Injector pulse is evading me...1978 280Z

[280z_new2me]

Hello,

My first post...lurking in the background since this spring and a subscriber for several months now.  My son and I agreed to restore a car...he took the interior and body, leaving me with getting an engine running last inspected in 1997.  Getting the engine going has been a WIP since this spring/summer.  I'd like to hope that I'm close and want to run by where I'm at...a bit stuck actually, hoping it's not the ECU.

Here's a summary: I've got fire (new plugs, wires, distributer cap) verified spark on the plugs.  Fuel injectors were sent off for cleaning and are re-installed. New EFI connectors soldered in. Coils tested good with 9v battery.  New battery and FP.  Used DeToxit on EFI harness connectors.  Went through troubleshooting steps in the EF part of FSM for "Doesn't start", confirming power (12.48v) and grounds, (static) signal from "-" coil, etc...all passed 1-(3,5-8), 2-(1-3), 3(1, 3).  

I can't understand why the injectors won't pulse.  I tapped on the "-" of the coil (ignition "on") to ground multiple times and can hear the injectors cycling.  Is there another test? I have a NOID light confirming they aren't pulsing.  I'm afraid it's pointing to a bad ECU but would like to get some feedback and suggestions as to what I can try next.

My paranoia makes me ask if having the dash pulled out, so instrument panel disconnected, could cause this?  I understand there's many inputs into the ECU to adjust the pulse width...I'd be happy with just a pulse at this point.

Thank you for any suggestions and ideas to try!

ZT 

 

 

[Zed Head]

9 minutes ago, 280z_new2me said:

instrument panel disconnected, could cause this? 

I discovered this exact problem on a completely stock 1978 parts car.  It would not actuate the injectors if the tachometer was disconnected.  Apparently, some 280Z's will and some won't.  I confirmed it a few different times on the 78 and my 1976 car.  You'll find people that say theirs starts just fine without the tach and others like me who say it won't.  After I switched to a different ignition system it didn't matter if the tach was connected or not it always started.  So it seems like the ECU is very sensitive to what's happening on Pin 1.

Short answer - you're probably right and it will probably start right up if you connect the tachometer.  It's probably not the ECU.  You did all of the right testing too.  Good luck.

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Edited December 3, 2023 by Zed Head
+78

[280z_new2me]

Hi Zed Head, many thanks for the quick response.  I'll try removing the tach from the dash and plugging it in.  Dash was taken out to try and improve its own sad state of affairs.  I'll report back what I find.

[280z_new2me]

Hi Zed Head, you were correct!  I  temporarily placed the dash close enough to connect the three cables under the glove compartment.  My noid light was nice and bright as she cranked with spark plugs removed.  I need to replace the water pump or I would've fired her up.  The seal is leaking quite a bit and I have the pump so it's off to the next item.  

Thanks again...much appreciated!

ZT

[Zed Head]

Thanks for the follow-up.  These weird problems need examples.  Good luck with the project, you're at the right Z forum.