96 Grand Cherokee Stalling
11-26-2006, 07:42 PM
#83
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
From the '96 FSM
DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST-4.0L ENGINE
NOTE: The fuel pressure test port is used on certain
engines only. If equipped, the test port will be
located on the fuel rail (Fig. 8). A sealing cap is
screwed onto the test port.
All fuel systems are equipped with a fuel tank module
mounted, fuel pressure regulator. The fuel pressure regulator
is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure
should be 338 kPa 6 14 kPa (49.0 psi 6 2 psi).
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN TESTING FUEL SYSTEM PRESSURE.
(1) Remove the protective cap at the fuel rail test
port. Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from gauge set 5069) to the test port pressure
fitting on the fuel rail.
(2) Start the engine and note pressure gauge reading.
Fuel pressure should be 338 kPa 6 14 kPa (49.0
psi +/- 2 psi) at idle.
(3) If pressure is at O psi, connect DRB scan tool
and refer to operating instructions in the appropriate
Powertrain Diagnostics Procedures service manual.
(4) If operating pressure is above 51.0 psi, fuel
pump is OK but pressure regulator is defective. Regulator
is not serviced separately. Replace fuel pump
module assembly.
FUEL PRESSURE LEAK DOWN TEST
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.
(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) Connect the appropriate Fuel Line Pressure
Test Adapter Tool (number 6539, 6631, 6541 or 6923)
between the disconnected fuel line and fuel rail (Fig.
11) or (Fig. 12).
(3) 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.
(4) Start engine and bring to normal operating
temperature.
(5) Observe test gauge. Normal operating pressure
should be 338 kPa 6 14 kPa (49 psi 6 2 psi).
(6) Shut engine off.
(7) Pressure should not fall below 24 psi for five
minutes.
(8) If pressure falls below 24 psi, it must determined
if a fuel injector, the fuel pressure regulator or
a fuel tube/line is leaking.
(9) Again, start engine and bring to normal operating
temperature.
(10) Shut engine off.
(11) Checking for fuel injector 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 24 psi, a fuel injector
or the fuel rail is leaking.
(12) Checking for fuel pump module 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 24 psi, a leak can be found at a fuel tube/
line. If no leaks are found at fuel tubes or lines,
replace the fuel pump module.
"DougW" <post.replies@invalid.address> wrote in message
news:hGpah.43$DF6.28@newsfe24.lga...
> dougguitar@yahoo.com wrote:
>> DougW wrote:
>>> It should hold pressure for over 4-5 hours. Given this and your
>>> 45psi for fuel pressure I'm starting to think the regulator might be
>>> shot. When you take the vac line off see if there is gas dribbling
>>> out.
>>>
>>> --
>>> DougW
>>
>> OK, I timed it. After 4 minutes, the pressure had dropped from around
>> 49 psi to about 35 psi. After 12 minutes, it had dropped to 20 psi. To
>> add to my fun, the 96 GC does not have the fuel pressure regulator
>> attached to the fuel rail: it's built into the fuel pump. @#$%
>> There's just a direct connect fuel line going to the fuel rail.
>>
>> Will a regulator fail in this intermittent way? If that's the case,
>> then I have to pony up the $300 plus for a new fuel pump. Sure wish I
>> could be sure before I make the financial plunge.
>
> Hard to tell, the 96 made a lot of changes and my books are only good
> up to the 95. 49 psi might be normal. Still though I thought pressure
> was supposed to be maintained longer than that. I'd suggest calling a
> dealership and asking if a mechanic could look that up for you. It's
> worth a shot.
>
> I don't think it is your fuel pump. Pumps and pressure regulators
> usually fail to the low pressure side and what you get is a lack of
> power at wide-open-trottle or even pinging.
>
> --
> DougW
>
>
>
DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST-4.0L ENGINE
NOTE: The fuel pressure test port is used on certain
engines only. If equipped, the test port will be
located on the fuel rail (Fig. 8). A sealing cap is
screwed onto the test port.
All fuel systems are equipped with a fuel tank module
mounted, fuel pressure regulator. The fuel pressure regulator
is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure
should be 338 kPa 6 14 kPa (49.0 psi 6 2 psi).
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN TESTING FUEL SYSTEM PRESSURE.
(1) Remove the protective cap at the fuel rail test
port. Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from gauge set 5069) to the test port pressure
fitting on the fuel rail.
(2) Start the engine and note pressure gauge reading.
Fuel pressure should be 338 kPa 6 14 kPa (49.0
psi +/- 2 psi) at idle.
(3) If pressure is at O psi, connect DRB scan tool
and refer to operating instructions in the appropriate
Powertrain Diagnostics Procedures service manual.
(4) If operating pressure is above 51.0 psi, fuel
pump is OK but pressure regulator is defective. Regulator
is not serviced separately. Replace fuel pump
module assembly.
FUEL PRESSURE LEAK DOWN TEST
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.
(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) Connect the appropriate Fuel Line Pressure
Test Adapter Tool (number 6539, 6631, 6541 or 6923)
between the disconnected fuel line and fuel rail (Fig.
11) or (Fig. 12).
(3) 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.
(4) Start engine and bring to normal operating
temperature.
(5) Observe test gauge. Normal operating pressure
should be 338 kPa 6 14 kPa (49 psi 6 2 psi).
(6) Shut engine off.
(7) Pressure should not fall below 24 psi for five
minutes.
(8) If pressure falls below 24 psi, it must determined
if a fuel injector, the fuel pressure regulator or
a fuel tube/line is leaking.
(9) Again, start engine and bring to normal operating
temperature.
(10) Shut engine off.
(11) Checking for fuel injector 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 24 psi, a fuel injector
or the fuel rail is leaking.
(12) Checking for fuel pump module 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 24 psi, a leak can be found at a fuel tube/
line. If no leaks are found at fuel tubes or lines,
replace the fuel pump module.
"DougW" <post.replies@invalid.address> wrote in message
news:hGpah.43$DF6.28@newsfe24.lga...
> dougguitar@yahoo.com wrote:
>> DougW wrote:
>>> It should hold pressure for over 4-5 hours. Given this and your
>>> 45psi for fuel pressure I'm starting to think the regulator might be
>>> shot. When you take the vac line off see if there is gas dribbling
>>> out.
>>>
>>> --
>>> DougW
>>
>> OK, I timed it. After 4 minutes, the pressure had dropped from around
>> 49 psi to about 35 psi. After 12 minutes, it had dropped to 20 psi. To
>> add to my fun, the 96 GC does not have the fuel pressure regulator
>> attached to the fuel rail: it's built into the fuel pump. @#$%
>> There's just a direct connect fuel line going to the fuel rail.
>>
>> Will a regulator fail in this intermittent way? If that's the case,
>> then I have to pony up the $300 plus for a new fuel pump. Sure wish I
>> could be sure before I make the financial plunge.
>
> Hard to tell, the 96 made a lot of changes and my books are only good
> up to the 95. 49 psi might be normal. Still though I thought pressure
> was supposed to be maintained longer than that. I'd suggest calling a
> dealership and asking if a mechanic could look that up for you. It's
> worth a shot.
>
> I don't think it is your fuel pump. Pumps and pressure regulators
> usually fail to the low pressure side and what you get is a lack of
> power at wide-open-trottle or even pinging.
>
> --
> DougW
>
>
>
11-26-2006, 07:42 PM
#84
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
From the '96 FSM
DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST-4.0L ENGINE
NOTE: The fuel pressure test port is used on certain
engines only. If equipped, the test port will be
located on the fuel rail (Fig. 8). A sealing cap is
screwed onto the test port.
All fuel systems are equipped with a fuel tank module
mounted, fuel pressure regulator. The fuel pressure regulator
is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure
should be 338 kPa 6 14 kPa (49.0 psi 6 2 psi).
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN TESTING FUEL SYSTEM PRESSURE.
(1) Remove the protective cap at the fuel rail test
port. Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from gauge set 5069) to the test port pressure
fitting on the fuel rail.
(2) Start the engine and note pressure gauge reading.
Fuel pressure should be 338 kPa 6 14 kPa (49.0
psi +/- 2 psi) at idle.
(3) If pressure is at O psi, connect DRB scan tool
and refer to operating instructions in the appropriate
Powertrain Diagnostics Procedures service manual.
(4) If operating pressure is above 51.0 psi, fuel
pump is OK but pressure regulator is defective. Regulator
is not serviced separately. Replace fuel pump
module assembly.
FUEL PRESSURE LEAK DOWN TEST
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.
(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) Connect the appropriate Fuel Line Pressure
Test Adapter Tool (number 6539, 6631, 6541 or 6923)
between the disconnected fuel line and fuel rail (Fig.
11) or (Fig. 12).
(3) 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.
(4) Start engine and bring to normal operating
temperature.
(5) Observe test gauge. Normal operating pressure
should be 338 kPa 6 14 kPa (49 psi 6 2 psi).
(6) Shut engine off.
(7) Pressure should not fall below 24 psi for five
minutes.
(8) If pressure falls below 24 psi, it must determined
if a fuel injector, the fuel pressure regulator or
a fuel tube/line is leaking.
(9) Again, start engine and bring to normal operating
temperature.
(10) Shut engine off.
(11) Checking for fuel injector 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 24 psi, a fuel injector
or the fuel rail is leaking.
(12) Checking for fuel pump module 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 24 psi, a leak can be found at a fuel tube/
line. If no leaks are found at fuel tubes or lines,
replace the fuel pump module.
"DougW" <post.replies@invalid.address> wrote in message
news:hGpah.43$DF6.28@newsfe24.lga...
> dougguitar@yahoo.com wrote:
>> DougW wrote:
>>> It should hold pressure for over 4-5 hours. Given this and your
>>> 45psi for fuel pressure I'm starting to think the regulator might be
>>> shot. When you take the vac line off see if there is gas dribbling
>>> out.
>>>
>>> --
>>> DougW
>>
>> OK, I timed it. After 4 minutes, the pressure had dropped from around
>> 49 psi to about 35 psi. After 12 minutes, it had dropped to 20 psi. To
>> add to my fun, the 96 GC does not have the fuel pressure regulator
>> attached to the fuel rail: it's built into the fuel pump. @#$%
>> There's just a direct connect fuel line going to the fuel rail.
>>
>> Will a regulator fail in this intermittent way? If that's the case,
>> then I have to pony up the $300 plus for a new fuel pump. Sure wish I
>> could be sure before I make the financial plunge.
>
> Hard to tell, the 96 made a lot of changes and my books are only good
> up to the 95. 49 psi might be normal. Still though I thought pressure
> was supposed to be maintained longer than that. I'd suggest calling a
> dealership and asking if a mechanic could look that up for you. It's
> worth a shot.
>
> I don't think it is your fuel pump. Pumps and pressure regulators
> usually fail to the low pressure side and what you get is a lack of
> power at wide-open-trottle or even pinging.
>
> --
> DougW
>
>
>
DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST-4.0L ENGINE
NOTE: The fuel pressure test port is used on certain
engines only. If equipped, the test port will be
located on the fuel rail (Fig. 8). A sealing cap is
screwed onto the test port.
All fuel systems are equipped with a fuel tank module
mounted, fuel pressure regulator. The fuel pressure regulator
is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure
should be 338 kPa 6 14 kPa (49.0 psi 6 2 psi).
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN TESTING FUEL SYSTEM PRESSURE.
(1) Remove the protective cap at the fuel rail test
port. Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from gauge set 5069) to the test port pressure
fitting on the fuel rail.
(2) Start the engine and note pressure gauge reading.
Fuel pressure should be 338 kPa 6 14 kPa (49.0
psi +/- 2 psi) at idle.
(3) If pressure is at O psi, connect DRB scan tool
and refer to operating instructions in the appropriate
Powertrain Diagnostics Procedures service manual.
(4) If operating pressure is above 51.0 psi, fuel
pump is OK but pressure regulator is defective. Regulator
is not serviced separately. Replace fuel pump
module assembly.
FUEL PRESSURE LEAK DOWN TEST
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.
(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) Connect the appropriate Fuel Line Pressure
Test Adapter Tool (number 6539, 6631, 6541 or 6923)
between the disconnected fuel line and fuel rail (Fig.
11) or (Fig. 12).
(3) 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.
(4) Start engine and bring to normal operating
temperature.
(5) Observe test gauge. Normal operating pressure
should be 338 kPa 6 14 kPa (49 psi 6 2 psi).
(6) Shut engine off.
(7) Pressure should not fall below 24 psi for five
minutes.
(8) If pressure falls below 24 psi, it must determined
if a fuel injector, the fuel pressure regulator or
a fuel tube/line is leaking.
(9) Again, start engine and bring to normal operating
temperature.
(10) Shut engine off.
(11) Checking for fuel injector 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 24 psi, a fuel injector
or the fuel rail is leaking.
(12) Checking for fuel pump module 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 24 psi, a leak can be found at a fuel tube/
line. If no leaks are found at fuel tubes or lines,
replace the fuel pump module.
"DougW" <post.replies@invalid.address> wrote in message
news:hGpah.43$DF6.28@newsfe24.lga...
> dougguitar@yahoo.com wrote:
>> DougW wrote:
>>> It should hold pressure for over 4-5 hours. Given this and your
>>> 45psi for fuel pressure I'm starting to think the regulator might be
>>> shot. When you take the vac line off see if there is gas dribbling
>>> out.
>>>
>>> --
>>> DougW
>>
>> OK, I timed it. After 4 minutes, the pressure had dropped from around
>> 49 psi to about 35 psi. After 12 minutes, it had dropped to 20 psi. To
>> add to my fun, the 96 GC does not have the fuel pressure regulator
>> attached to the fuel rail: it's built into the fuel pump. @#$%
>> There's just a direct connect fuel line going to the fuel rail.
>>
>> Will a regulator fail in this intermittent way? If that's the case,
>> then I have to pony up the $300 plus for a new fuel pump. Sure wish I
>> could be sure before I make the financial plunge.
>
> Hard to tell, the 96 made a lot of changes and my books are only good
> up to the 95. 49 psi might be normal. Still though I thought pressure
> was supposed to be maintained longer than that. I'd suggest calling a
> dealership and asking if a mechanic could look that up for you. It's
> worth a shot.
>
> I don't think it is your fuel pump. Pumps and pressure regulators
> usually fail to the low pressure side and what you get is a lack of
> power at wide-open-trottle or even pinging.
>
> --
> DougW
>
>
>
11-26-2006, 07:42 PM
#85
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
From the '96 FSM
DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST-4.0L ENGINE
NOTE: The fuel pressure test port is used on certain
engines only. If equipped, the test port will be
located on the fuel rail (Fig. 8). A sealing cap is
screwed onto the test port.
All fuel systems are equipped with a fuel tank module
mounted, fuel pressure regulator. The fuel pressure regulator
is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure
should be 338 kPa 6 14 kPa (49.0 psi 6 2 psi).
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN TESTING FUEL SYSTEM PRESSURE.
(1) Remove the protective cap at the fuel rail test
port. Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from gauge set 5069) to the test port pressure
fitting on the fuel rail.
(2) Start the engine and note pressure gauge reading.
Fuel pressure should be 338 kPa 6 14 kPa (49.0
psi +/- 2 psi) at idle.
(3) If pressure is at O psi, connect DRB scan tool
and refer to operating instructions in the appropriate
Powertrain Diagnostics Procedures service manual.
(4) If operating pressure is above 51.0 psi, fuel
pump is OK but pressure regulator is defective. Regulator
is not serviced separately. Replace fuel pump
module assembly.
FUEL PRESSURE LEAK DOWN TEST
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.
(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) Connect the appropriate Fuel Line Pressure
Test Adapter Tool (number 6539, 6631, 6541 or 6923)
between the disconnected fuel line and fuel rail (Fig.
11) or (Fig. 12).
(3) 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.
(4) Start engine and bring to normal operating
temperature.
(5) Observe test gauge. Normal operating pressure
should be 338 kPa 6 14 kPa (49 psi 6 2 psi).
(6) Shut engine off.
(7) Pressure should not fall below 24 psi for five
minutes.
(8) If pressure falls below 24 psi, it must determined
if a fuel injector, the fuel pressure regulator or
a fuel tube/line is leaking.
(9) Again, start engine and bring to normal operating
temperature.
(10) Shut engine off.
(11) Checking for fuel injector 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 24 psi, a fuel injector
or the fuel rail is leaking.
(12) Checking for fuel pump module 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 24 psi, a leak can be found at a fuel tube/
line. If no leaks are found at fuel tubes or lines,
replace the fuel pump module.
"DougW" <post.replies@invalid.address> wrote in message
news:hGpah.43$DF6.28@newsfe24.lga...
> dougguitar@yahoo.com wrote:
>> DougW wrote:
>>> It should hold pressure for over 4-5 hours. Given this and your
>>> 45psi for fuel pressure I'm starting to think the regulator might be
>>> shot. When you take the vac line off see if there is gas dribbling
>>> out.
>>>
>>> --
>>> DougW
>>
>> OK, I timed it. After 4 minutes, the pressure had dropped from around
>> 49 psi to about 35 psi. After 12 minutes, it had dropped to 20 psi. To
>> add to my fun, the 96 GC does not have the fuel pressure regulator
>> attached to the fuel rail: it's built into the fuel pump. @#$%
>> There's just a direct connect fuel line going to the fuel rail.
>>
>> Will a regulator fail in this intermittent way? If that's the case,
>> then I have to pony up the $300 plus for a new fuel pump. Sure wish I
>> could be sure before I make the financial plunge.
>
> Hard to tell, the 96 made a lot of changes and my books are only good
> up to the 95. 49 psi might be normal. Still though I thought pressure
> was supposed to be maintained longer than that. I'd suggest calling a
> dealership and asking if a mechanic could look that up for you. It's
> worth a shot.
>
> I don't think it is your fuel pump. Pumps and pressure regulators
> usually fail to the low pressure side and what you get is a lack of
> power at wide-open-trottle or even pinging.
>
> --
> DougW
>
>
>
DIAGNOSIS AND TESTING
FUEL PUMP PRESSURE TEST-4.0L ENGINE
NOTE: The fuel pressure test port is used on certain
engines only. If equipped, the test port will be
located on the fuel rail (Fig. 8). A sealing cap is
screwed onto the test port.
All fuel systems are equipped with a fuel tank module
mounted, fuel pressure regulator. The fuel pressure regulator
is not controlled by engine vacuum.
With engine at idle speed, system fuel pressure
should be 338 kPa 6 14 kPa (49.0 psi 6 2 psi).
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL.
WARNING: WEAR PROPER EYE PROTECTION
WHEN TESTING FUEL SYSTEM PRESSURE.
(1) Remove the protective cap at the fuel rail test
port. Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from gauge set 5069) to the test port pressure
fitting on the fuel rail.
(2) Start the engine and note pressure gauge reading.
Fuel pressure should be 338 kPa 6 14 kPa (49.0
psi +/- 2 psi) at idle.
(3) If pressure is at O psi, connect DRB scan tool
and refer to operating instructions in the appropriate
Powertrain Diagnostics Procedures service manual.
(4) If operating pressure is above 51.0 psi, fuel
pump is OK but pressure regulator is defective. Regulator
is not serviced separately. Replace fuel pump
module assembly.
FUEL PRESSURE LEAK DOWN TEST
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.
(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) Connect the appropriate Fuel Line Pressure
Test Adapter Tool (number 6539, 6631, 6541 or 6923)
between the disconnected fuel line and fuel rail (Fig.
11) or (Fig. 12).
(3) 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.
(4) Start engine and bring to normal operating
temperature.
(5) Observe test gauge. Normal operating pressure
should be 338 kPa 6 14 kPa (49 psi 6 2 psi).
(6) Shut engine off.
(7) Pressure should not fall below 24 psi for five
minutes.
(8) If pressure falls below 24 psi, it must determined
if a fuel injector, the fuel pressure regulator or
a fuel tube/line is leaking.
(9) Again, start engine and bring to normal operating
temperature.
(10) Shut engine off.
(11) Checking for fuel injector 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 24 psi, a fuel injector
or the fuel rail is leaking.
(12) Checking for fuel pump module 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 24 psi, a leak can be found at a fuel tube/
line. If no leaks are found at fuel tubes or lines,
replace the fuel pump module.
"DougW" <post.replies@invalid.address> wrote in message
news:hGpah.43$DF6.28@newsfe24.lga...
> dougguitar@yahoo.com wrote:
>> DougW wrote:
>>> It should hold pressure for over 4-5 hours. Given this and your
>>> 45psi for fuel pressure I'm starting to think the regulator might be
>>> shot. When you take the vac line off see if there is gas dribbling
>>> out.
>>>
>>> --
>>> DougW
>>
>> OK, I timed it. After 4 minutes, the pressure had dropped from around
>> 49 psi to about 35 psi. After 12 minutes, it had dropped to 20 psi. To
>> add to my fun, the 96 GC does not have the fuel pressure regulator
>> attached to the fuel rail: it's built into the fuel pump. @#$%
>> There's just a direct connect fuel line going to the fuel rail.
>>
>> Will a regulator fail in this intermittent way? If that's the case,
>> then I have to pony up the $300 plus for a new fuel pump. Sure wish I
>> could be sure before I make the financial plunge.
>
> Hard to tell, the 96 made a lot of changes and my books are only good
> up to the 95. 49 psi might be normal. Still though I thought pressure
> was supposed to be maintained longer than that. I'd suggest calling a
> dealership and asking if a mechanic could look that up for you. It's
> worth a shot.
>
> I don't think it is your fuel pump. Pumps and pressure regulators
> usually fail to the low pressure side and what you get is a lack of
> power at wide-open-trottle or even pinging.
>
> --
> DougW
>
>
>
11-26-2006, 08:31 PM
#86
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
billy ray wrote:
> From the '96 FSM
>
> DIAGNOSIS AND TESTING
>
> FUEL PUMP PRESSURE TEST-4.0L ENGINE
Wow, thanks. At least I now know that 49 psi fuel pressure is correct
for my vehicle. I'll double check it, but I'm pretty sure the pressure
stayed above 24 psi for at least five minutes after shutting off the
engine.
Doug B.
11-26-2006, 08:31 PM
#87
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
billy ray wrote:
> From the '96 FSM
>
> DIAGNOSIS AND TESTING
>
> FUEL PUMP PRESSURE TEST-4.0L ENGINE
Wow, thanks. At least I now know that 49 psi fuel pressure is correct
for my vehicle. I'll double check it, but I'm pretty sure the pressure
stayed above 24 psi for at least five minutes after shutting off the
engine.
Doug B.
11-26-2006, 08:31 PM
#88
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
billy ray wrote:
> From the '96 FSM
>
> DIAGNOSIS AND TESTING
>
> FUEL PUMP PRESSURE TEST-4.0L ENGINE
Wow, thanks. At least I now know that 49 psi fuel pressure is correct
for my vehicle. I'll double check it, but I'm pretty sure the pressure
stayed above 24 psi for at least five minutes after shutting off the
engine.
Doug B.
11-26-2006, 08:39 PM
#89
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
DougW wrote:
> When I was having problems in my 93 I found out the napa part with harness was needed. This was the same coil Jeep installed to
> solve an earlier idle problem. The harness has an internal resistor.
>
> The coil gets 12v from the ASD relay, make sure it's pins are clean. Actually you might swap that relay with the AC or Fog relay
> just to make sure.
> DougW
Doug,
What is the "harness" you're referring to with the coil? The
wiring harness? I'll try swapping out the ASD relay with something
harmless, too.
Thanks again,
Doug B.
11-26-2006, 08:39 PM
#90
Guest
Posts: n/a
Re: 96 Grand Cherokee Stalling
DougW wrote:
> When I was having problems in my 93 I found out the napa part with harness was needed. This was the same coil Jeep installed to
> solve an earlier idle problem. The harness has an internal resistor.
>
> The coil gets 12v from the ASD relay, make sure it's pins are clean. Actually you might swap that relay with the AC or Fog relay
> just to make sure.
> DougW
Doug,
What is the "harness" you're referring to with the coil? The
wiring harness? I'll try swapping out the ASD relay with something
harmless, too.
Thanks again,
Doug B.
