D40 STX fuel pump coming on when engine off
- Thread starter Mccnath
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GAD
Member
I have been chasing this noise since new on a 2010 king cab diesel . Have told Nissan , no help . Lost a fuel cap once , replaced it with a new one and even when the cap was off it still made this noise . On some nights sitting out on the back porch I hear it go off 7 or 8 times never seem to be able , other times once or twice . Can't find this noise and it does p_ss me off .
I've done a little more thinking on this.
The noise simply can't be the fuel pump because that's driven by a chain off the crankshaft. There's no lift pump in the tank either - so we need to look elsewhere.
External electric motors that MIGHT be heard from outside the car:
* External cabin air intake door motors
* Transfer case servo motors
* Headlight adjustment motors
* Wiper washer pump
There might be a motor in the ABS unit.
Now, with those listed (and that might be incomplete), the ONLY one that I can think of that might activate on its own is the external cabin air intake. I have heard my interior doors being moved long after the ignition is turned off - maybe the BCM also does stuff with the external door too.
As to WHY it does it? I don't know.
The noise simply can't be the fuel pump because that's driven by a chain off the crankshaft. There's no lift pump in the tank either - so we need to look elsewhere.
External electric motors that MIGHT be heard from outside the car:
* External cabin air intake door motors
* Transfer case servo motors
* Headlight adjustment motors
* Wiper washer pump
There might be a motor in the ABS unit.
Now, with those listed (and that might be incomplete), the ONLY one that I can think of that might activate on its own is the external cabin air intake. I have heard my interior doors being moved long after the ignition is turned off - maybe the BCM also does stuff with the external door too.
As to WHY it does it? I don't know.
ericcs
Member
had a d21 petrol, now a d40 diesel, and both did/do it. the petrol model did it more, but both get the neighbours looking out the window. definately a random purging/venting thing(with mine anyway)
LLadnar
Member
Both my D40's have made this like electric motor noise thingy after you turn the motor off. It does sound like an electric fuel pump, but I know it's not.
It's strange that it does it across a wide range of models, my first one that did it was a '09 STX and now my new 2012 STX V6TD does it too.
It sounds like it's on the drivers side in the engine bay above the wheel. I know the fuel filter on the 2.5 is in this area but the V9X isn't it think
It's strange that it does it across a wide range of models, my first one that did it was a '09 STX and now my new 2012 STX V6TD does it too.
It sounds like it's on the drivers side in the engine bay above the wheel. I know the fuel filter on the 2.5 is in this area but the V9X isn't it think
So what's in that area? ECM. Wiper washer. IPDM/ER. Brake booster, master cylinder, glow relay. You certainly don't expect any of those items would make that sort of noise.
LLadnar
Member
yeah it's just like a little buzzing noise, I've never really worried about it.
Now I'm wondering.
Now I'm wondering.
Here's an interesting question. Do you have electronic rust protection?
camo.b
Member
Same here.if I shake the truck when off it does it too...
Wait a second. What if it's the fuel tank breather?
When the engine is running, fuel is pumped at ultra-high pressure into the fuel rail, passes through a fuel cooler (in 4WD models) and into the tank. The fuel in the tank is heated by this process.
What if this buzzing sound is air being sucked INTO the fuel tank through a breather, as the fuel's volume is reduced as it cools?
It could do this at any time with ambient temp variations as well. Where's the breather end?
When the engine is running, fuel is pumped at ultra-high pressure into the fuel rail, passes through a fuel cooler (in 4WD models) and into the tank. The fuel in the tank is heated by this process.
What if this buzzing sound is air being sucked INTO the fuel tank through a breather, as the fuel's volume is reduced as it cools?
It could do this at any time with ambient temp variations as well. Where's the breather end?
I am experiencing the fuel pump noise as well. I have a 2010 Navara ST D40 diesel auto. Ever since I purchased it I have noticed this noise. It happens when the vehicle is just sitting there with ignition off and locked up. It also does it when doors closed or vehicle is rocked. Mine is garaged and I have walked past it after a few hours since parking up and heard the noise. It sounds like it is coming from the fuel tank. I have a tradies canopy attached and originally thought that one of my cordless battery drills was running inside canopy because they make a very similar noise. Checked this several times but was not them. Nissan service centre tells me this is normal pump priming noise. If tank does not have pump there must be another motor in the vicinity. It is at the Nissan dealers at the moment having some warranty repairs (diff just repaired in January but making pinging noise now but that's another story) Car does not have a problem with fuel and normally runs well just concerned about whether it is normal as service centre guys say it is.
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It's not a pump priming sound. D40 diesels have a mechanical pump driven by the timing chain on the front of the motor (there's no way an electric motor is going to provide 30,000psi of fuel rail pressure). This is why we still have a primer bulb. There's no pump to lift fuel from the tank, and if there was it'd have to be a high volume pump because when the engine's running and the main pump is hauling arse, the flow rate is extremely high.
Just as a comparison, a Holden Commodore runs its fuel rail at about 45-50psi. Our diesels run typically around 25,000psi for a heavy haul but can reach 30,000 with a full-throttle climb up a hill, turbo at 20psi, engine coolant temps climbing over 100C with ease. At idle, our rail pressures sit at around 4400-4500psi.
As for the noise, I'm stuffed. I don't have directional hearing so I could walk past my car and think the letterbox made that sound.
Just as a comparison, a Holden Commodore runs its fuel rail at about 45-50psi. Our diesels run typically around 25,000psi for a heavy haul but can reach 30,000 with a full-throttle climb up a hill, turbo at 20psi, engine coolant temps climbing over 100C with ease. At idle, our rail pressures sit at around 4400-4500psi.
As for the noise, I'm stuffed. I don't have directional hearing so I could walk past my car and think the letterbox made that sound.
Dave kirkland yorkshire
Member
hi all I have this same issue of the noise of a motor running for 10 seconds or so, I too thought it was the fuel pump until I read this,did anyone get to the bottom of what it is, I’m just curious more than anything
Have a close listen under your dash. The internal doors in my air conditioning ducting are active shortly after I've shut down the car.
Dave kirkland yorkshire
Member
Okay I will have a listen under the dash and report back thankyou for taking the time to reply
