I have a 99 cherokee sport was having issues with my fuel pump and put in a new Bosch fuel pump. All driving issues were solved BUT now if my car sits for awhile it cranks a long time. i assume it is losing pressure in the line somewhere if i were to begin to trouble shoot this where would i start the only other thread on here says check the gasket which i will do after i run this tank down. in the mean time what else can/should i check
thanks

 

I would definitely bust out a fuel pressure gauge. Buy a cheapie from harbor freight if you have too. I forget the exact increments for measuring pressure drop over time but if it's bleeding down too fast, you'll know right away.

 

Years ago I had this problem before replacing a fuel pump assembly. I remember the leak-down test spec as being the fuel system should hold at least 30 PSI for at least 5 mins. immediately after the engine is shut off.

Besides a fuel pressure tester you also need a T-adapter to determine if the leak is in the fuel rail / injectors or the fuel line or fuel pump assembly. The T-adapter needs to have quick connect fittings in order to connect to the fuel rail and fuel line.

T-adapters are included in some fuel pressure test kits. They also have individual T-adapter's for sale with the correct size quick connect fittings for the Jeep's fuel line. Quick connect fittings come in different sizes for different fuel systems, the Jeep uses a common size used by Chrysler and perhaps other auto manufactures.

You can make your own t-adapter if you have the correct size quick connect fittings, a piece of fuel line, t-block and schrader valve.
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Test for a fuel system leak by installing a fuel pressure guage on the fuel rail's port. First allow the engine to warm up and then shut the engine off. If fuel pressure drops below 30 psi in under 5 mins you have a fuel leak.

The next tests are to determine if the leak is in the fuel rail / injectors or the fuel line or fuel pump assembly.

Install the T-adapter between the fuel rail and fuel line.

To test for a leaks in the fuel rail / injectors. Place a clamp between the fuel rail and the T-adapter. After warming up the engine then shutting it off. If fuel pressure holds at 30 psi or above then the problem is with the fuel rail/injectors.

To test for leaks in the fuel pump assembly. Place a clamp between the t-adapter and fuel line. (warm up the engine then shut off) If fuel pressure holds at 30 psi or above then the leak is in the fuel line or fuel pump assembly.

The fuel pump assembly consists of two anti-drainback valves. One in the fuel pump and one in the regulator/filter.

A quick loss of pressure usually indicates a defective check valve in the filter/regulator. A slow loss of pressure usually indicates a defective check valve in the electric fuel pump.

1 – VEHICLE FUEL LINE
2 – TEST PORT “T”
4 – FUEL PRESSURE TEST GAUGE
5 – FUEL LINE CONNECTION AT RAIL
6 – FUEL RAIL