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Low Power + Low Fuel Pressure 2016 Ford Mustang GT
Hey Paul & other Members,
I'm the owner of a 2016 Ford Mustang GT in Australia
Over the past 1.5yrs I've experienced low power problems on my mustang. No DTCs registered
To combat the problem I've along with multiple mechanics have replaced spark plugs, MAF sensor, throttle body, intake manifold, purge valve solenoid, injectors, o2 sensors, catalytic converters, car battery trying to figure out if any of those things were the cause.
I even upgraded my alternator thinking it was a voltage regulator problem since at one point the voltage was jumping all over the place...still no fix to power problem however voltage is more stable now
I connected a BAP (boost-a-pump) module to my fuel pump and that made no difference
Finally I replaced my fuel pump with a new stock fuel pump (which also houses the fuel regulator and fuel filter - its all within one complete unit) and for 1day the car seemed to pick up power again but was very short lived.
After that day, the car was back down on power like it had been for ages.
Out of interest my mechanic connected a fuel pressure gauge and we noticed that the fuel pressure was much lower than factory specs, starting high 50s but slowly dropped till it was sitting at idle around 40psi instead of expected 56-60psi. When we did a WOT pull on the dyno, we saw the fuel pressure drop down as low as 20psi. The power output was also down from expected 400hp to 350hp
I swapped out my fuel pump with my mates stock pump from his mustang (noting that his mustang fuel pressure was 56-60psi) and same story, low on fuel pressure again when connected to my car.
I went to Ford and got them to reflash the PCM back to factory settings, didn't make any difference.
This has really been a huge struggle for me. Dealerships are not interested to help out since car is out of warranty and my mechanics are not sure what is going on. I was hoping someone here would be able to point me in the right direction.
The fuel system is completely stock. Its a dead head system NOT a return style system. Stock fuel pump, fuel lines, fuel injectors, fuel rail. We inspected the fuel hoses/lines, nothing seemed out of order.
I really love this car but I don't want to keep throwing money at it aimlessly hoping to fix the problem. Maybe the low fuel pressure is the main problem, or maybe its part of another issue. We are just not sure.
Hope you can give us some advice.
Cheers
James
Which engine is in your GT? Hoping it's one of the same engines offered here in the US. :silly:
What kind of scan tools do you have available, if any? Because that's the best place to start. The vast majority of Ford products in the last 15 years have used their Fuel Pump Driver Module system. It's an independent module, separate from the PCM, that controls the power and ground to the pump. As you noted, it's returnless, so there's also a fuel pressure sensor.
The PCM will have data PIDs for fuel pressure, desired fuel pressure, FPDM command and feedback. It'll also have fuel trim data which will help confirm a lack of fuel problem. If you don't have a scanner, FORScan is an excellent option.
Its the exact same engine as the 5.0L used in 2015-2017 Mustang GTs
My mechanic used Snap On scanner which is a very expensive tool for diagnosing issues and nothing stood out of the ordinary, the logs looked perfect
I forgot to mention, apart from swapping fuel pump assembly with my mates car, we also swapped the fuel pump driver modules with eachother to see if that made any difference. It didn't help any.
I don't suppose your mechanic kept those data files? I'd be happy to take a look if so.
Even though he looked at it, I still feel that having another look would be beneficial. Especially during a test drive. Watching the PCMs reaction to the low pressure can tell us a lot.
If you've swapped FPDMs and pumps, then my next thought is a voltage drop to the FPDM or the pump. Where does the FPDM live on this Mustang?
It doesn’t have a serviceable fuel filter?? Tank clean from debris just to rule out vandalism?? If that’s good I’d definitely check the power and ground wires.
What other modifications, if any, have been done to the car?
It might be worth it to just pick up at least a cheap scantool that shows live data or better yet the one Tyler mentioned. You said your mechanic didn't see anything unusual but it's hard to tell what people's knowledge is when it comes to this stuff, so sharing some of that info on here could really help you out.
It has a whipple supercharger with a boost a pump and higher flow injectors.
Yes i dataloged the car under wot and see short trim fuel leaning out 10-12%. Tuner thought it may be the boost a pump but thst was good. Noe he thinks it may be my fuel pump going bad.
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