'98XJ4life

This is for anyone having slow starts but plenty of crank on a '97 and newer Jeep XJ's.(i.e. poor fuel pressure during crank) Starting two years ago I randomly started having a starting problem with my 98 Xj with 100k miles. it slowly got worse and so I replaced my fuel pressure regulator/filter and a new BOSCH pump. Like a $400.00 job just in parts. After all that I still had the same problem but now its worse so I thought it was something else. Turns out i still have bad fuel pressure and the BWD fuel regulator/filter (specific to '97 and newer XJs) or the BOSCH pump has a faulty check valve. Since both parts have a seperate check valve I am pulling my tank down and doing the whole thing again with a new set of parts thanx to Advance. Word of advice. read this. And then just simply install an external check valve. FUEL PRESSURE LEAK DOWN TEST
Use this test in conjunction with the Fuel Pump
Pressure Test and Fuel Pump Capacity Test.
Check Valve Operation: The electric fuel pump
outlet contains a one-way check valve to prevent fuel
flow back into the tank and to maintain fuel supply
line pressure (engine warm) when pump is not operational.
It is also used to keep the fuel supply line
full of gasoline when pump is not operational. After
the vehicle has cooled down, fuel pressure may drop
to 0 psi (cold fluid contracts), but liquid gasoline will
remain in fuel supply line between the check valve
and fuel injectors. Fuel pressure that has
dropped to 0 psi on a cooled down vehicle
(engine off) is a normal condition. When the electric
fuel pump is activated, fuel pressure should
immediately (1–2 seconds) rise to specification.
Abnormally long periods of cranking to restart a
hot engine that has been shut down for a short
period of time may be caused by:
† Fuel pressure bleeding past a fuel injector(s).
† Fuel pressure bleeding past the check valve in
the fuel pump module.
(1) Disconnect the fuel inlet line at fuel rail. Refer
to Fuel Tubes/Lines/Hoses and Clamps in this section
of the group for procedures. On some engines, air
cleaner housing removal may be necessary before
fuel line disconnection.
(2) Obtain correct Fuel Line Pressure Test Adapter
Tool Hose. Tool number 6539 is used for 5/16” fuel
lines and tool number 6631 is used for 3/8” fuel lines.
(3) Connect correct Fuel Line Pressure Test
Adapter Tool Hose between disconnected fuel line
and fuel rail (Fig. 8).
Fig. 7 Fuel Pressure Test Gauge (Typical Gauge
Installation at Test Port)
XJ FUEL SYSTEM 14 - 7
DIAGNOSIS AND TESTING (Continued)
(4) Connect the 0-414 kPa (0-60 psi) fuel pressure
test gauge (from Gauge Set 5069) to the test port on
the appropriate Adaptor Tool. The fittings on both
tools must be in good condition and free from
any small leaks before performing the proceeding
test.
(5) Start engine and bring to normal operating
temperature.
(6) Observe test gauge. Normal operating pressure
should be 339 kPa 6 34 kPa (49.2 psi 6 5 psi).
(7) Shut engine off.
(8) Pressure should not fall below 30 psi for five
minutes.
(9) If pressure falls below 30 psi, it must be determined
if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking.
(10) Again, start engine and bring to normal operating
temperature.
(11) Shut engine off.
(12) Testing for fuel injector or fuel rail leakage:
Clamp off the rubber hose portion of Adaptor
Tool between the fuel rail and the test port “T” on
Adapter Tool. If pressure now holds at or above 30
psi, a fuel injector or the fuel rail is leaking.
(13) Testing for fuel pump check valve, filter/
regulator check valve or fuel tube/line leakage:
Clamp off the rubber hose portion of Adaptor Tool
between the vehicle fuel line and test port “T” on
Adapter Tool. If pressure now holds at or above 30
psi, a leak may be found at a fuel tube/line. If no
leaks are found at fuel tubes or lines, one of the
check valves in either the electric fuel pump or filter/
regulator may be leaking.
Note: 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.
The electric fuel pump is not serviced separately.
Replace the fuel pump module assembly. The filter/
regulator may be replaced separately on certain
applications. Refer to Fuel Filter/Fuel Pressure Regulator
Removal/Installation for additional information

kurtdaniel

A bad check valve fuel pump would give symptoms like this. ... double check the primer bulb, cheap ones can bugger up even brand new. in a