Since you replaced some hoses you should move the gauge back to right in front of the rail and measure there.  You're narrowing things down.  Zero pressure on the return line might be good.  seems like you would have seen a pound or two.  If you still get high pressure from right in front of the rail, then the blockage is in the rail, or the FPR, or the line to the FPR, or the return line between the FPR and where you have the gauge now.

 

Put the FPG right before the rail. Getting 51-52 psi at cold start. So from the gauge to the FPR there might be blockage or FPR to what point does the pressure stop on return?

 

Also what would be easiest way to clear blockage?

 

1977 280Z

EL Paso TX

If you want to narrow things down further, disconnect the FPR at its exit.  That is a likely spot for misalignment.  Since the FPR has two entry points it seems most likely that the single exit is clogged than both entrances.

If you run a hose from the exit of the FPR in to a can and still get high pressure then the FPR itself is a likely cause.  

The FPR is just a pressure relief valve.  When pressure rises to its setpoint it lets fuel exit and go back to the tank.

 

My FPR only has 3 connections


1977 280Z
EL Paso TX

Car running with FPR return disconnected I still get 50psi. Have return just emptying into red gas can.


1977 280Z
EL Paso TX

You must have a 78 rail and FPR.   So that takes out the connections between the rail pieces as the problem source, it's a one piece rail.

There's only one connection left.  If you still get 50 psi from that spot there's something clogging the rail.  If pressure drops the problem is in the FPR. 

That's one crusty looking FPR.

You must have a 78 rail and FPR.   So that takes out the connections between the rail pieces as the problem source, it's a one piece rail.
There's only one connection left.  If you still get 50 psi from that spot there's something clogging the rail.  If pressure drops the problem is in the FPR. 
That's one crusty looking FPR.

So disconnect hose ware you put the red box and let gas flow out into a container?

would I still leave the pressure regulator between filter and rail?


1977 280Z
EL Paso TX

If you disconnect the hose there, there will be no fuel flowing through the FPR.  Take the FPR out of the flow path to see if it is clogged.  You'll have fuel flowing only through the rail.

If you disconnect the hose there, there will be no fuel flowing through the FPR.  Take the FPR out of the flow path to see if it is clogged.  You'll have fuel flowing only through the rail.

 

Ok I will test like that.

 

Are there any good priced FPR that I can get besides the ones from zcarsource, zcardepot, etc. they all seem to run in the $100+ range.

 

Thank you for all the help.

 

 

1977 280Z

EL Paso TX

I may have one. I would have to look

53 minutes ago, Patcon said:

I may have one. I would have to look

cool if you do happen to have one let me know,  i also have an old 280zx that was a parts car for a previous zx.  will need to go and see if FPR can be salvaged.   car has been siting for a very long time.  Is there a way to clean them out?  I assuming i would just hook it up and let gas run through it.   i also have a spare fuel pump i could rig together to let the gas flow through the FPR.

Removed the FPR got no fuel pressure. I did have another FPR on old ZX. Ran some gas through it and Fuel pressure is at 32psi. So my original FPR must have been gunked up. The new salvaged FPR might eventually give out as well.

What I did notice which I don’t think had happened before is I would here my relay clicking. I had the oil pressure disconnected so fuel pump would just run and than relay started clicking on and off. Is that normal?

With oil pressure connected and car running I didn’t here the Relay clicking.

Another thing i did was moved the clear fuel filter. It was between fuel pump and engine. It took the place of the fuel damper. It’s now between the gas tank and fuel pump.

So now I just have a hose from fuel pump out to fuel line.


1977 280Z
EL Paso TX