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mikemac44

Low fuel pressure.car runs better

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Hi.i have a nissan fairlady 1977(260z 2+2)it was a 2.0lt efi L20e.just getting it running after full restoration.I have completed a L28e turbo swap.running a 280zx turbo system including dropping resistor from a 1981 car.motor fully rebuilt.new airflow meter.distributor cas.new injectors for a turbo.(ohms of 4.8).new fuel pump and adjustable fuel pressure reg.my queston is.with car idling hot,if i set fuel pressure at 35 psi car starts and runs abit lumpy,running rich?.if i drop fuel pressure to approx 8 psi it runs a heap better.i have tried another fuel pressure reg and guage incase readings were wrong.i have not driven car yet on the road as no windscreens etc.but it revs freely at this low psi reading and does not peter out.I have replaced fuel pump with new high volume pump and kept original fuel damper.only thing i can think of is the injector flow rate?the new injectors are supposed to be for a 280zx turbo.they outwardly look the same and have correct impedence.Does anyone have any suggestions?thanks in advance.

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Hi,thanks for your reply,yes I went through all pin outs  xenon z workshop manual and even tried using a resistor wheel to change coolant sensor resistance to see if that made and difference,which it did but didnt change fuel pressure,will triple check again on weekend,cheers

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When people say they did "all" of the tests, it usually comes out later that they skipped a few or didn't actually measure numbers, just continuity.  Just saying, you have to be rigorous and detailed when you work on these systems.  Good accurate numbers measured at the right times.  For example, 35 psi on a running engine is too high, if you set the pressure while the engine is running.  Besides that, if you don't show the numbers you got then people out here can't really offer good advice.  Everybody says that they did everything right, so there's no wrong to fix.  Also, 4.8 ohms is too high for injector resistance, so it makes you wonder where you got your specs.  Although it alone wouldn't cause your problem.

8 psi is really low fuel pressure though.  A fairly common problem is a blown FPR diaphragm.  Of course, you'd have to have two bad ones since you tried two and got the same results.

Just trying to help.  Need more details.  Are there numbers on the injectors, for example?  That would be a clue.

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