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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 48690
Experience:  16 years experience
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2013 6.2 Raptor power drops at around 4-4500 rpm when

Customer Question

2013 6.2 Raptor power drops at around 4-4500 rpm when accelerating and hangs in gear at wot. Graph on tuner shows "line pressure" drops off by 1/3 at the same time. I am not sure but thinking this is fuel line pressure. Pressure is around 900 kPa and drops to 660.
Submitted: 1 month ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 1 month ago.

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Graph on tuner shows "line pressure" drops off by 1/3 at the same time. I am not sure but thinking this is fuel line pressure. Are you saying you do not know if you are monitoring fuel pressure on your graph?

When it hangs in gear is this in all gears or just the higher gears?

Customer: replied 1 month ago.
It happens when trying to pass at Highway speed or when downshifting to go up a hill while towing. It will drop to 3rd and rpms will go to around 4000 and then forward speed stops increasing and rpms rise real slow. It happens on acceleration as well from stop. It will hang in the lower gear until rpm eventually makes it to around 5k or throttle is let up.
The sensor is labeled line pressure. Up to 4k it reads roughly 135 psi and suddenly it drops to around 69.
Expert:  Chris (aka- Moose) replied 1 month ago.

Key in engine off that reading your monitoring does it register a pressure that way?

If you are not running it at hard throttle just normal driving, does it shift right and not have a power loss?

Current miles and at what mileage did this begin?

Customer: replied 1 month ago.
At idle it reads about 69 I believe. Not sure about when the engine is off. It does seem to shift fine when driving around normally or taking off slow. Power is strong til it isn't. If I manually shift it before it reaches 4k it will shift fine but is sluggish because it falls back to a low rpm where power isn't ideal.
It started a couple days ago, mileage is right around 158k.
Expert:  Chris (aka- Moose) replied 1 month ago.

Can you check that pressure reading with the key on engine off so I can see if its transmission line pressure or fuel pressure you are monitoring. It looks like transmission line pressure and if that is the case we need to monitor the fuel pressure.

Customer: replied 1 month ago.
Key on engine off is 69.9 psi.
Expert:  Chris (aka- Moose) replied 1 month ago.

Thanks, ***** ***** were reading it as kpa and now psi, is that correct?

Customer: replied 1 month ago.
It reads out as psi on the tuner. But when I pull up the graph numbers are in kpa.
Expert:  Chris (aka- Moose) replied 1 month ago.

Thanks, ***** ***** engine off there is no transmission line pressure since the engine is not running. So this reading has to be fuel pressure you are monitoring. Engine running fuel pressure should be 350-430 kPa (51-62 psi)

So first off there is something wrong with your reading because your pressure readings are to high. Excessive fuel pressure would be to blame on a faulty fuel pump driver module or fuel pressure sensor.

High fuel pressure though should not cause less power unless it is badly affecting the air fuel ratio.

My suggestion is to try a manual fuel pressure reading with a gauge inline to the injector rail to see if your electronic readings match. If so then I would replace the pressure sensor first off.

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Customer: replied 1 month ago.
Ok. I've been suspecting the driver myself. I'm going to bed for the night but I will check further tomorrow and get back with you.
Expert:  Chris (aka- Moose) replied 1 month ago.

Super

Customer: replied 1 month ago.
Where is the sensor located. On the 6.2 there is no fitting or sensor output. I am unable to find one from aftermarket parts source or dealer.
Expert:  Chris (aka- Moose) replied 1 month ago.

There is not a fuel pressure test port, you have to fabricate an inline T fitting where the fuel line connects to the fuel rail. The fuel pump driver module controls the fuel pressure.

Customer: replied 1 month ago.
I understand there is no test port. Ford has a tool to adapt for a test gauge. What I'm asking is where is the pressure sensor that the ecm reads pressure from in order to control the driver unit.
Expert:  Chris (aka- Moose) replied 1 month ago.

This model shows to not have nor use a pressure sensor. The pressure is regulated by the fuel pump.

Customer: replied 1 month ago.
Then what is sending signal to the ecm that shows line pressure?
And what purpose does the driver relay serve if there is nothing to control it?
Expert:  Chris (aka- Moose) replied 1 month ago.

I thought the same exact things. I assumed there was a pressure sensor on this year like prior years and other liter engines, though there is not. There is not one on the rail for the injectors nor on the fuel line to them. It simply states the pressure is controlled by the fuel pump. So that means the reading you have been monitoring as line pressure is for the transmission and not the fuel system.

Customer: replied 1 month ago.
Ok. Then I don't know why it would show pressure with engine off.
That also means that this problem may have nothing to do with the fuel system.
Expert:  Chris (aka- Moose) replied 1 month ago.

Your weird readings may be coming from a conflict with your scan tool or programmer not correctly communicating with the PCM.

Customer: replied 1 month ago.
Replaced fuel pump assembly today and still having same problem.
Expert:  Chris (aka- Moose) replied 1 month ago.

I am going to throw in the towel on this one. Opting out so another can try.

Customer: replied 1 month ago.
OK. Thanks anyway.
It would seem that load suddenly drops and power is derated. I'm not sure how the load is calculated but could be an issue. I also notice that voltage seems to drop slightly near the rpm where derating happens but never drops below 13.5 volts. I did notice the led light bar was flickering a few nights ago while engine was running but hasn't since. Could a failing alternator cause an issue?