N/A Hard Start Conditions

[MarkerZ32]

So after driving my Z for a year with no problems (I pulled the original blown VG and replaced it with a used J30 V6) I have developed a few hard start issues.

At first I had an extended crank that was getting longer and longer but would run fine once started. Finally one day the car died maybe 3 minutes after starting and driving. So I pulled her back home and decided to try tapping on the fuel pump cover for laughs. Funny story, she fired right up! But I knew I was on borrowed time and ordered a Delphi pump. While waiting for the new unit to arrive the extended crank issue came back but didn't get worse. Fuel pressure was 10psi Key on engine off, shoots up to 40psi when cranking, then just 42psi at idle, pressure drops with regulator unplugged but I forget... maybe to 32psi.

Since replacing the pump, I'm now getting the following issues

In the morning, I initially get an extended crank. But it helps sometimes if I give it a few turns, cycle the key off, then cranks and starts normally.

After I get it started and running, it will always start right up if I shut it down, hot or cold.

But if I leave her parked for maybe 10 minutes, I get an extended crank condition and it's really hard to start. Sounds like it's firing up but dies immediately if I let off the key. I have to hold the key and crank until it sputters up and starts running again. Then continues to run fine. Plenty of power and little to no hesitation.

I haven't checked my fuel pressure since replacing the pump, but I will do so tomorrow and post my results.

[nissanfreak12]

Sounds like the new pump is not holding the pressure like it is supposed to. Most pumps have an anti-drain valve on them to prevent fuel going back into the tank.

Was this a new pump or new to you pump?
What brand was it?

[MarkerZ32]

It's a new Delphi pump. But I did notice one of the wires (a yellow one I think) was exposed and kinda corroded. Maybe I'm getting some high resistance?

[MarkerZ32]

Okay so after a few more hours of research I've come to the conclusion that I have an issue with my fuel pump control module and some exposed wiring. I won't be fixing this until the end of July, when I do my second engine pull. But my remedy will be to supply fused power (30A) directly to the pump from the existing pump relay circuit. I will also install a redundant pressure regulator with a bleed function to allow for over-pressure fuel to return back to the tank, preventing the pump from overloading itself, the circuit and the stock pressure regulator.

Thoughts?

[DCaff300ZX]

A worthwhile check is to see if the PTU harness connectors have corrosion, your issue sounds very close to one I've had twice and was the problem before being replaced with upgraded weatherproof replacement from Z1.
Worth a check!