l28t260z Posted July 12, 2007 Share Posted July 12, 2007 im new to this site i have a problem with my fuel pressure. it stays at 60 psi and then it start buzzing then drops at 50psi. if anybody has a answer to my problem i would be appreciated. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 12, 2007 Administrators Share Posted July 12, 2007 First off, welcome to Hybridz, your one stop source for all things extreme Z car related... Now to your issue... 1) Is your car stock, modified, etc? 2) What year is it? 3) What is your mechanical aptitude, i.e. are comfortable with getting your hands dirty working on your car and somewhat EFI savvy? 4) Where are getting your fuel pressure reading from? Based on the limited description you gave, it sounds like your fuel isn’t returning back to your tank, (i.e. no fuel FLOW due to a clogged return line or incorrectly plumbed fuel system), and as result you are severely over working your fuel pump. Don’t let your fuel pump run in this situation. It will burn up VERY quickly if it hasn’t already and they are not cheap. If you don’t already have one, go down to the parts store and purchase a Haynes manual for your car. It has the fuel routing diagram. Make sure your car matches that diagram EXACTLY. I’ve attached a very simplified version of the fuel routing. This is how yours should be routed with the addition of the fuel filter, fuel damper at the pump, etc. Quote Link to comment Share on other sites More sharing options...
l28t260z Posted July 12, 2007 Author Share Posted July 12, 2007 i have a 1974 260z with a 280zx turbo engine. costom intake manifold,fuel rail,performance fuel pressure regulator,upgrade turbo, external waste gate,and runing two fuel pumps. im getting my fuel pressure reading from a gauge connected to fuel pressure regulator. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 12, 2007 Administrators Share Posted July 12, 2007 Your fuel pressure regulator is most likely adjustable. But first verify that your return line is indeed returning fuel back to the tank. Then, be sure that those two pumps aren’t pumping MORE fuel than the return line can flow, i.e. did you size your fuel line for the both pumps capacity? Did you verify fuel line routing as mentioned above? Still LOTS of unknowns here. You can't just throw out a "fuel pressure" and say "fuel pump buzzes" and expect us to just “guess” for 20 posts. We need a lot more detail of possibly how and why that could be or if it is even a malfunction? Maybe your fuel pressure regulator is set at 60 PSI, and your pumps are making normal noises because they are race pumps that are supposed to be noisy? Are the pumps stock, aftermarket? .. Did the car run with this setup before? If so, what changed? Please, throw us a bone and we’ll help as much as we can. Quote Link to comment Share on other sites More sharing options...
l28t260z Posted July 12, 2007 Author Share Posted July 12, 2007 yes fuel is going back to the tank. how can i check how much fuel pressure is going back to the tank? i do have the fuel line routing the way it shows. the pumps are aftermarket. the car has been runing this setup for three months now.yesterday i drove the car and would boost but it wouldnt go. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 13, 2007 Administrators Share Posted July 13, 2007 Are you using the stock ECU or aftermarket? So it will run, boost will build, the engine just doesn't seem to be making anymore power while on boost. Am understanding that correctly? Quote Link to comment Share on other sites More sharing options...
l28t260z Posted July 13, 2007 Author Share Posted July 13, 2007 yes im using the stock ECU. Quote Link to comment Share on other sites More sharing options...
rags Posted July 13, 2007 Share Posted July 13, 2007 I'd start by verifying fuel pressure while the car is building boost. Your going to have to have a remote fuel pressure guage. I use one attached to a schrader valve I have on a custom fuel rail. The guage has a lengh of high pressure hose between the guage and fitting for the schradr valve. I duct tape the gauge to the windshield and take the car fr a ride, build boost and see where the pressure goes. Also, you didn't confirm if the fuel pressure regulator is adjustable. If it is, can you adjust the pressure up and down while the car is idling? You said you have seen 60lbs., can you dial back to 40 with the vacuum sensing hose disconnected from the AFR and plugged? Joe Quote Link to comment Share on other sites More sharing options...
l28t260z Posted July 13, 2007 Author Share Posted July 13, 2007 i verifyed the fuel pressure while boosting at 9 pounds of boost the fuel pressure rises to 120 psi. yes the regulator is adjustable and i can also adjust it when idling. i think i can only dial back from the regulator. Quote Link to comment Share on other sites More sharing options...
rags Posted July 13, 2007 Share Posted July 13, 2007 120psi? And you don't have 30 year old hoses leaking everywhere? Adjust the fuel pressure regulator down to 40 lbs with the vacuum hose off and plugged. Reconnect the vacuum hose and let us know what the reading is. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 13, 2007 Administrators Share Posted July 13, 2007 Joe, Thanks for jumping in and helping out with this one. Btw, Ron says he enjoyed chatting with you, brought back memories. Some day we’ll all have to get together and swap V-8Z stories. Sorry for the tangent. Quote Link to comment Share on other sites More sharing options...
l28t260z Posted July 13, 2007 Author Share Posted July 13, 2007 i change the fuel hoses when i did the turbo upgrade. i adjusted the fuel pressure down to 40 lbs and i took it out for a ride and it wouldnt boost or go it just boggs out. i think the reason why is becuase the costom intake manifold and 90mm throttle body. Quote Link to comment Share on other sites More sharing options...
l28t260z Posted July 14, 2007 Author Share Posted July 14, 2007 thanks for the help pual and joe. i found out the problem. the wiring for my fuel pump was burning up and it would cause my fuel pump to turn off and on. have to fix 30 year old wires Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 15, 2007 Administrators Share Posted July 15, 2007 That is good news. Well, good that you found the problem any how and that it should be an easy inexpensive fix. Thank you for giving us the update. Take care, Paul Quote Link to comment Share on other sites More sharing options...
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