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i have a 76 280z.if the fuel regulator is bad will the car run rich or lean.thanks a head of time
 

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depends on what position the regulator is stuck in...could lean or rich. if stuck open it would run lean if stuck closed would run rich
 

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Just my 2 cents worth

I have heard two professional Z mechanics (one I've used and the guy on the ZTherapy fuel injection video) state that fuel pressure regulators hardly ever go bad, yet they are the first thing everybody (including me) replaces when the car doesn't run right. These mechanics both also state that 95% of the time, the problem is either electrical or a vacuum leak. If you want to spend $60 for a new one, go ahead, but maybe you should try cleaning contacts and testing various sensors before you do.
 

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Put a fuel pressure gauge between the fuel filter and the fuel rail.

If it reads 32 PSI at idle and 32 PSI when you rev the engine above 2000 RPM it will be correct at idle and lean under WOT.

If it read 42 PSI at idle and 42 PSI when you rev the engine above 2000 RPM it will be rich at idle and correct under WOT.

If it reads 32 PSI at idle and you disconnect the vacuum line going to the FPR the pressure should go to 42 PSI. If it does not you have a problem.

If you put a vacuum pump on the FPR and increase the vacuum to 16 inches the pressure should drop to 32 PSI. If it does not you have a problem.

Put a vacuum gauge on the line that goes to the FPR you should have at least 16 inches of vacuum at idle and the gauge should be steady.

If you have less than 16 inches of vacuum at idle AND the FPR is working correctly the engine will run rich.

Wayne Monteath
Masham, Quebec.
 

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true fuel pressure regulators seldom go bad. but most will stick shut fuel pressure will be in the 50 to 60 range and pump will make a noticable whine (pressure relief valve in pump). the other failure is the diapham to rupture in which case so much fuel will be sucked down the vacume hose as to almost instantly flood engine and drown plugs to point of having to be clean before they can work.
 
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