2001 Jeep Cherokee 4.0 long cranking, slow start?

Question

changed fuel pump, crank position sensor, plugs and fuel cap..still have same problem. Any suggestions will be welcome. Thanks

Answer 1

Perhaps you have a leaky injector (1st guess), or Check-Valve on the new pump is not sealing properly, or the Fuel Pressure Regulator is not working properly.

Here's a test:

DIAGNOSIS AND TESTING
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:
² Fuel pressure bleeding past a fuel injector(s).
² Fuel pressure bleeding past the check valve in
the fuel pump module.
² A defective fuel filter/pressure regulator.
Two #6539, 5/16”, Fuel Line Pressure Test Adapter
Hose Tools are required for the following tests.
(1) Release fuel system pressure. Refer to Fuel
Pressure Release Procedure.
(2) Raise vehicle.
Fuel Line Identification: The fuel filter/pressure
regulator is located in front of the fuel tank and
above the rear axle. It is transversely mounted to a
chassis crossmember (left-to-right). The filter/regulator
is equipped with 3 fuel line fittings (2 at one end
and 1 at the other end). The single fitting facing the
left side of the vehicle is the supply line to the fuel
rail (Fig. 1) . The 2 fittings facing the right side of
the vehicle are connected to the fuel tank. Of these 2
fittings, the fitting towards the front is used for fuel
return to the fuel tank. The fitting towards the rear
is a pressure line. This rear fitting must be disconnected
for the following step.
(3) See previous step. Disconnect fuel pressure line
at rear of filter/regulator. This is a 5/169 quick-connect
fitting (Fig. 1) . Refer to Quick-Connect Fittings
for procedures.
(4) Obtain correct Fuel Line Pressure Test Adapter
Hose Tool # 6539 for 5/16” fuel lines. Connect one
end of this Special Tool into the disconnected fuel
pressure line. Connect the other end of the Tool into
fitting on filter/regulator.
(5) Lower vehicle.
(6) Disconnect the fuel inlet line at fuel rail. Refer
to Quick-Connect Fittings for procedures. On some
engines, air cleaner housing removal may be necessary
before fuel line disconnection.
(7) Obtain a second Fuel Line Pressure Test
Adapter Hose Tool # 6539 for 5/16” fuel lines. Connect
this tool between disconnected fuel line and fuel
rail (Fig. 2) .
(8) 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. NOTE: The DRB III
Scan Tool along with the PEP module, the 500
psi pressure transducer, and the transducer-totest
port adapter may also be used in place of
the fuel pressure gauge.
CAUTION: The fittings on both tools must be in
good condition and free from any small leaks
before performing the proceeding test.
(9) Start engine and bring to normal operating
temperature.
(10) Observe fuel pressure test gauge (or DRB
screen). Normal operating pressure should be 339
kPa ± 34 kPa (49.2 psi ± 5 psi).
(11) Shut engine off.
(12) Pressure should not fall below 30 psi for five
minutes.
(13) If pressure falls below 30 psi, it must be
determined if a fuel injector, the supply check valve
within the fuel pump module, the fuel filter/pressure
regulator, or a fuel tube/line is leaking.
(14) Again, start engine and bring to normal operating
temperature.
(15) Shut engine off.
(16) Testing for fuel injector or fuel rail leakage:
Clamp off the rubber hose portion of the 6539
Adaptor Tool between the fuel rail and the test port
“T” on Adapter Tool (be sure clamping pressure is
sufficient). If pressure now holds at or above 30 psi, a
fuel injector or the fuel rail is leaking.
(17) Again, start engine and bring to normal operating
temperature.
(18) Shut engine off.
(19) Raise vehicle.
(20) Testing for fuel filter/pressure regulator
leakage: While continuing to securely clamp
between the fuel rail and the test port 9T9 on Adaptor
Tool 6539, securely clamp off any rubber hose portion
of the Adaptor Tool 6539 that was installed
between the fuel pressure line and the filter/regulator
fitting (by restricting the pump module supply
line’s backflow, you isolate any leakdown originating
from the filter/regulator via the tank return line.) If
the pressure falls below 30 psi within 5 minutes, the
filter/regulator is leaking. If it now holds at or above
30 psi, the electric fuel pump check valve is leaking
or a fuel tube/line is leaking. A fuel odor presence
would indicate the latter.
The electric fuel pump is not serviced separately. If
replacement is necessary, replace the fuel pump module
assembly. The filter/regulator may be replaced
separately. Refer to Fuel Filter/Fuel Pressure Regulator
Removal/Installation for additional information.

Answer 2

First scan for codes, the 4.0 sometimes cranks a long time just due to its nature, when starting let the check engine light and rest of the self test lights clear off before starting, that way the pcm gets an accurate picture of the starting conditons, the last thing I would try is a fuel pressure regulator

Answer 3

Is it cold outside?? If so, your battery may be wearing down and you no longer have the same amount of Cold Cranking Amps (CCAs) you used to. I had this problem with my '95, replaced my battery with an red topped optima (little cheaper than the yellow but still has high CCAs). Get yourself an optima (red, yellow, or blue) and you'll be doing 2 things for yourself:

-Higher CCAs...just like it sounds, amount of amps put out at freezing temps

-Deep Cycle...basically sayin you can run more stuff streight off of it before the voltage drops too low...such as lights, winch, welder, on board air, radio, etc.

http://www.quadratec.com/products/17003_02.htm

Answer 4

install a new improve fuel injector insulator. this will reduce fuel vapor at the injectors which cause long cranking. part number 56028371AA

Answer 5

when it is cold my j eep dosnt like to crank. is cold natured and i had to buy a new battery.