Hey all,

Has anyone ever heard of this? Truck quit running. Couldn't smell gas so I suspected fuel delivery. Mounted fuel pressure gauge on the fitting on the fuel rail behind the intake, reading was 27 psi. Not good, so I changed out fuel pump (rather than lowering tank or lifting box, I removed bed liner and cut an access hole in the bed, right over pump assembly nest). Before hooking up hoses, I installed my fuel pressure gauge on the output line fitting of the pump assembly. Turned the ignition key to on, and I could hear the pump run its 2 sec. cycle. I repeated this, cycling the pump, but could only get the pump to build up 26 psi, right at the assembly. Suspected a bad new pump so I returned it and exchanged it for another (Bosch #69225), and had the same results. By now I was doubting my pressure gauge, so I went back to the parts store and bought another one of those too. It read he same as my other gauge. Thought that I would go ahead and connect the supply line and take a pressure reading up on the rail. Left the return line off just in case the fule pressure regulator may also be leaking back to the tank. No fuel returned, and the best pressure that I could achieve at the rail was 21 psi. The fuel pump relay cycles every time I turn the key on for its 2 seconds. And it comes on when I crank the engine. Is it possible that I could have gotten two bad new Bosch pumps in a row? Or is the relay output voltage possibly an issue here?

 

Reading the pressure at the rail, dosen't tell you what the pump is putting out. There is a pressure regulator that controls the fuel pressure from the pump to the system, check that.

 

I also read the pressure at the pump discharge fitting while I had the lines disconnected, bypassing the fuel supply system going up to the engine. In that case fuel would never make it up to the pressure regulator. I also changed the supply hose going from the pump to the assembly discharge fitting, in case the old one was leaking. Also the readings I got did not bleed back either, they were just very low.