Strange Starting Problem
08-09-2009 | 06:17 AM
#1
Thread Starter
Junior Member
Joined: Jul 2009
Posts: 92
Likes: 0
Year: 1998
Model: Cherokee
Engine: 4.0
Strange Starting Problem
This one is beyond me! She won't start on first turn of key...even if you keep holding it for many seconds. However, she'll start right off on the second turn. Runs like a champ after that. Also, it only happens when cold. If you turn off and try again in 10 minutes...no problems. She's had a full tune up including press reg/filter. Is this a relay problem? I woudn't think it's the FP since everything runs fine after the second turn.
08-09-2009 | 08:28 AM
#5
Thread Starter
Junior Member
Joined: Jul 2009
Posts: 92
Likes: 0
Year: 1998
Model: Cherokee
Engine: 4.0
No check engine light, but will check for codes, my friend has my reader and need to get it back from him before I can check for codes.
Another thing to notice is the fact that I replaced the press reg/filter and this started happening shortly after it was replaced.
08-09-2009 | 08:36 AM
#6
Caracticus Potts The Mod
Joined: Jul 2009
Posts: 5,298
Likes: 9
From: Hainsville, NJ
Model: Grand Cherokee
Logical conclusion Captian. Does sound like the check valve on the fuel pump is bad. After a long sit time(overnight) all the fuel in the line could be draining back to the tank. You could put a FP guage on it and see how long it takes to drain back after sutting it off.
08-10-2009 | 06:37 AM
#7
Thread Starter
Junior Member
Joined: Jul 2009
Posts: 92
Likes: 0
Year: 1998
Model: Cherokee
Engine: 4.0
Logical conclusion Captian. Does sound like the check valve on the fuel pump is bad. After a long sit time(overnight) all the fuel in the line could be draining back to the tank. You could put a FP guage on it and see how long it takes to drain back after sutting it off.
, I want to make sure I get everything that needs replacing...
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08-12-2009 | 02:55 PM
#8
Junior Member
Joined: Mar 2009
Posts: 68
Likes: 0
From: Clarksville, TN
Year: 2000
Model: Cherokee
Engine: 4.0L I6
My 2K XJ is doing this EXACT SAME THING. It's really annoying and if replacing the fuel pump mean dropping the tank then it is definitely beyond my capabilities at this time. Not cool.
08-12-2009 | 03:39 PM
#9
Thread Starter
Junior Member
Joined: Jul 2009
Posts: 92
Likes: 0
Year: 1998
Model: Cherokee
Engine: 4.0
It's really not that hard. More awkward than anything since its a dirty and uncomfortable job. If you do it on a near empty tank...even easier. Everything is easily accessible from the bottom without having to lift the Jeep. I'm going to replace my fuel pump as soon as I find a good pump for 100 bones...I refuse to pay 300 for the OEM one. The hardest part is really having to crank the band bolts down since it's a super long threat.
08-13-2009 | 07:57 AM
#10
Newbie
Joined: Aug 2009
Posts: 9
Likes: 0
Model: Cherokee
I'm having the same problem. 2001 4.0, I've had a P0031, Cylinder 1 misfire detected, code over 6 times.
Replaced the Coil Rail. Plugs, twice. Camshaft position sensor. #1 injector.
Turning the key on and waiting a few seconds does seem to help when first starting a cold engine. But most of the time it takes two attempts to get the engine started.
I'm just about to the point of taking it to the dealer and taking it in the hip.
Help, please.
Replaced the Coil Rail. Plugs, twice. Camshaft position sensor. #1 injector.
Turning the key on and waiting a few seconds does seem to help when first starting a cold engine. But most of the time it takes two attempts to get the engine started.
I'm just about to the point of taking it to the dealer and taking it in the hip.
Help, please.
Last edited by red rider; 08-13-2009 at 08:24 AM.
08-13-2009 | 08:04 AM
#11
CF Veteran
Joined: Apr 2008
Posts: 13,952
Likes: 17
Model: Cherokee
For 96+ XJ's, From the FSM:
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
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
08-13-2009 | 08:58 AM
#12
Newbie
Joined: Aug 2009
Posts: 9
Likes: 0
Model: Cherokee
Okay. After reading the previous post I did some testing.
Connected gauge to fuel rail test port. Turned key on and observed pressure rise to 25 PSI and then fall to 10 PSI in 30 seconds.
Start engine, pressure raises to 45 PSI. Have a miss that goes away after revving the engine a few times.
Turned engine off, pressure falls to 10> PSI after 30 seconds. 0 PSI after 2 minutes.
Is this a fuel pressure/check valve problem? Does that explain the miss and P0301 codes?
I'm familiar with Ford FI systems that have a supply line, pressure valve and return line to tank. This system (jeep) has only one line with a (pressure relief?) valve mid point in the fuel rail? If I understand correctly, the valve that maintains correct pressure on the fuel rail/injectors is in the fuel pump/tank?
Thanks
Connected gauge to fuel rail test port. Turned key on and observed pressure rise to 25 PSI and then fall to 10 PSI in 30 seconds.
Start engine, pressure raises to 45 PSI. Have a miss that goes away after revving the engine a few times.
Turned engine off, pressure falls to 10> PSI after 30 seconds. 0 PSI after 2 minutes.
Is this a fuel pressure/check valve problem? Does that explain the miss and P0301 codes?
I'm familiar with Ford FI systems that have a supply line, pressure valve and return line to tank. This system (jeep) has only one line with a (pressure relief?) valve mid point in the fuel rail? If I understand correctly, the valve that maintains correct pressure on the fuel rail/injectors is in the fuel pump/tank?
Thanks
08-13-2009 | 10:08 AM
#13
CF Veteran
Joined: Apr 2008
Posts: 13,952
Likes: 17
Model: Cherokee
What you are calling a relief valve is not a releif valve at all, it's a damper to prevent pulsation in the rail.
The 96+ system is a returnless system. any pressure above 49 +/- 5 psi is returnrd to the tank via the pressure regulator in the Fuel Pump Assy.
The failure to maintain pressure could be the check valve, but I'd also look at the injectors too. You may very well have one that is stuck open. The PCM will report an error if it does not sense the injector(s) opening.
The 96+ system is a returnless system. any pressure above 49 +/- 5 psi is returnrd to the tank via the pressure regulator in the Fuel Pump Assy.
The failure to maintain pressure could be the check valve, but I'd also look at the injectors too. You may very well have one that is stuck open. The PCM will report an error if it does not sense the injector(s) opening.
08-13-2009 | 04:17 PM
#14
Newbie
Joined: Aug 2009
Posts: 9
Likes: 0
Model: Cherokee
If an injector were stuck open, wouldn't that cause a constant miss?
The only time I'm getting a noticeable miss is on start-up. That goes away after a few seconds or after revving the engine a few time.
The dealer tech said to check compression for a bad head gasket. Not using oil, not smoking, temp not rising, no oil in coolant or coolant in oil.
This thing is really got me stumped.
Could it be computer related?
Hey, al2ride, is any of this helping you?
The only time I'm getting a noticeable miss is on start-up. That goes away after a few seconds or after revving the engine a few time.
The dealer tech said to check compression for a bad head gasket. Not using oil, not smoking, temp not rising, no oil in coolant or coolant in oil.
This thing is really got me stumped.
Could it be computer related?
Hey, al2ride, is any of this helping you?
