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.

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
http://www.billhughes.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.

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) Hughes III" > wrote in message
...
> 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
> http://www.billhughes.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.

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) Hughes III" > wrote in message
> ...
> > 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
> > http://www.billhughes.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.

Every thing you say sounds like a dragging or gummed up switch or
relay, unlikely as that may be, or pehaps a bad contact in one of
them. I'd be looking at the ignition switch circuit beginning right
at the switch output to see if the voltage delays there then following
it on through the power distibution system to see just where the delay
was. Cheap voltmeter and some patience.

On Tue, 6 Jun 2006 02:35:51 UTC "iPlay1515" >
wrote:

> 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) Hughes III" > wrote in message
> > ...
> > > 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
> > > http://www.billhughes.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.
>


--
Will Honea

Thanks.

I've tested the relevent circuits with a voltmeter and test light and
found no delays or problems up to the point/circuit where the PCM
(computer) energizes/controls the fuel pump relay. The voltage at this
point follows the exact delays/symptoms as described in my original
post. When the fuel pump relay is energized by the PCM, the pump always
runs and produces the correct pressure. The delays are comming from the
PCM.


The fuel pump delay problem is very repeatable and predictable and is
not intermittent. When the engine is cold, there is a delay, when the
engine is hot, there is no delay. When the engine is warm, the delay
time varies depending on how warm the engine is.



Will Honea wrote:
> Every thing you say sounds like a dragging or gummed up switch or
> relay, unlikely as that may be, or pehaps a bad contact in one of
> them. I'd be looking at the ignition switch circuit beginning right
> at the switch output to see if the voltage delays there then following
> it on through the power distibution system to see just where the delay
> was. Cheap voltmeter and some patience.
>
> On Tue, 6 Jun 2006 02:35:51 UTC "iPlay1515" >
> wrote:
>
> > 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) Hughes III" > wrote in message
> > > ...
> > > > 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
> > > > http://www.billhughes.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.
> >
>
>
> --
> Will Honea

Those ISO relays are pretty cheap. Get a new one and see if that is it.
Look under the relay to make sure the socket is not crudded up, if it
is, a relay burnisher works. Don't use sandpaper, but you can make a
burnisher out of one of those small diamond style fingernail files and a
Dremel if you can't find the real one locally.

Then take your current relay and cut the top off. You can use it as a
diagnostic for all sorts of stuff by sticking it in any relay socket and
having someone close it for you manually. Helped me find a bad ignition
switch the local parts folks swore never failed.



Will Honea proclaimed:

> Every thing you say sounds like a dragging or gummed up switch or
> relay, unlikely as that may be, or pehaps a bad contact in one of
> them. I'd be looking at the ignition switch circuit beginning right
> at the switch output to see if the voltage delays there then following
> it on through the power distibution system to see just where the delay
> was. Cheap voltmeter and some patience.
>
> On Tue, 6 Jun 2006 02:35:51 UTC "iPlay1515" >
> wrote:
>
>
>>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) Hughes III" > wrote in message
...
>>>
>>>> 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
http://www.billhughes.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.
>>
>
>