Fuel Pump Delay When Cold
 

Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles

Engine codes: 12, 55 (using check engine light blinking)


Note: The engine is never started during the following tests except
where indicated:

Normally when I switch the ignition on, my fuel pump will operate for
about 1.5 seconds and stop. This charges the fuel rail with about 40
psi.

Recently, I noticed that the vehicle has become harder/longer to start,
but only when cold.

I've noticed that the fuel pump does not run immediately when I switch
on the ignition, but there is a delay up to 30-40 sec. when the engine
is cold. I've also noticed that the "check engine" light is also
delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
cold.

I've check the fuel rail pressure with a gauge, and once the fuel pump
runs (after the delay), the pressure is good (40 psi).

I removed the plastic cover from the fuel pump relay and the fuel pump
will run each and every time I manually activate the relay regardless
of temperature. I've replaced this relay with no change in symptoms.

After the initial 20-30 sec. period, the fuel pump will operated for
1.5 sec. each time the ignition switch is cycled from off to on.
However, if the engine is cold and I wait 10 - 15 sec. between each
off-on cycle of the ignition switch, the fuel pump delay begins to
surface again (2-4 sec delay). The longer I wait between off-on cycles
of the switch, the greater the delay for the fuel pump.

Now if I start the engine and let it run for 120 sec., there is no fuel
pump delay. However, if I allow the engine to remain off/cool for 120
sec, the delay begins to re-appear but with a shorter delay of only
6-10 sec. The longer the engine is allow to cool, the longer the
delay.

I suspect that I have a sensor that is failing and that it is
temperature sensitive, and this sensor is affecting the operation of
the PCM with respect to the initial operation of the fuel pump.


My O2 sensor is a 4 wire device, which I believe indicates it has an
internal heater. It's the original sensor. I haven't changed it due to
the replacement cost, but I am beginning to suspect that it may be
contributing to the fuel pump delay symptoms. I don't know if an O2
sensor can produces the above symptoms.

Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

I think your describing a bad fuel pump, and you've got about fifty
thousand more than others get. Maybe in another test have a friend kick
the tank.
Also your pressure regulator and fuel return could be bleeding off
early, and it also controls fuel pressure via sensing your vacuum,
pictured at:
http://members.cox.net/wilsond/Fixes...tml#fuelsystem
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/


TheLegMan@gmail.com wrote:
>
> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
>
> Engine codes: 12, 55 (using check engine light blinking)
>
> Note: The engine is never started during the following tests except
> where indicated:
>
> Normally when I switch the ignition on, my fuel pump will operate for
> about 1.5 seconds and stop. This charges the fuel rail with about 40
> psi.
>
> Recently, I noticed that the vehicle has become harder/longer to start,
> but only when cold.
>
> I've noticed that the fuel pump does not run immediately when I switch
> on the ignition, but there is a delay up to 30-40 sec. when the engine
> is cold. I've also noticed that the "check engine" light is also
> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
> cold.
>
> I've check the fuel rail pressure with a gauge, and once the fuel pump
> runs (after the delay), the pressure is good (40 psi).
>
> I removed the plastic cover from the fuel pump relay and the fuel pump
> will run each and every time I manually activate the relay regardless
> of temperature. I've replaced this relay with no change in symptoms.
>
> After the initial 20-30 sec. period, the fuel pump will operated for
> 1.5 sec. each time the ignition switch is cycled from off to on.
> However, if the engine is cold and I wait 10 - 15 sec. between each
> off-on cycle of the ignition switch, the fuel pump delay begins to
> surface again (2-4 sec delay). The longer I wait between off-on cycles
> of the switch, the greater the delay for the fuel pump.
>
> Now if I start the engine and let it run for 120 sec., there is no fuel
> pump delay. However, if I allow the engine to remain off/cool for 120
> sec, the delay begins to re-appear but with a shorter delay of only
> 6-10 sec. The longer the engine is allow to cool, the longer the
> delay.
>
> I suspect that I have a sensor that is failing and that it is
> temperature sensitive, and this sensor is affecting the operation of
> the PCM with respect to the initial operation of the fuel pump.
>
> My O2 sensor is a 4 wire device, which I believe indicates it has an
> internal heater. It's the original sensor. I haven't changed it due to
> the replacement cost, but I am beginning to suspect that it may be
> contributing to the fuel pump delay symptoms. I don't know if an O2
> sensor can produces the above symptoms.
>
> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

I think your describing a bad fuel pump, and you've got about fifty
thousand more than others get. Maybe in another test have a friend kick
the tank.
Also your pressure regulator and fuel return could be bleeding off
early, and it also controls fuel pressure via sensing your vacuum,
pictured at:
http://members.cox.net/wilsond/Fixes...tml#fuelsystem
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/


TheLegMan@gmail.com wrote:
>
> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
>
> Engine codes: 12, 55 (using check engine light blinking)
>
> Note: The engine is never started during the following tests except
> where indicated:
>
> Normally when I switch the ignition on, my fuel pump will operate for
> about 1.5 seconds and stop. This charges the fuel rail with about 40
> psi.
>
> Recently, I noticed that the vehicle has become harder/longer to start,
> but only when cold.
>
> I've noticed that the fuel pump does not run immediately when I switch
> on the ignition, but there is a delay up to 30-40 sec. when the engine
> is cold. I've also noticed that the "check engine" light is also
> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
> cold.
>
> I've check the fuel rail pressure with a gauge, and once the fuel pump
> runs (after the delay), the pressure is good (40 psi).
>
> I removed the plastic cover from the fuel pump relay and the fuel pump
> will run each and every time I manually activate the relay regardless
> of temperature. I've replaced this relay with no change in symptoms.
>
> After the initial 20-30 sec. period, the fuel pump will operated for
> 1.5 sec. each time the ignition switch is cycled from off to on.
> However, if the engine is cold and I wait 10 - 15 sec. between each
> off-on cycle of the ignition switch, the fuel pump delay begins to
> surface again (2-4 sec delay). The longer I wait between off-on cycles
> of the switch, the greater the delay for the fuel pump.
>
> Now if I start the engine and let it run for 120 sec., there is no fuel
> pump delay. However, if I allow the engine to remain off/cool for 120
> sec, the delay begins to re-appear but with a shorter delay of only
> 6-10 sec. The longer the engine is allow to cool, the longer the
> delay.
>
> I suspect that I have a sensor that is failing and that it is
> temperature sensitive, and this sensor is affecting the operation of
> the PCM with respect to the initial operation of the fuel pump.
>
> My O2 sensor is a 4 wire device, which I believe indicates it has an
> internal heater. It's the original sensor. I haven't changed it due to
> the replacement cost, but I am beginning to suspect that it may be
> contributing to the fuel pump delay symptoms. I don't know if an O2
> sensor can produces the above symptoms.
>
> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

I think your describing a bad fuel pump, and you've got about fifty
thousand more than others get. Maybe in another test have a friend kick
the tank.
Also your pressure regulator and fuel return could be bleeding off
early, and it also controls fuel pressure via sensing your vacuum,
pictured at:
http://members.cox.net/wilsond/Fixes...tml#fuelsystem
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/


TheLegMan@gmail.com wrote:
>
> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
>
> Engine codes: 12, 55 (using check engine light blinking)
>
> Note: The engine is never started during the following tests except
> where indicated:
>
> Normally when I switch the ignition on, my fuel pump will operate for
> about 1.5 seconds and stop. This charges the fuel rail with about 40
> psi.
>
> Recently, I noticed that the vehicle has become harder/longer to start,
> but only when cold.
>
> I've noticed that the fuel pump does not run immediately when I switch
> on the ignition, but there is a delay up to 30-40 sec. when the engine
> is cold. I've also noticed that the "check engine" light is also
> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
> cold.
>
> I've check the fuel rail pressure with a gauge, and once the fuel pump
> runs (after the delay), the pressure is good (40 psi).
>
> I removed the plastic cover from the fuel pump relay and the fuel pump
> will run each and every time I manually activate the relay regardless
> of temperature. I've replaced this relay with no change in symptoms.
>
> After the initial 20-30 sec. period, the fuel pump will operated for
> 1.5 sec. each time the ignition switch is cycled from off to on.
> However, if the engine is cold and I wait 10 - 15 sec. between each
> off-on cycle of the ignition switch, the fuel pump delay begins to
> surface again (2-4 sec delay). The longer I wait between off-on cycles
> of the switch, the greater the delay for the fuel pump.
>
> Now if I start the engine and let it run for 120 sec., there is no fuel
> pump delay. However, if I allow the engine to remain off/cool for 120
> sec, the delay begins to re-appear but with a shorter delay of only
> 6-10 sec. The longer the engine is allow to cool, the longer the
> delay.
>
> I suspect that I have a sensor that is failing and that it is
> temperature sensitive, and this sensor is affecting the operation of
> the PCM with respect to the initial operation of the fuel pump.
>
> My O2 sensor is a 4 wire device, which I believe indicates it has an
> internal heater. It's the original sensor. I haven't changed it due to
> the replacement cost, but I am beginning to suspect that it may be
> contributing to the fuel pump delay symptoms. I don't know if an O2
> sensor can produces the above symptoms.
>
> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

I agree with Bill it is either a bad fuel pump or the fuel pump check valve.
Try this test, when cold over night turn on vehicle for 20 seconds but do
not start, do this 3 times on the 4th time start the vehicle if it starts
immediately it is more than likely the check valve.
Coasty


"L.W.(Bill) ------ III" <----------@cox.net> wrote in message
news:44847150.9087E63@cox.net...
> I think your describing a bad fuel pump, and you've got about fifty
> thousand more than others get. Maybe in another test have a friend kick
> the tank.
> Also your pressure regulator and fuel return could be bleeding off
> early, and it also controls fuel pressure via sensing your vacuum,
> pictured at:
> http://members.cox.net/wilsond/Fixes...tml#fuelsystem
> God Bless America, Bill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
>
> TheLegMan@gmail.com wrote:
>>
>> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
>>
>> Engine codes: 12, 55 (using check engine light blinking)
>>
>> Note: The engine is never started during the following tests except
>> where indicated:
>>
>> Normally when I switch the ignition on, my fuel pump will operate for
>> about 1.5 seconds and stop. This charges the fuel rail with about 40
>> psi.
>>
>> Recently, I noticed that the vehicle has become harder/longer to start,
>> but only when cold.
>>
>> I've noticed that the fuel pump does not run immediately when I switch
>> on the ignition, but there is a delay up to 30-40 sec. when the engine
>> is cold. I've also noticed that the "check engine" light is also
>> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
>> cold.
>>
>> I've check the fuel rail pressure with a gauge, and once the fuel pump
>> runs (after the delay), the pressure is good (40 psi).
>>
>> I removed the plastic cover from the fuel pump relay and the fuel pump
>> will run each and every time I manually activate the relay regardless
>> of temperature. I've replaced this relay with no change in symptoms.
>>
>> After the initial 20-30 sec. period, the fuel pump will operated for
>> 1.5 sec. each time the ignition switch is cycled from off to on.
>> However, if the engine is cold and I wait 10 - 15 sec. between each
>> off-on cycle of the ignition switch, the fuel pump delay begins to
>> surface again (2-4 sec delay). The longer I wait between off-on cycles
>> of the switch, the greater the delay for the fuel pump.
>>
>> Now if I start the engine and let it run for 120 sec., there is no fuel
>> pump delay. However, if I allow the engine to remain off/cool for 120
>> sec, the delay begins to re-appear but with a shorter delay of only
>> 6-10 sec. The longer the engine is allow to cool, the longer the
>> delay.
>>
>> I suspect that I have a sensor that is failing and that it is
>> temperature sensitive, and this sensor is affecting the operation of
>> the PCM with respect to the initial operation of the fuel pump.
>>
>> My O2 sensor is a 4 wire device, which I believe indicates it has an
>> internal heater. It's the original sensor. I haven't changed it due to
>> the replacement cost, but I am beginning to suspect that it may be
>> contributing to the fuel pump delay symptoms. I don't know if an O2
>> sensor can produces the above symptoms.
>>
>> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

I agree with Bill it is either a bad fuel pump or the fuel pump check valve.
Try this test, when cold over night turn on vehicle for 20 seconds but do
not start, do this 3 times on the 4th time start the vehicle if it starts
immediately it is more than likely the check valve.
Coasty


"L.W.(Bill) ------ III" <----------@cox.net> wrote in message
news:44847150.9087E63@cox.net...
> I think your describing a bad fuel pump, and you've got about fifty
> thousand more than others get. Maybe in another test have a friend kick
> the tank.
> Also your pressure regulator and fuel return could be bleeding off
> early, and it also controls fuel pressure via sensing your vacuum,
> pictured at:
> http://members.cox.net/wilsond/Fixes...tml#fuelsystem
> God Bless America, Bill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
>
> TheLegMan@gmail.com wrote:
>>
>> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
>>
>> Engine codes: 12, 55 (using check engine light blinking)
>>
>> Note: The engine is never started during the following tests except
>> where indicated:
>>
>> Normally when I switch the ignition on, my fuel pump will operate for
>> about 1.5 seconds and stop. This charges the fuel rail with about 40
>> psi.
>>
>> Recently, I noticed that the vehicle has become harder/longer to start,
>> but only when cold.
>>
>> I've noticed that the fuel pump does not run immediately when I switch
>> on the ignition, but there is a delay up to 30-40 sec. when the engine
>> is cold. I've also noticed that the "check engine" light is also
>> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
>> cold.
>>
>> I've check the fuel rail pressure with a gauge, and once the fuel pump
>> runs (after the delay), the pressure is good (40 psi).
>>
>> I removed the plastic cover from the fuel pump relay and the fuel pump
>> will run each and every time I manually activate the relay regardless
>> of temperature. I've replaced this relay with no change in symptoms.
>>
>> After the initial 20-30 sec. period, the fuel pump will operated for
>> 1.5 sec. each time the ignition switch is cycled from off to on.
>> However, if the engine is cold and I wait 10 - 15 sec. between each
>> off-on cycle of the ignition switch, the fuel pump delay begins to
>> surface again (2-4 sec delay). The longer I wait between off-on cycles
>> of the switch, the greater the delay for the fuel pump.
>>
>> Now if I start the engine and let it run for 120 sec., there is no fuel
>> pump delay. However, if I allow the engine to remain off/cool for 120
>> sec, the delay begins to re-appear but with a shorter delay of only
>> 6-10 sec. The longer the engine is allow to cool, the longer the
>> delay.
>>
>> I suspect that I have a sensor that is failing and that it is
>> temperature sensitive, and this sensor is affecting the operation of
>> the PCM with respect to the initial operation of the fuel pump.
>>
>> My O2 sensor is a 4 wire device, which I believe indicates it has an
>> internal heater. It's the original sensor. I haven't changed it due to
>> the replacement cost, but I am beginning to suspect that it may be
>> contributing to the fuel pump delay symptoms. I don't know if an O2
>> sensor can produces the above symptoms.
>>
>> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

I agree with Bill it is either a bad fuel pump or the fuel pump check valve.
Try this test, when cold over night turn on vehicle for 20 seconds but do
not start, do this 3 times on the 4th time start the vehicle if it starts
immediately it is more than likely the check valve.
Coasty


"L.W.(Bill) ------ III" <----------@cox.net> wrote in message
news:44847150.9087E63@cox.net...
> I think your describing a bad fuel pump, and you've got about fifty
> thousand more than others get. Maybe in another test have a friend kick
> the tank.
> Also your pressure regulator and fuel return could be bleeding off
> early, and it also controls fuel pressure via sensing your vacuum,
> pictured at:
> http://members.cox.net/wilsond/Fixes...tml#fuelsystem
> God Bless America, Bill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
>
> TheLegMan@gmail.com wrote:
>>
>> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
>>
>> Engine codes: 12, 55 (using check engine light blinking)
>>
>> Note: The engine is never started during the following tests except
>> where indicated:
>>
>> Normally when I switch the ignition on, my fuel pump will operate for
>> about 1.5 seconds and stop. This charges the fuel rail with about 40
>> psi.
>>
>> Recently, I noticed that the vehicle has become harder/longer to start,
>> but only when cold.
>>
>> I've noticed that the fuel pump does not run immediately when I switch
>> on the ignition, but there is a delay up to 30-40 sec. when the engine
>> is cold. I've also noticed that the "check engine" light is also
>> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
>> cold.
>>
>> I've check the fuel rail pressure with a gauge, and once the fuel pump
>> runs (after the delay), the pressure is good (40 psi).
>>
>> I removed the plastic cover from the fuel pump relay and the fuel pump
>> will run each and every time I manually activate the relay regardless
>> of temperature. I've replaced this relay with no change in symptoms.
>>
>> After the initial 20-30 sec. period, the fuel pump will operated for
>> 1.5 sec. each time the ignition switch is cycled from off to on.
>> However, if the engine is cold and I wait 10 - 15 sec. between each
>> off-on cycle of the ignition switch, the fuel pump delay begins to
>> surface again (2-4 sec delay). The longer I wait between off-on cycles
>> of the switch, the greater the delay for the fuel pump.
>>
>> Now if I start the engine and let it run for 120 sec., there is no fuel
>> pump delay. However, if I allow the engine to remain off/cool for 120
>> sec, the delay begins to re-appear but with a shorter delay of only
>> 6-10 sec. The longer the engine is allow to cool, the longer the
>> delay.
>>
>> I suspect that I have a sensor that is failing and that it is
>> temperature sensitive, and this sensor is affecting the operation of
>> the PCM with respect to the initial operation of the fuel pump.
>>
>> My O2 sensor is a 4 wire device, which I believe indicates it has an
>> internal heater. It's the original sensor. I haven't changed it due to
>> the replacement cost, but I am beginning to suspect that it may be
>> contributing to the fuel pump delay symptoms. I don't know if an O2
>> sensor can produces the above symptoms.
>>
>> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

Thanks guys. The fuel pump was replaced about 50k miles back, and it
runs great when I manually engage the fuel pump control relay. It
doesn't matter if it's hot, cold, or warm, the pump always runs ok when
I close the relay by hand. The fuel pressure is always in spec when the
pump is running.

The problem still seems to be related to the signal from the computer
which energizes the fuel pump relay.

When I run the fuel pump manually, it builds to the correct pressure
(40 psi) and holds the pressure after the pump stops. It bleeds off
very slowly when the pump isn't running.



Coasty wrote:
> I agree with Bill it is either a bad fuel pump or the fuel pump check valve.
> Try this test, when cold over night turn on vehicle for 20 seconds but do
> not start, do this 3 times on the 4th time start the vehicle if it starts
> immediately it is more than likely the check valve.
> Coasty
>
>
> "L.W.(Bill) ------ III" <----------@cox.net> wrote in message
> news:44847150.9087E63@cox.net...
> > I think your describing a bad fuel pump, and you've got about fifty
> > thousand more than others get. Maybe in another test have a friend kick
> > the tank.
> > Also your pressure regulator and fuel return could be bleeding off
> > early, and it also controls fuel pressure via sensing your vacuum,
> > pictured at:
> > http://members.cox.net/wilsond/Fixes...tml#fuelsystem
> > God Bless America, Bill O|||||||O
> > mailto:-------------------- http://www.----------.com/
> >
> >
> > TheLegMan@gmail.com wrote:
> >>
> >> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
> >>
> >> Engine codes: 12, 55 (using check engine light blinking)
> >>
> >> Note: The engine is never started during the following tests except
> >> where indicated:
> >>
> >> Normally when I switch the ignition on, my fuel pump will operate for
> >> about 1.5 seconds and stop. This charges the fuel rail with about 40
> >> psi.
> >>
> >> Recently, I noticed that the vehicle has become harder/longer to start,
> >> but only when cold.
> >>
> >> I've noticed that the fuel pump does not run immediately when I switch
> >> on the ignition, but there is a delay up to 30-40 sec. when the engine
> >> is cold. I've also noticed that the "check engine" light is also
> >> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
> >> cold.
> >>
> >> I've check the fuel rail pressure with a gauge, and once the fuel pump
> >> runs (after the delay), the pressure is good (40 psi).
> >>
> >> I removed the plastic cover from the fuel pump relay and the fuel pump
> >> will run each and every time I manually activate the relay regardless
> >> of temperature. I've replaced this relay with no change in symptoms.
> >>
> >> After the initial 20-30 sec. period, the fuel pump will operated for
> >> 1.5 sec. each time the ignition switch is cycled from off to on.
> >> However, if the engine is cold and I wait 10 - 15 sec. between each
> >> off-on cycle of the ignition switch, the fuel pump delay begins to
> >> surface again (2-4 sec delay). The longer I wait between off-on cycles
> >> of the switch, the greater the delay for the fuel pump.
> >>
> >> Now if I start the engine and let it run for 120 sec., there is no fuel
> >> pump delay. However, if I allow the engine to remain off/cool for 120
> >> sec, the delay begins to re-appear but with a shorter delay of only
> >> 6-10 sec. The longer the engine is allow to cool, the longer the
> >> delay.
> >>
> >> I suspect that I have a sensor that is failing and that it is
> >> temperature sensitive, and this sensor is affecting the operation of
> >> the PCM with respect to the initial operation of the fuel pump.
> >>
> >> My O2 sensor is a 4 wire device, which I believe indicates it has an
> >> internal heater. It's the original sensor. I haven't changed it due to
> >> the replacement cost, but I am beginning to suspect that it may be
> >> contributing to the fuel pump delay symptoms. I don't know if an O2
> >> sensor can produces the above symptoms.
> >>
> >> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

Thanks guys. The fuel pump was replaced about 50k miles back, and it
runs great when I manually engage the fuel pump control relay. It
doesn't matter if it's hot, cold, or warm, the pump always runs ok when
I close the relay by hand. The fuel pressure is always in spec when the
pump is running.

The problem still seems to be related to the signal from the computer
which energizes the fuel pump relay.

When I run the fuel pump manually, it builds to the correct pressure
(40 psi) and holds the pressure after the pump stops. It bleeds off
very slowly when the pump isn't running.



Coasty wrote:
> I agree with Bill it is either a bad fuel pump or the fuel pump check valve.
> Try this test, when cold over night turn on vehicle for 20 seconds but do
> not start, do this 3 times on the 4th time start the vehicle if it starts
> immediately it is more than likely the check valve.
> Coasty
>
>
> "L.W.(Bill) ------ III" <----------@cox.net> wrote in message
> news:44847150.9087E63@cox.net...
> > I think your describing a bad fuel pump, and you've got about fifty
> > thousand more than others get. Maybe in another test have a friend kick
> > the tank.
> > Also your pressure regulator and fuel return could be bleeding off
> > early, and it also controls fuel pressure via sensing your vacuum,
> > pictured at:
> > http://members.cox.net/wilsond/Fixes...tml#fuelsystem
> > God Bless America, Bill O|||||||O
> > mailto:-------------------- http://www.----------.com/
> >
> >
> > TheLegMan@gmail.com wrote:
> >>
> >> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
> >>
> >> Engine codes: 12, 55 (using check engine light blinking)
> >>
> >> Note: The engine is never started during the following tests except
> >> where indicated:
> >>
> >> Normally when I switch the ignition on, my fuel pump will operate for
> >> about 1.5 seconds and stop. This charges the fuel rail with about 40
> >> psi.
> >>
> >> Recently, I noticed that the vehicle has become harder/longer to start,
> >> but only when cold.
> >>
> >> I've noticed that the fuel pump does not run immediately when I switch
> >> on the ignition, but there is a delay up to 30-40 sec. when the engine
> >> is cold. I've also noticed that the "check engine" light is also
> >> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
> >> cold.
> >>
> >> I've check the fuel rail pressure with a gauge, and once the fuel pump
> >> runs (after the delay), the pressure is good (40 psi).
> >>
> >> I removed the plastic cover from the fuel pump relay and the fuel pump
> >> will run each and every time I manually activate the relay regardless
> >> of temperature. I've replaced this relay with no change in symptoms.
> >>
> >> After the initial 20-30 sec. period, the fuel pump will operated for
> >> 1.5 sec. each time the ignition switch is cycled from off to on.
> >> However, if the engine is cold and I wait 10 - 15 sec. between each
> >> off-on cycle of the ignition switch, the fuel pump delay begins to
> >> surface again (2-4 sec delay). The longer I wait between off-on cycles
> >> of the switch, the greater the delay for the fuel pump.
> >>
> >> Now if I start the engine and let it run for 120 sec., there is no fuel
> >> pump delay. However, if I allow the engine to remain off/cool for 120
> >> sec, the delay begins to re-appear but with a shorter delay of only
> >> 6-10 sec. The longer the engine is allow to cool, the longer the
> >> delay.
> >>
> >> I suspect that I have a sensor that is failing and that it is
> >> temperature sensitive, and this sensor is affecting the operation of
> >> the PCM with respect to the initial operation of the fuel pump.
> >>
> >> My O2 sensor is a 4 wire device, which I believe indicates it has an
> >> internal heater. It's the original sensor. I haven't changed it due to
> >> the replacement cost, but I am beginning to suspect that it may be
> >> contributing to the fuel pump delay symptoms. I don't know if an O2
> >> sensor can produces the above symptoms.
> >>
> >> Your comments, advice, etc. are appreciated.

Re: Fuel Pump Delay When Cold
 

Thanks guys. The fuel pump was replaced about 50k miles back, and it
runs great when I manually engage the fuel pump control relay. It
doesn't matter if it's hot, cold, or warm, the pump always runs ok when
I close the relay by hand. The fuel pressure is always in spec when the
pump is running.

The problem still seems to be related to the signal from the computer
which energizes the fuel pump relay.

When I run the fuel pump manually, it builds to the correct pressure
(40 psi) and holds the pressure after the pump stops. It bleeds off
very slowly when the pump isn't running.



Coasty wrote:
> I agree with Bill it is either a bad fuel pump or the fuel pump check valve.
> Try this test, when cold over night turn on vehicle for 20 seconds but do
> not start, do this 3 times on the 4th time start the vehicle if it starts
> immediately it is more than likely the check valve.
> Coasty
>
>
> "L.W.(Bill) ------ III" <----------@cox.net> wrote in message
> news:44847150.9087E63@cox.net...
> > I think your describing a bad fuel pump, and you've got about fifty
> > thousand more than others get. Maybe in another test have a friend kick
> > the tank.
> > Also your pressure regulator and fuel return could be bleeding off
> > early, and it also controls fuel pressure via sensing your vacuum,
> > pictured at:
> > http://members.cox.net/wilsond/Fixes...tml#fuelsystem
> > God Bless America, Bill O|||||||O
> > mailto:-------------------- http://www.----------.com/
> >
> >
> > TheLegMan@gmail.com wrote:
> >>
> >> Vehicle: 1993 Grand Laredo 4.0, 4wd, Automatic, Air 170,000 miles
> >>
> >> Engine codes: 12, 55 (using check engine light blinking)
> >>
> >> Note: The engine is never started during the following tests except
> >> where indicated:
> >>
> >> Normally when I switch the ignition on, my fuel pump will operate for
> >> about 1.5 seconds and stop. This charges the fuel rail with about 40
> >> psi.
> >>
> >> Recently, I noticed that the vehicle has become harder/longer to start,
> >> but only when cold.
> >>
> >> I've noticed that the fuel pump does not run immediately when I switch
> >> on the ignition, but there is a delay up to 30-40 sec. when the engine
> >> is cold. I've also noticed that the "check engine" light is also
> >> delayed by the same amount as the initial 1.5 sec. fuel pump cycle when
> >> cold.
> >>
> >> I've check the fuel rail pressure with a gauge, and once the fuel pump
> >> runs (after the delay), the pressure is good (40 psi).
> >>
> >> I removed the plastic cover from the fuel pump relay and the fuel pump
> >> will run each and every time I manually activate the relay regardless
> >> of temperature. I've replaced this relay with no change in symptoms.
> >>
> >> After the initial 20-30 sec. period, the fuel pump will operated for
> >> 1.5 sec. each time the ignition switch is cycled from off to on.
> >> However, if the engine is cold and I wait 10 - 15 sec. between each
> >> off-on cycle of the ignition switch, the fuel pump delay begins to
> >> surface again (2-4 sec delay). The longer I wait between off-on cycles
> >> of the switch, the greater the delay for the fuel pump.
> >>
> >> Now if I start the engine and let it run for 120 sec., there is no fuel
> >> pump delay. However, if I allow the engine to remain off/cool for 120
> >> sec, the delay begins to re-appear but with a shorter delay of only
> >> 6-10 sec. The longer the engine is allow to cool, the longer the
> >> delay.
> >>
> >> I suspect that I have a sensor that is failing and that it is
> >> temperature sensitive, and this sensor is affecting the operation of
> >> the PCM with respect to the initial operation of the fuel pump.
> >>
> >> My O2 sensor is a 4 wire device, which I believe indicates it has an
> >> internal heater. It's the original sensor. I haven't changed it due to
> >> the replacement cost, but I am beginning to suspect that it may be
> >> contributing to the fuel pump delay symptoms. I don't know if an O2
> >> sensor can produces the above symptoms.
> >>
> >> Your comments, advice, etc. are appreciated.