1991 Dodge Dynasty car start only after pressuring fuel sys

BILLGREGO

MEMBER
1991 DODGE DYNASTY
6 CYL
FWD
AUTOMATIC
125,675 MILES

1991 Dodge Dynasty LE 3.3 engine. Fuel pressure reads 43 at the rail while engine is running, but drops instantly to zero when ignition is turned off. When this happens, the engine will not start until I put 12 volts directly to the fuel pump. The pressure jumps to 40 and the car will start. As long as the engine is running a fuel pressure of 41 is maintained and the engine runs with great power. I have heard there is a fuel pressure release valve in the fuel rail circuit to drop fuel pressure to zero (after engine shut down) for changing injectors or any other fuel related parts. Could this valve somehow be opening at ignition shutdown when it should not?
An answer will be sincerely appreciated.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

I is a manually operated valve, so I would say no. If you are droping to 0 psi as soon as you shut the engine, there is an antiflow back valve in the fuel pump and should be one in the fuel filter that may cause it. Other than that, you have a leak or a leaking injector.

When you try to restart it, can you hear the pump actuate? If you cycle the key on and off several times then try, will it start? Have you replaced the fuel pump relay?