Fuel pressure reg issues on late 260z 2+2

[voslachlan]

Hi all,

Our '76 260z 2+2 donor car came with an electric pump (Goss GE002 - very little info out there and likely not standard) and a powered fuel pressure regulator (Nikki SB-10, seems to match with other photos on the web but can't find any documentation about it) with both in a hanger behind the driver's side rear wheel arch. We've been trying to get it reliably pumping fuel with the exisiting setup (didn't work at first, replaced pump but issue was blocked connector, now back to previous pump) but are at a standstill. When the fuel hanger is sitting on the ground, fuel reaches the mechanical pump at the pump with no issues, whether the fuel pressure reg is plugged in or not. When the hanger is lifted up into position, fuel comes through only with the pressure reg unplugged. And with a filter inline as per standard, it will only work if the hanger is low, it's almost like the pump can't draw through the filter unless there is a siphoning effect out of the tank. 

 

Since we are just trying to get it on the road for now and have plans for EFI down the road, can anyone provide info on the mystery pressure reg and how it's supposed to work? Why does it need power? Is it safe for the SU carbs to run the Goss fuel pump with no regulation directly into the mechanical pump and into the carbs? Why an electric fuel pump by the tank in the first place?

 

Have attached a photo of the hanger as removed from the car (just with replaced connectors)

 

Cheers,

Lachlan

Edited June 19, 2023 by voslachlan

[voslachlan]

Update that’s hopefully helpful for people with a similar fuel setup in their S30’s:

I pulled apart the Nikki pressure reg, and the mechanism instead seems to be pretty standard affair, with a sprung piston with a rubber insert on the tip acting as a diaphragm over an orifice on the inlet. However, the 12V in goes to a coil/electromagnet that when powered, pulls the piston up - effectively bypassing the spring so it will always flow fuel through the regulator. My guess is this is for safety, to keep fuel at the rear of the car in case it gets in an accident with ignition still on for example, since currently the fuel pump runs as soon as the ignition is on. However, this is a guess and I’ve still got some experimenting to do to figure out when the pressure reg 12V is switched on. 

[AndBir]

24 minutes ago, voslachlan said:

figure out when the pressure reg 12V is switched on

I think this will be a fuel cut-off that requires has relays (ignition to be in the on position and power from the alternator) to be active for it to be open.

https://www.classiczcars.com/forums/topic/66277-brand-new-260z-owner-looking-for-fuel-pump-relay-help-c/?do=findComment&comment=634704

Edited June 26, 2023 by AndBir

[voslachlan]

Cheers for that link, very helpful. Seems like the pressure regulator in our setup slightly complicated things compared to that more standard setup, but likely still lots of similarities. Currently have the alternator unplugged due to a missing voltage regulator so will check if the behaviour matches that post when it’s all connected up.