fuel pump problem?
 

I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a dead
start, the vehicle will hesitate for a second or two before it gets going.
After that, it accelerates smoothly and runs strong at high speed. I took it
to the dealer and he said the fuel pump was bad because the pressure was
low. I have read about Jeeps being notorious for bad fuel pumps, but it
seems it usually shows up as hard starting/no starting, rough idle, and/or
stalling out. In fact, I replaced the fuel pump about 4 years ago because it
wouldn't start. It seems to me that if the pressure were low that I would
have other problems like poor performance at high speed. Aside from the
hesitation from a start, it runs fine. I've changed the spark plugs, wires,
fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
passages, and replaced O2 sensor. I've heard there was a TSB about updating
the software in the PCM for a similar problem. The dealer said that it
wasn't necessary, but the PCM has never been updated. Any thoughts?

Re: fuel pump problem?
 

"Martin & Debbie Ghioto" <ghiotom@comcast.net> wrote in message
news:MrFob.58321$ao4.158509@attbi_s51...
> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a
dead
> start, the vehicle will hesitate for a second or two before it gets going.
> After that, it accelerates smoothly and runs strong at high speed. I took
it
> to the dealer and he said the fuel pump was bad because the pressure was
> low. I have read about Jeeps being notorious for bad fuel pumps, but it
> seems it usually shows up as hard starting/no starting, rough idle,
and/or
> stalling out. In fact, I replaced the fuel pump about 4 years ago because
it
> wouldn't start. It seems to me that if the pressure were low that I would
> have other problems like poor performance at high speed. Aside from the
> hesitation from a start, it runs fine. I've changed the spark plugs,
wires,
> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
> passages, and replaced O2 sensor. I've heard there was a TSB about
updating
> the software in the PCM for a similar problem. The dealer said that it
> wasn't necessary, but the PCM has never been updated. Any thoughts?
>
>

A fuel pump won't cause problems taking off from a dead start. the pump runs
at the same speed whether your vehicle is idling or running at WOT. The
excess fuel is returned to the tank via a return line. I would look into the
throttle position sensor either being defective or out of adjustment. I'm
not sure if your vehicle has an adjustment for this or not, but most do. The
sensor also has resistance readings that can be checked with an ohm meter.
Consult a service manual for the readings. The sensor tells the computer
how far the throttle is open and adjusts the injector duty cycle
accordingly. Also, make sure the injector nozzles are spraying a nice even
"fan" pattern. If you see dribbling or an uneven pattern, then there is a
problem with the injectors. the TPS would be my first place to look.

Chris

Re: fuel pump problem?
 

"Martin & Debbie Ghioto" <ghiotom@comcast.net> wrote in message
news:MrFob.58321$ao4.158509@attbi_s51...
> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a
dead
> start, the vehicle will hesitate for a second or two before it gets going.
> After that, it accelerates smoothly and runs strong at high speed. I took
it
> to the dealer and he said the fuel pump was bad because the pressure was
> low. I have read about Jeeps being notorious for bad fuel pumps, but it
> seems it usually shows up as hard starting/no starting, rough idle,
and/or
> stalling out. In fact, I replaced the fuel pump about 4 years ago because
it
> wouldn't start. It seems to me that if the pressure were low that I would
> have other problems like poor performance at high speed. Aside from the
> hesitation from a start, it runs fine. I've changed the spark plugs,
wires,
> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
> passages, and replaced O2 sensor. I've heard there was a TSB about
updating
> the software in the PCM for a similar problem. The dealer said that it
> wasn't necessary, but the PCM has never been updated. Any thoughts?
>
>

A fuel pump won't cause problems taking off from a dead start. the pump runs
at the same speed whether your vehicle is idling or running at WOT. The
excess fuel is returned to the tank via a return line. I would look into the
throttle position sensor either being defective or out of adjustment. I'm
not sure if your vehicle has an adjustment for this or not, but most do. The
sensor also has resistance readings that can be checked with an ohm meter.
Consult a service manual for the readings. The sensor tells the computer
how far the throttle is open and adjusts the injector duty cycle
accordingly. Also, make sure the injector nozzles are spraying a nice even
"fan" pattern. If you see dribbling or an uneven pattern, then there is a
problem with the injectors. the TPS would be my first place to look.

Chris

Re: fuel pump problem?
 

"Martin & Debbie Ghioto" <ghiotom@comcast.net> wrote in message
news:MrFob.58321$ao4.158509@attbi_s51...
> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a
dead
> start, the vehicle will hesitate for a second or two before it gets going.
> After that, it accelerates smoothly and runs strong at high speed. I took
it
> to the dealer and he said the fuel pump was bad because the pressure was
> low. I have read about Jeeps being notorious for bad fuel pumps, but it
> seems it usually shows up as hard starting/no starting, rough idle,
and/or
> stalling out. In fact, I replaced the fuel pump about 4 years ago because
it
> wouldn't start. It seems to me that if the pressure were low that I would
> have other problems like poor performance at high speed. Aside from the
> hesitation from a start, it runs fine. I've changed the spark plugs,
wires,
> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
> passages, and replaced O2 sensor. I've heard there was a TSB about
updating
> the software in the PCM for a similar problem. The dealer said that it
> wasn't necessary, but the PCM has never been updated. Any thoughts?
>
>

A fuel pump won't cause problems taking off from a dead start. the pump runs
at the same speed whether your vehicle is idling or running at WOT. The
excess fuel is returned to the tank via a return line. I would look into the
throttle position sensor either being defective or out of adjustment. I'm
not sure if your vehicle has an adjustment for this or not, but most do. The
sensor also has resistance readings that can be checked with an ohm meter.
Consult a service manual for the readings. The sensor tells the computer
how far the throttle is open and adjusts the injector duty cycle
accordingly. Also, make sure the injector nozzles are spraying a nice even
"fan" pattern. If you see dribbling or an uneven pattern, then there is a
problem with the injectors. the TPS would be my first place to look.

Chris

Re: fuel pump problem?
 

In message <TeGob.91741$832.9298@twister.rdc-kc.rr.com>, "c" wrote:

>
>"Martin & Debbie Ghioto" <ghiotom@comcast.net> wrote in message
>news:MrFob.58321$ao4.158509@attbi_s51...
>> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a
>dead
>> start, the vehicle will hesitate for a second or two before it gets going.
>> After that, it accelerates smoothly and runs strong at high speed. I took
>it
>> to the dealer and he said the fuel pump was bad because the pressure was
>> low. I have read about Jeeps being notorious for bad fuel pumps, but it
>> seems it usually shows up as hard starting/no starting, rough idle,
>and/or
>> stalling out. In fact, I replaced the fuel pump about 4 years ago because
>it
>> wouldn't start. It seems to me that if the pressure were low that I would
>> have other problems like poor performance at high speed. Aside from the
>> hesitation from a start, it runs fine. I've changed the spark plugs,
>wires,
>> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
>> passages, and replaced O2 sensor. I've heard there was a TSB about
>updating
>> the software in the PCM for a similar problem. The dealer said that it
>> wasn't necessary, but the PCM has never been updated. Any thoughts?
>>
>>
>
>A fuel pump won't cause problems taking off from a dead start.

It not only *can* cause this problem, it's fairly common.


the pump runs
>at the same speed whether your vehicle is idling or running at WOT. The
>excess fuel is returned to the tank via a return line. I would look into the
>throttle position sensor either being defective or out of adjustment. I'm
>not sure if your vehicle has an adjustment for this or not, but most do. The
>sensor also has resistance readings that can be checked with an ohm meter.
>Consult a service manual for the readings. The sensor tells the computer
>how far the throttle is open and adjusts the injector duty cycle
>accordingly. Also, make sure the injector nozzles are spraying a nice even
>"fan" pattern. If you see dribbling or an uneven pattern, then there is a
>problem with the injectors. the TPS would be my first place to look.
>
>Chris
>

Re: fuel pump problem?
 

In message <TeGob.91741$832.9298@twister.rdc-kc.rr.com>, "c" wrote:

>
>"Martin & Debbie Ghioto" <ghiotom@comcast.net> wrote in message
>news:MrFob.58321$ao4.158509@attbi_s51...
>> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a
>dead
>> start, the vehicle will hesitate for a second or two before it gets going.
>> After that, it accelerates smoothly and runs strong at high speed. I took
>it
>> to the dealer and he said the fuel pump was bad because the pressure was
>> low. I have read about Jeeps being notorious for bad fuel pumps, but it
>> seems it usually shows up as hard starting/no starting, rough idle,
>and/or
>> stalling out. In fact, I replaced the fuel pump about 4 years ago because
>it
>> wouldn't start. It seems to me that if the pressure were low that I would
>> have other problems like poor performance at high speed. Aside from the
>> hesitation from a start, it runs fine. I've changed the spark plugs,
>wires,
>> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
>> passages, and replaced O2 sensor. I've heard there was a TSB about
>updating
>> the software in the PCM for a similar problem. The dealer said that it
>> wasn't necessary, but the PCM has never been updated. Any thoughts?
>>
>>
>
>A fuel pump won't cause problems taking off from a dead start.

It not only *can* cause this problem, it's fairly common.


the pump runs
>at the same speed whether your vehicle is idling or running at WOT. The
>excess fuel is returned to the tank via a return line. I would look into the
>throttle position sensor either being defective or out of adjustment. I'm
>not sure if your vehicle has an adjustment for this or not, but most do. The
>sensor also has resistance readings that can be checked with an ohm meter.
>Consult a service manual for the readings. The sensor tells the computer
>how far the throttle is open and adjusts the injector duty cycle
>accordingly. Also, make sure the injector nozzles are spraying a nice even
>"fan" pattern. If you see dribbling or an uneven pattern, then there is a
>problem with the injectors. the TPS would be my first place to look.
>
>Chris
>

Re: fuel pump problem?
 

In message <TeGob.91741$832.9298@twister.rdc-kc.rr.com>, "c" wrote:

>
>"Martin & Debbie Ghioto" <ghiotom@comcast.net> wrote in message
>news:MrFob.58321$ao4.158509@attbi_s51...
>> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a
>dead
>> start, the vehicle will hesitate for a second or two before it gets going.
>> After that, it accelerates smoothly and runs strong at high speed. I took
>it
>> to the dealer and he said the fuel pump was bad because the pressure was
>> low. I have read about Jeeps being notorious for bad fuel pumps, but it
>> seems it usually shows up as hard starting/no starting, rough idle,
>and/or
>> stalling out. In fact, I replaced the fuel pump about 4 years ago because
>it
>> wouldn't start. It seems to me that if the pressure were low that I would
>> have other problems like poor performance at high speed. Aside from the
>> hesitation from a start, it runs fine. I've changed the spark plugs,
>wires,
>> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
>> passages, and replaced O2 sensor. I've heard there was a TSB about
>updating
>> the software in the PCM for a similar problem. The dealer said that it
>> wasn't necessary, but the PCM has never been updated. Any thoughts?
>>
>>
>
>A fuel pump won't cause problems taking off from a dead start.

It not only *can* cause this problem, it's fairly common.


the pump runs
>at the same speed whether your vehicle is idling or running at WOT. The
>excess fuel is returned to the tank via a return line. I would look into the
>throttle position sensor either being defective or out of adjustment. I'm
>not sure if your vehicle has an adjustment for this or not, but most do. The
>sensor also has resistance readings that can be checked with an ohm meter.
>Consult a service manual for the readings. The sensor tells the computer
>how far the throttle is open and adjusts the injector duty cycle
>accordingly. Also, make sure the injector nozzles are spraying a nice even
>"fan" pattern. If you see dribbling or an uneven pattern, then there is a
>problem with the injectors. the TPS would be my first place to look.
>
>Chris
>

Re: fuel pump problem?
 

Martin & Debbie Ghioto did pass the time by typing:
> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a dead
> start, the vehicle will hesitate for a second or two before it gets going.
> After that, it accelerates smoothly and runs strong at high speed. I took it
> to the dealer and he said the fuel pump was bad because the pressure was
> low. I have read about Jeeps being notorious for bad fuel pumps, but it
> seems it usually shows up as hard starting/no starting, rough idle, and/or
> stalling out. In fact, I replaced the fuel pump about 4 years ago because it
> wouldn't start. It seems to me that if the pressure were low that I would
> have other problems like poor performance at high speed. Aside from the
> hesitation from a start, it runs fine. I've changed the spark plugs, wires,
> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
> passages, and replaced O2 sensor. I've heard there was a TSB about updating
> the software in the PCM for a similar problem. The dealer said that it
> wasn't necessary, but the PCM has never been updated. Any thoughts?

Clear some things up for me.

- By acccelerate quickly do you mean
WOT (wide open throttle) i.e. mashing the gass, pedal to the metal, etc.
or open throttle, but not mashed all the way down.

- Does this happen more with the vehicle cold or at operating temperature or both.

Not all sensors are used in all conditions. If your O2 sensor hasn't been replaced
you probably should. They tend to fail slowly and as they do it causes your engine
to run richer and richer. Gas mileage and power goes in the crapper.

The MAP (Manifold Air Pressure) sensor will also cause WOT problems.

The sensor diagnostics section on my webpage may help. It's for the
I6 but the basic electronics are identical.

Low fuel pressure can be caused by a faulty pressure regulator or vac leak.

Before replacing any sensor it is best to clean the connectors. Lots of times
a little corrosion is the real problem.

--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors

Re: fuel pump problem?
 

Martin & Debbie Ghioto did pass the time by typing:
> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a dead
> start, the vehicle will hesitate for a second or two before it gets going.
> After that, it accelerates smoothly and runs strong at high speed. I took it
> to the dealer and he said the fuel pump was bad because the pressure was
> low. I have read about Jeeps being notorious for bad fuel pumps, but it
> seems it usually shows up as hard starting/no starting, rough idle, and/or
> stalling out. In fact, I replaced the fuel pump about 4 years ago because it
> wouldn't start. It seems to me that if the pressure were low that I would
> have other problems like poor performance at high speed. Aside from the
> hesitation from a start, it runs fine. I've changed the spark plugs, wires,
> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
> passages, and replaced O2 sensor. I've heard there was a TSB about updating
> the software in the PCM for a similar problem. The dealer said that it
> wasn't necessary, but the PCM has never been updated. Any thoughts?

Clear some things up for me.

- By acccelerate quickly do you mean
WOT (wide open throttle) i.e. mashing the gass, pedal to the metal, etc.
or open throttle, but not mashed all the way down.

- Does this happen more with the vehicle cold or at operating temperature or both.

Not all sensors are used in all conditions. If your O2 sensor hasn't been replaced
you probably should. They tend to fail slowly and as they do it causes your engine
to run richer and richer. Gas mileage and power goes in the crapper.

The MAP (Manifold Air Pressure) sensor will also cause WOT problems.

The sensor diagnostics section on my webpage may help. It's for the
I6 but the basic electronics are identical.

Low fuel pressure can be caused by a faulty pressure regulator or vac leak.

Before replacing any sensor it is best to clean the connectors. Lots of times
a little corrosion is the real problem.

--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors

Re: fuel pump problem?
 

Martin & Debbie Ghioto did pass the time by typing:
> I have a '96 Grand Cherokee w/5.2 V8. When I accelerate quickly from a dead
> start, the vehicle will hesitate for a second or two before it gets going.
> After that, it accelerates smoothly and runs strong at high speed. I took it
> to the dealer and he said the fuel pump was bad because the pressure was
> low. I have read about Jeeps being notorious for bad fuel pumps, but it
> seems it usually shows up as hard starting/no starting, rough idle, and/or
> stalling out. In fact, I replaced the fuel pump about 4 years ago because it
> wouldn't start. It seems to me that if the pressure were low that I would
> have other problems like poor performance at high speed. Aside from the
> hesitation from a start, it runs fine. I've changed the spark plugs, wires,
> fuel filter, air filter, PCV valve, cleaned throttle body, cleaned IAC
> passages, and replaced O2 sensor. I've heard there was a TSB about updating
> the software in the PCM for a similar problem. The dealer said that it
> wasn't necessary, but the PCM has never been updated. Any thoughts?

Clear some things up for me.

- By acccelerate quickly do you mean
WOT (wide open throttle) i.e. mashing the gass, pedal to the metal, etc.
or open throttle, but not mashed all the way down.

- Does this happen more with the vehicle cold or at operating temperature or both.

Not all sensors are used in all conditions. If your O2 sensor hasn't been replaced
you probably should. They tend to fail slowly and as they do it causes your engine
to run richer and richer. Gas mileage and power goes in the crapper.

The MAP (Manifold Air Pressure) sensor will also cause WOT problems.

The sensor diagnostics section on my webpage may help. It's for the
I6 but the basic electronics are identical.

Low fuel pressure can be caused by a faulty pressure regulator or vac leak.

Before replacing any sensor it is best to clean the connectors. Lots of times
a little corrosion is the real problem.

--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors