Noise when key is inserted in ignition. Not turning the key at all, just inserting the key into the ignition I hear a noise what I believe is coming from the rear. Tough to the describe but sounds like a faint thud thud thud. Could it be the fuel pump priming? brakes applying?
Anyone notice this?

Truck is 2016 SCSB F150

 

The truck "wakes up". Your hearing the fuel pump from the rear.

 

Yep. A lot of them do it as soon as you unlock and open the driver door.

 

Well good to know, thanks for the reply's.

 

I don't believe the 2016 has the early priming feature does it?

I have a Pushbutton start but I'm pretty sure the fuel pump is not active if I push the button for accessory mode, which is even one step further than inserting a key, not turning to accessory.

The 2016 shouldn't have an electronic parking brake yet either? Maybe the 2.7l truck was equipped with electronic parking brake?

I don't think a fuel pump will make repeated thud sounds.

 

Could be Jimmy Hoffa trying to get out.

 

My 16 5.0 XLT primed the pump, lights on, subwoofer thumped and probably more stuff that helped to drain the battery. Although, I don't recall ever using the key to unlock the truck.

 

Truck has electric parking brake. Not sure thud is the best description but does have a noise from the rear when key is inserted. Surprised it primes the pump with out turning key to accessory.

 

By priming the pump it reduces the amount of complaints from owners in regards to the number of evolutions required to start the engine.

I've had a few vehicles over the years that I installed an aftermarket fuel pump, and just got in the habit of a routine of ignition on, fuel pump on, then start. And idle until the oil pressure came up prior to putting the transmission in gear.

My wife on the other hand, waste no time from the moment she walks up to her car and the doors unlock, she is in the drivers seat with car in reverse within seconds of engine start.

 

I feel fortunate to have a Lariat for one of 2 reasons:
1) in 2016 the Lariat push button truck does not prime the pump
2) the 2016 Lariat is so quiet I can't her it prime. I hear the pump, but not until I initiate a start sequence.

The newer models include a drain back valve and those models will prime when the door is open to build pressure from an 'empty' system.
I don't know the earlier models ever lost fuel pressure at the injector. Within reason of course, but not an empty fuel line.

I think the owners manual from years and years ago actually instruct drivers to turn key on and wait a moment for the system to prime.
Having fuel injection since around 1991/1992, I feel safe saying I've never had an extended crank from turning the key as soon as I've inserted key to ignition.
I'm also pretty confident that a battery has been dead before I got tot he vehicle, but never when I tried to start, meaning all the things we say contribute to draining a batter, really doesn't.