2007 1.5dci fuel pressure sensor

Forum for Engine, Exhaust, Drivetrain, ECU
Post Reply
sparks2555
Posts: 7
Joined: Mon Nov 29, 2021 2:04 pm
Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by sparks2555 »

Hi everyone.. im having a problem with my fuel pressure sensor.. on checking the voltage with the sensor unplugged i find the folllowing. gray wire ground 12v between battery positive so the ground is good. Blue i think is 5v reference and tests 5.1v between blue and gray all ok so far .. that leaves just the light green wire ... i would have expected this to read 0v as its not connected to the sensor but it reads 5.1v all the time . i have metered it out to the ecu thinking it must be shorted to 5v but i cant find anything.. the result of this being that the ecu sees 5v on its input instead of a voltage between 0v and 5v and so thinks that the fuel rail pressure is 26000psi and dosent command anymore. Any thoughts ... i suppose i would like to know if i am correct i thinking that the blue wire is the 5v ref and the light green is the sig out.. either way i still have 5v on both :?: :?: :?: :?: :?:

sparks2555
Posts: 7
Joined: Mon Nov 29, 2021 2:04 pm
Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by sparks2555 »

Edit .. just a thought .. is the sensor a pull down type ie the 5v is pulled towards ground as pressure decreases.. if i insert a 5k resistor between gray and green my torque app pressure gauge reads about half ie 13000psi ... Thanks.
lewisbryant
Posts: 336
Joined: Sat Feb 23, 2019 7:27 am
Qashqai Model: Mk.3 Qashqai - J12 (2021+) New Model

Post by lewisbryant »

You should back probe the sensor wire and read the voltage.

Alot of the time signal wires have a bias/diagnostic voltage on them so the 5v supply is given out through a resistor on the signal wire.

Regardless of testing it though what pressure are you getting when cranking you should be getting atleast 300 bar with engine speed 250rpm.

Most common issue on old j10 is the primer bulb has cracked at its joints and causes a no start and fuel pressure issues
sparks2555
Posts: 7
Joined: Mon Nov 29, 2021 2:04 pm
Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by sparks2555 »

Hi thanks for the reply ... ok first symptoms were driving fine but when putting the boot down she would go into limp mode (i think) red engine warning light on and no power .. upon checking torque app it was only giving 2000 to 6000 psi. so sensor change (2nd hand) no difference. switching off the ignition and restarting cleared this for a while but it got worse. now the fuel pressure reads 26000 with the sensor connected or disconnected .. engine will not rev above 2k and red engine warning light permanantly on . i have checked the fuel system for leaks etc all ok
lewisbryant
Posts: 336
Joined: Sat Feb 23, 2019 7:27 am
Qashqai Model: Mk.3 Qashqai - J12 (2021+) New Model

Post by lewisbryant »

So when you unplug it the scan tool reads 26000 psi and the voltage on signal wire is 5v?

And when you pull the signal down to ground with a 5k resistor you get 13000psi ?.

Could you do me a favour and check the voltage on the signal wire when plugged in and check what the ecu is reading at same time with just ignition on. Back probing the signal wire yeah

Then do same test but with it idling ?

This will give me an idea of what the issue is.
sparks2555
Posts: 7
Joined: Mon Nov 29, 2021 2:04 pm
Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by sparks2555 »

would you believe im now getting a no start due to a crankshaft intermittent code.. i may have damaged the ecu side of the plug while probing for the fuel sensor .. iv ordered a crank sensor but it will be wed evening before i get back to it .. ill let you know and thanks again for helping .. Joe
sparks2555
Posts: 7
Joined: Mon Nov 29, 2021 2:04 pm
Qashqai Model: Mk.1 Qashqai - J10 (2006–2013)

Post by sparks2555 »

Hi lewis i hope you see this... sorry for the late update but my job takes me offshore for months at a time. The problem turned out to be the connector, the +5v pin was not making contact with the sensor pin... easy fix . i found this by taking the sensor to the bench and powering it up on a psu at 5v. current draw was 4mA . Back on the car i cut the 5v wire and put a merer in line 0mA so off with the old and in with the new... perfect first time. Thanks for your help... Joe
Post Reply