Fuel rail pressure sensor question
05-07-2015, 05:47 PM
#1
Fuel rail pressure sensor question
Should the idle change at all when you unplug the fuel rail pressure sensor? '04 FX4 5.4 Been chasing a rough idle for some time now and a strange starting problem when warmed up. Truck either starts immediately almost with no initial cranking of engine, very strange and hard to explain, just starts without a noticable crank or cranks longer than usual but still starts. Im just poking around at this point and noticed there was no idle change when I unplugged the fuel rail connector. Just wanted to know if it was normal
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o6S1D9e (12-05-2021)
05-08-2015, 04:56 AM
#2
Moderator (Ret.)
Eventually, the engine should stumble and stall. That sensor is used to inform the PCM/ECU that pressure at the fuel rails is there, which in turn is used to inform the FPRM (fuel pressure regulator module; the one by the spare tire that has been known to fail due to corrosion) to turn on/off the fuel pump in the fuel tank.
The following users liked this post:
o6S1D9e (12-05-2021)
The following users liked this post:
o6S1D9e (12-05-2021)
05-08-2015, 07:36 AM
#4
Moderator (Ret.)
The warmed engine "immediate start" or "takes longer to start" has me thinking that the PCM/ECU is not getting the correct engine temp reading. On a detected cold engine, the fuel to air mixture is set higher (fuel) to get a cold engine to start, simular to the days of a choke; the choke would cut off air, and allow the fuel mix to be greater.
Once the engine reaches a certain temp, the fuel mixture is lowered, allowing the engine to return to a normal set idle.
Usually an engine today has two temp devices: a temperature sender, used by the cluster temp guage, and a temperature sensor, used by the PCM/ECU to aid in the adjustment of the fuel to air mapping.
My Ford Ranger had this setup, but not sure if these 4.2/4.6/5.4 engines have two temp devices. Perhaps someone else can chime in.
Once the engine reaches a certain temp, the fuel mixture is lowered, allowing the engine to return to a normal set idle.
Usually an engine today has two temp devices: a temperature sender, used by the cluster temp guage, and a temperature sensor, used by the PCM/ECU to aid in the adjustment of the fuel to air mapping.
My Ford Ranger had this setup, but not sure if these 4.2/4.6/5.4 engines have two temp devices. Perhaps someone else can chime in.
05-08-2015, 08:34 AM
#5
Mark
iTrader: (1)
Eventually, the engine should stumble and stall. That sensor is used to inform the PCM/ECU that pressure at the fuel rails is there, which in turn is used to inform the FPRM (fuel pressure regulator module; the one by the spare tire that has been known to fail due to corrosion) to turn on/off the fuel pump in the fuel tank.
05-08-2015, 10:04 AM
#6
Moderator (Ret.)
It's Friday...I need to drink more.
I've yet to have an FPDM fail, but then again, my F150's I've owned have never seen salt, snow, or off roading conditions that allow this module's backside to corrode.
However, do our engines have two temp controls (a sender and a sensor)? One for the gauge, and one for the PCM/ECU?
I've yet to have an FPDM fail, but then again, my F150's I've owned have never seen salt, snow, or off roading conditions that allow this module's backside to corrode.
However, do our engines have two temp controls (a sender and a sensor)? One for the gauge, and one for the PCM/ECU?
Last edited by Mod (Ret.); 05-08-2015 at 10:08 AM.
05-09-2015, 04:44 PM
#7
Eventually, the engine should stumble and stall. That sensor is used to inform the PCM/ECU that pressure at the fuel rails is there, which in turn is used to inform the FPRM (fuel pressure regulator module; the one by the spare tire that has been known to fail due to corrosion) to turn on/off the fuel pump in the fuel tank.
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05-09-2015, 04:46 PM
#8
05-09-2015, 04:52 PM
#9
The warmed engine "immediate start" or "takes longer to start" has me thinking that the PCM/ECU is not getting the correct engine temp reading. On a detected cold engine, the fuel to air mixture is set higher (fuel) to get a cold engine to start, simular to the days of a choke; the choke would cut off air, and allow the fuel mix to be greater.
Once the engine reaches a certain temp, the fuel mixture is lowered, allowing the engine to return to a normal set idle.
Usually an engine today has two temp devices: a temperature sender, used by the cluster temp guage, and a temperature sensor, used by the PCM/ECU to aid in the adjustment of the fuel to air mapping.
My Ford Ranger had this setup, but not sure if these 4.2/4.6/5.4 engines have two temp devices. Perhaps someone else can chime in.
Once the engine reaches a certain temp, the fuel mixture is lowered, allowing the engine to return to a normal set idle.
Usually an engine today has two temp devices: a temperature sender, used by the cluster temp guage, and a temperature sensor, used by the PCM/ECU to aid in the adjustment of the fuel to air mapping.
My Ford Ranger had this setup, but not sure if these 4.2/4.6/5.4 engines have two temp devices. Perhaps someone else can chime in.
05-09-2015, 04:54 PM
#10