether is supplied. BEFORE everyone goes ahead and says it I DO have the EFI BIBLE and have gone through it best of my ability to follow the testing suggestions. 

What I've done so far: 

Pulled all 6 injectors, tested that they open and produce fuel, not clogged.

Have a NEW Fuel pump hooked right up to the fuel line. Connected back at the tank so that the pump activates when cranking. 

Checked all four fusible links on passenger side of car  with volt meter. All seem good. 

Ran a Negative jumper from coil to pin 1 in the ecu. To eliminate bad ground wiring in harness.  

Checked pin 10, 20 for fuel pump circuit and relay. 

Injectors have a current, they are lacking their ground from the ecu when I crank. 

Did a pulse test ( ran a negative to the - terminal of coil, with key On grounded it on the body quickly to check for pulse) got all six injectors to pulse a few times. They only pulsed a couple times and then this didnt work anymore.) 

From here I'm not sure what else to do. I read that maybe I should check out the dropping resistors? How would I test these? Also how would I test the EFI Relay? 

 

Thanks in advance

[Zed Head]

I've found in the past that the ECU is sensitive to the quality of the Pin 1 signal.  I can't really say how, but I do know that I had two situations where the engine would not start when the tachometer was disconnected even though the path to Pin 1 was still intact.  Reconnected the tachometer, which is on a branch of that circuit, and it was back to normal.  The fact that you got the injectors to fire by grounding coil negative shows that the ECU "sees" what it should from the coil negative but it's not liking the signal.

But I've also had an engine on a stand with no tachometer start and run using a separate EFI harness.  In that case I ran a wire through the 2.3 kOhm resistor on the tach circuit to ground.  My theory was that the ECU needs that constant high resistance coil ground circuit to operate right.

You might try getting the tachometer circuit to normal, if it's not.  Or even add a capacitor or a high resistance path to ground on the Pin 1 circuit.  I've fixed a bad tachometer by adding a condenser.  It's pseudo-voodoo 'cause I don't know why it works but it won't hurt.

[Zed Head]

The tachometer circuit resistor is by the realy area/fuse box wiring.  It's a lump inside the harness, with a female and male bullet connector.  Dig it out and branch your pin 1 wire to ground through that resistor.

[JSM]

Also does your tach bounce a little when cranking?  Also did you check power is getting to the dropping resistors?  It looks like each plug gets power from the EFI relay  (Pin 43).

http://www.atlanticz.ca/zclub/techtips/wiringdiagrams/76_280z_wiring.pdf

Edited January 31, 2017 by JSM

[Datsun&Goliath]

Ill give these all a go tonight! Thanks!

 

[Datsun&Goliath]

I am also going to go through the entire test cycle again in the EFI bible, keep you all posted. 

[JSM]

On 1/31/2017 at 6:42 PM, Datsun&Goliath said:

I am also going to go through the entire test cycle again in the EFI bible, keep you all posted. 

Any luck?