I have a 1979 280zx. The engine is running pretty rough and has a lack of power. I noticed an interesting pattern though after working on it. Every time I open up the fuel system to work on it and then close it back up (reconnect and tighten all hoses) it runs great for only 5 - 10 minutes! Could this be the fuel damper or fuel pressure regulator? I have replaced the fuel regulator and installed a pressure gaur and all appears okay. What could be going on here?? I would appreciate your help!

Thanks! steady88

 

What is the fuel pressure when idling?
Does it change when revving?
When was the last major tune up (plugs, wires, cap, rotor)?
Have you checked all sensors and connections to make sure they are tight & free of corrosion?

 

fuel filter could be suspect. it can have pressure but no volume.