Fuel pressure dropping
 

I have had this problem with my old engine and now with my new one. The car doesnt seem to want to hold pressure when i turn the car off. The fuel system is as follows, Kgparts secondary rail, and milled primary rail. 850 and 1680 injectors. SX Fuel pressure regulator. Supra TT pump. New insulators on the primary and the aluminum spacer for the secondary. I also bough new diffusers for the primary as well.

My car will pressurize to 42 psi when the key is turned but it will not hold that pressure at all when the car is off. I have checked for leaks and cannot find any. I took the pump back out and replaced the O ring and made sure everything was a lot more snug. Still wont hold.

There are two check valves ontop of the fuel pump, if these were bad would it cause a loss of pressure when the Fuel pump is not on?

Would having the FPR going to the return line cause this loss of pressure? Since it would be coming into the fuel system and passing the FPR and than going back out into the return line causing it not to hold the pressure?

Any opinions are welcome so i can track this down?

Thanks Jake

It is common for the check valve in the pump to leak and not hold fuel pressure. Not holding fuel pressure in and of itself it not a problem. Are you trying to track a fuel issue, like a leaky injector? If so, pressure up your fuel system and immediatley pinch off the pressure and return lines. Then see if you still are bleeding pressure.

Thanks, I forgot to put that i just had my injectors cleaned and flow tested. I just wanted to make sure i was able to hold pressure, and if not if there was a problem.

I just had 30 injectors cleaned and flow tested, at this current moment 9 have failed on me by either getting stuck open or leaking externally out of the top(all stock injectors) I still have about 5-6 more injectors I havent tried but at this point I am almost afraid too. If it is the injectors leaking you will notice the car will be difficult to start and a lot of black smoke will be evident when you start the car, if not, it probably isnt injector related.

the FPR is supposed to be on the return line. otherwise there would be a pressure drop for the other injectors in the line. If your Gauge is on the FPR the pressure will drop off fairly quickly. That doesnt mean the rails arent still pressurized though. If you are trying to do the pressure test you would have to put the gauge inline before the FPR. This is the case at least with aeromotive FPR's which is what i'm running. I imagine it effects others as well. This is normal. I wouldnt worry about it unless you have issues with the car running excessively rich especially on start up.

Thanks that is what i was looking for. Hopefully this helps out others that might have the same problem.

I had the same problem and replaced the pump and injectors. The pressure still drops off quickly on the FPR gauge and the car doesn't like starting right away when cold.