Update: My 280Z will not start. I am getting 0 PSIG on the fuel pressure gauge on the fuel oil supply line. I was able to source a replacement fuel damper and plumbed up everything. Troubleshooting per the Fuel Injection and Factory Service Manual led me to find the following:

• All wiring connections are as intended - I did not find any plugs or harnesses disconnected.

• The fuel pump is not getting power when I start the car.

• No voltage is present at the fuel pump across the power and ground terminals when the key is in the "On" position.

• No voltage is present at the wiring harness under the passenger seat at the green wire and black ground when the key is in the "On" position.

• The fuel pump relay clicks when I try to start the car.

• The fuel pump operates when I run a direct line from the positive battery terminal to the pump.

• All of troubleshooting checks from the "Engine won't Start" section of the Fuel Injection Bible pass and my efforts lead to quote "try a different ECU."

• I was able to source a second ECU on eBay, but it yields the same result.

• My taillights and license plate lights do not work (not getting power).

• Running a separate ground wire from the fuel pump negative terminal to a chassis ground does not resolve the no starting condition.

Based on my findings above, I am not sure what my issue is or to diagnose why I am not getting any power to the pump. Anyone have a similar problem and can diagnose?

I thought maybe it was a bad ground, but wouldn't the separate ground wire have resolved the problem? From what I understand, the main ground that the fuel pump, taillights, etc. are connected to requires removal of the gas tank to access. I was hoping to avoid this, but if it is my next step, so be it.

Also, when the previous damper failed, it did drip gasoline on to the pump and terminals. This is because on 1976 280Zs, the damper is above the pump and the whole kit (damper, pump, hoses, wiring) is mounted to an L shaped bracket that is mounted with three screws to the chassis. This was changed in 1977 and 1978 models to a flat plate that mounts to the chassis but places the damper and pump side-by-side. I'm guessing this was an improvement that would have reduced the possibility of a failed damper leaking fuel onto the pump. Could that wetting of the pump terminals have ruined my ground wire or power wire to the pump?

How likely is it that my remanufactured aftermarket ECU and the eBay replacement (which was started to be from a 1976 2+2 4 speed, just like mine) are both bad and presenting the same exact issue?

Edited April 27Apr 27 by Paulytunes

Sounds like your fuel pump relay is bad. Send me a pm.

On 4/26/2025 at 11:39 PM, Yarb said:

Sounds like your fuel pump relay is bad. Send me a pm.

Thank You!!! I was finally able to source a Bosch plastic housing replacement relay on eBay marketed as a VW part. It arrived on Tuesday, and I installed it today. I knew that was it when I turned the key and heard the hum of fuel pump. Once I added some fresh fuel to the tank, I turned the key, watched the fuel pressure gauge climb up to 36 PSIG, and the L28 started and ran! I do need to still do some troubleshooting and fix the backfiring and high idle, but those seem like much smaller challenges now that I have a running car again. Apologies to my neighbors, I think the whole community heard my hollers of joy and elation when the Z fired up this afternoon! A small victory, but a much-needed win for me today with all that has been going on at work.

Edited 12 hours ago12 hr by Paulytunes