OT 1997 Jeep Grand Cherokee


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Posted by Paul(in NY) [209.23.100.167] on Saturday, September 12, 2015 at 15:24:48 :

I have a 1997 Jeep Cherokee to keep miles off my Ram CTD. It has always started instantly, even in sub zero weather. Two days ago, she started to have a long crank time, after sitting for a while. She always started instantly on the second crank attempt. When you turn the key to on, the computer starts the in tank fuel pump for 3 seconds to bring the fuel rail up to pressure.

This morning I did a check on the fuel system. Factory Specs are 49 psi at the fuel rail +- 5 psi and the flow rate is 1 pint in 15 seconds.

Test; Engine had not run since yesterday afternoon. Key on, pump ran about 3 seconds, fuel pressure at the rail was 5 psi. Key off/on fuel pressure at the rail 49 psi. Engine running, fuel bleed valve on the fuel pressure gauge wide open dumping into a bottle, I still had 30 psi at the rail, and easily 1 pint of fuel in the bottle in 15 seconds. The fuel pump is fine !

Bleed down factory specs are; must maintain 24 psi for at least 5 minutes. With 49 psi on the rail, shut down, 30 seconds down to 30 psi, 1 min down to 20 psi, 2 min down to 10 psi, 2 min 30 seconds fuel pressure to zero. This indicates either leaking injectors (confident mine are good) or the fuel pressure regulator check valve is leaking. Once at zero pressure the fuel drains back to the tank.

Before I drop the skid plate, fuel tank to get to the pump regulator, I am wondering; The fuel system is built for the 50 psi fuel pressure. Why not disconnect the fuel line at the rail and give some low pressure ( few pounds) air pressure into the fuel line to see if it might blow any junk out of the check valve at the pump/tank ??? The alternative is a lot of work and $150 for a new OEM Bosch pump module.

Anyone have any other ideas to possibly clear the check valve ??

Thanks
Paul




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