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Low Fuel Pressure 78 280Z


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My 78 280Z has only 15lbs (steady) of fuel pressure. It has been setting for several years since I bought it and was running rough.  I had the injectors rebuilt, replaced the fuel pump, the pressure regulator, both new from Nissan along with all rubber hoses, belts, new plugs, wires cap, rotor,  valve adjustment, etc.  Fuel pressure has not improved.  Is my next step replacing the fuel damper?  I have never had a problem with a damper in my decades of playing with these cars. 

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Filter?  Don't see it listed.

 

You could bypass the damper before replacing it, if you think it's an obstruction.  It's purpose is just to reduce pressure pulses, to make things last longer, and probably make things quieter.  But the engine will run fine without it.

 

But, really, even with an obstruction, your pump should build pressure, if you test it without the engine running.  The FPR is just a pressure relief valve.  It won't open until pressure is reached.  Are you sure you got an EFI pump?  Maybe you got a carb pump.

 

Also - bad gauge.

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NewZed, I suspect the pump isn't doing what I need.  I purchased it locally from Nissan parts dept so who knows what I have. I will check it's output pressure before I do anything else.  Although it's "new", I purchased it about 18 months ago so there will be no exchange from Nissan.  Thank you for your help. 

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You can dead-head the line and should get at most about 60 psi.  The Nissan pumps have an internal relief valve.  If you want to test it just put a gauge at the end of the output line close to the pump, crank the hose clamps down and apply some power. 

 

It might be something as simple as a piece of old hose stuck in your new regulator.  Best to check the pump alone before assuming too much.

 

Forgot to say, the inlet needs to be unobstructed also.  If you had the tank sealed it's not uncommon to end up blocking the inlet to the pump.

 

And - gauge on the wrong line.  The return line, maybe.  It happens.

Edited by NewZed
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