Guest Anonymous Posted January 23, 2003 Share Posted January 23, 2003 Given: '79ZX AT w/ stock EFI. Hesitation on accel. Already swapped out AFM (helped) and fixed a vac. leak (helped more). Still slight hesitation (haven't checked for fuel pressure rise on accel., but static seemed OK), and, FYI, fuel system does not retain pressure when engine is turned off. Simple Question: Is the Pressure Regulator supposed to close all the way when the engine is turned off? IE, is it one end of the pressure that is supposed to stay in the fuel system? Mercy requested.........I'm a carb guy trying to learn how to function in an FI world Thanks in advance.......... Quote Link to comment Share on other sites More sharing options...
Guest jt240z Posted January 23, 2003 Share Posted January 23, 2003 Yes, there should be some residual pressure left on the injector side of the pressure regulator. If you don't have pressure on the feed line, after the car has run and stopped for an hour, then you're leaking down some where. Here are some areas to look at: 1: You could have a faulty fuel pressure regulator leaking fuel past it. 2: There is a check valve in the fuel pump that is known to go bad. I've had two that did this. You need to replace the fuel pump to fix this. 3: You could have a leaky injector or cold start valve. A leaky injector or cold start valve would also tend to make the engine run rich. This would be most notable at idle. On earlier 280Zs, if your pressure is leaking down, then the car would be harder to start after sitting for a while. This may not be so true for a ZX, since the ECU runs for 5 seconds after the key ignition is turned on. That helps prime the system. I hope this helps. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 24, 2003 Share Posted January 24, 2003 Thanks, JT. Exactly what I wanted to know, and a bit more good stuff to check out. Question, though: If the one-way valve in the fuel pump is a known weak spot, why not put a third party one way valve in-line, either before or after the pump, and be done with it? A whole lot cheaper than replacing pumps @ $180 ea. I suspect I will be trying the in-line valve. Thanks, again. Quote Link to comment Share on other sites More sharing options...
Guest jt240z Posted January 24, 2003 Share Posted January 24, 2003 You can do that. The check valve must be located on the outlet (pressure) side of the pump. If it's put on the inlet side, the pump will have to pull gas through the valve and this may shorten the pump life. Quote Link to comment Share on other sites More sharing options...
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