BlueZ31 Posted November 8, 2011 Share Posted November 8, 2011 Hey all, I've recently replaced my stock N/A '87 fuel pump with a walbro 255lph, along with a new fuel filter and fuel pressure regulator. Before these changes the car had 30psi of fuel pressure measured after the fuel filter, but would drop to below that when the pedal was depressed. After these changes, the same thing occurs. The FSM states that it should be 30psi at idle, and rise to 37 while the pedal is depressed. What could be causing these issues? The outlet and return lines at the tank have been replaced, along with the ones attached to the fuel filter. Engines a fresh rebuild with new injectors as well, and a JWT programmed ecu. Im working on it tommorrow so a quick response to help get my baby back on the road would be GREATLY appreciated! Quote Link to comment Share on other sites More sharing options...
Domzs Posted November 9, 2011 Share Posted November 9, 2011 Hey all, I've recently replaced my stock N/A '87 fuel pump with a walbro 255lph, along with a new fuel filter and fuel pressure regulator. Before these changes the car had 30psi of fuel pressure measured after the fuel filter, but would drop to below that when the pedal was depressed. After these changes, the same thing occurs. The FSM states that it should be 30psi at idle, and rise to 37 while the pedal is depressed. What could be causing these issues? The outlet and return lines at the tank have been replaced, along with the ones attached to the fuel filter. Engines a fresh rebuild with new injectors as well, and a JWT programmed ecu. Im working on it tommorrow so a quick response to help get my baby back on the road would be GREATLY appreciated! Check your vac. lines to fuel press. regulator . Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 10, 2011 Share Posted November 10, 2011 Is the JWT EMS controlling the fuel pump voltage, like the ZX ECU does? ? Even with the vacuum line disconnected, you shouldn't get a pressure drop, unless the pump is getting a lower voltage. Maybe your EMS is dropping voltage or it's not raising voltage when it should. Quote Link to comment Share on other sites More sharing options...
BlueZ31 Posted November 10, 2011 Author Share Posted November 10, 2011 New question: The FSM states that "the moment the pedal is depressed" it should jump to 37 psi, which it does but then drops down to 30 or so. Does this mean its only supposed to spike to 37 and not actually stay there the entire time? Also, all these tests were done without load, I haven't done a driving fuel pressure test. Disconnecting the vac line to the regulator causes the pressure to jump to about 40psi or so, so I know the regulator is fine. I replace the fuel pressure regulator control solenoid and it seems to have made a difference. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 11, 2011 Share Posted November 11, 2011 Post #1 - Before these changes the car had 30psi of fuel pressure measured after the fuel filter, but would drop to below that when the pedal was depressed. After these changes, the same thing occurs. Last post - "the moment the pedal is depressed" it should jump to 37 psi, which it does but then drops down to 30 or so. You're saying two different things, from your first post to your last. Based on your last post, things are working correctly. The Engine Fuel section in the 280Z FSMs does a good job of describing the FPR's purpose. Better than the later ZX FSMs which just describe tests, but don't describe the purpose. The early FSM is worth downloading and reading the Engine Fuel section. Quote Link to comment Share on other sites More sharing options...
BlueZ31 Posted November 11, 2011 Author Share Posted November 11, 2011 "I replaced the fuel pressure regulator control solenoid and it seems to have made a difference." Things are different from my first post, based on replacing the FPRCS. Long story short, I just need to know if it should maintain 37psi while accelerating, or if it should only spike to that when the pedal is first depressed. Quote Link to comment Share on other sites More sharing options...
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