1976 280Z Fuel Issues Troubleshooting

[Zed Head]

25 minutes ago, Paulytunes said:

When I unscrewed it and examined it, I noticed a qr code. When I scanned it, I am sent to a website that no longer exists.  The website was Installapart.com. It appears that Installapart is no longer in business.

I found your Ford doppelganger from 2021.

https://www.ford-trucks.com/forums/1656335-91-f150-losing-spark-intermittently.html

"There is nothing I could find on the Computer that indicated where it came from or what calibration it is for. The only thing it had was a QR code that directed me to a site called "installapart" but the site itself looked closed."

[Paulytunes]

10 hours ago, SteveJ said:

You can see the site using the internet wayback machine: https://web.archive.org/web/20180307072216/http://www.installapart.com/

Thanks!  This was certainly an unexpected and unfortunate discovery.  I wasn't able to track down how to troubleshoot the ECU - those pages are probably long gone or that institutional knowledge died when the company went 6 feet under.  I have had nothing but trouble with aftermarket parts that one of the PO's installed - first the fuel pump now this.  I guess I am at a crossroads - Do I try to source a working 1976 Datsun 280Z ECU, go down the Resto mod path of installing a FAST ECU or other replacement system, or continue to struggle and troubleshoot with what I have (even though it may be an exercise in futility)?    

[Paulytunes]

10 hours ago, Zed Head said:

I found your Ford doppelganger from 2021.

https://www.ford-trucks.com/forums/1656335-91-f150-losing-spark-intermittently.html

"There is nothing I could find on the Computer that indicated where it came from or what calibration it is for. The only thing it had was a QR code that directed me to a site called "installapart" but the site itself looked closed."

Zed Head - that is Interesting, thanks for finding that site.  The OP never does say what he did with the ECU.  

[Patcon]

My 2 cents (45 cents)

If I owned a 280z, when I started having problems with the factory EFI system, I would ditch it and go to a more modern more easily tuned system

[siteunseen]

2 hours ago, Patcon said:

My 2 cents (45 cents)

If I owned a 280z, when I started having problems with the factory EFI system, I would ditch it and go to a more modern more easily tuned system

Don't let your wife read that!  

https://atlanticz.ca/zclub/techtips/  aka "Blue's Tech Tips" and this forum is all I needed and I don't have any cents.

 

 

 

[Paulytunes]

So after much trial, error, troubleshooting, and going through the Fuel Injection Bible and FSM, I was able to get my 280Z running again.  The issues I have now:

1. I stupidly broke the plastic nipple on the stall dashpot while connecting the thermostat sensors and wiring:
2.  Idling is pretty high, around 2000rpm at cold start.  Occasionally, it will adjust down to 700 to 800 rpm and will sometimes stall.  Other times it will stay at 2000 rpm, unless I drive it and can force the RPMs lower with the gearing.  When I take it out of gear, it shoots right back up to 2000 rpm.  May be due to the temps here, which were between 55 and 60 degrees F today.  

I was able to temporarily fix the dashpot and reconnect the vacuum hose to it using a smaller diameter tube to insert into the part of the intact plastic and the vacuum hose until I can source a new dashpot assembly.  I'll continue to diagnose the high idling and see if this is due to something I am overlooking or a symptom of my rebuilt ECU not performing up to OEM standards.    

[Zed Head]

That nipple shouldn't have a vacuum source connected to it, it should be open to the air.  It's a common mistake.  Don't know why Nissan designed it that way.

A common problem with the pre-77 throttle bodies is that the blade gets gummed up and sticks open.  You might check that.  Next time it hangs at 2000 pull up on the throttle pedal with your toe or open the hood and press the linkage closed.

Another possibility is that the return spring rusted and broke.  It's hidden away, low and behind the TB.  Can't remember if you already addressed that possibility.

Finally, the other "hanging high" problem is caused by the BCDD.

 

Here's a drawing of the dashpot with no hose connected.

[Paulytunes]

15 minutes ago, Zed Head said:

That nipple shouldn't have a vacuum source connected to it, it should be open to the air.  It's a common mistake.  Don't know why Nissan designed it that way.

A common problem with the pre-77 throttle bodies is that the blade gets gummed up and sticks open.  You might check that.  Next time it hangs at 2000 pull up on the throttle pedal with your toe or open the hood and press the linkage closed.

Another possibility is that the return spring rusted and broke.  It's hidden away, low and behind the TB.  Can't remember if you already addressed that possibility.

Finally, the other "hanging high" problem is caused by the BCDD.

 

Here's a drawing of the dashpot with no hose connected.

Thanks, I'll look into that.  So should that vacuum house then be open to the air or connect to something else that I am not seeing?  There's a three way tee, which was always connected to the dashpot nipple, a vacuum port on the bottom of the AFM, and also to the charcoal canister vent on the other side of the engine bay. 

The dashpot connection does indeed seem to be common, many other L28 engine photos online show it connected.  

[Zed Head]

The three way T should go to the ported vacuum on the TB, the charcoal canister, and the distributor vacuum advance mechanism.

Here's a good place to browse pictures.

https://bringatrailer.com/search/?s=1976+280z

https://bringatrailer.com/listing/1976-datsun-280z-88/