2016 Mustang V6 will crank but not start

Cajunhunter67

New Member
May 18, 2020
2
0
1
53
Louisiana
Hi all!
This is a car I purchased for my daughter.
It does this after it has sat for a bit. If you crank right after shutting it off, the car will crank up and run.
Otherwise, You push the brake, hit the start button, and it will just turn over and never fire up. If I hit the Start/stop button, and then try again it will usually run after the third try.

I intend to have the dealer check it out, but we all know how intermittent issues get resolved....they don't.
It is starting to happen often. Almost every time, so there is a possibility it will do it for the dealer.
She is only 16 yrs old, so I don't want her broke down anywhere.
Hoping someone has experienced this issue and can give me an idea how to fix it.

Don
 
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MustangIIMatt

Easy there, this ain't a dating site.
15 Year Member
Mar 7, 2002
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This is almost certainly a failure in the fuel pump or fuel pressure regulator.

Both are mounted in the fuel tank, what I don't know, as I haven't taken the tank down on an S550 (or opened the access panel if it has one) is whether they're separate or sold as a unit.

I see and/or fix similar issues somewhat frequently on the BMWs I work on for a living, and have seen it on other makes as well when working at other dealerships.

There are other possibilities, but all a tech would need to do to either diagnose it or get started down the right path is let it sit overnight and then press the start button without pressing the brake while the scan tool is hooked up. If it isn't still primed from the previous start, the system is bleeding down excessively. If it doesn't build the correct amount of pressure on the first try, and takes a few to do so, either the fuel pump is weak, the fuel strainer is clogged, a hose or tube inside the tank has split, or the fuel pressure regulator has failed.

Ford more than likely has a test that will let said technician figure it out if he knows what he's doing.

Being an Ecoboost, there is also the possiblity of the high-pressure fuel pump mounted to the valve cover having failed, but that will usually turn on the check engine light if there's a sensor attached to it (the HPFP failing can cause the air/fuel ratio to lean out and damage the engine, so most manufacturers monitor it directly).
 
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Cajunhunter67

New Member
May 18, 2020
2
0
1
53
Louisiana
Thanks for the reply
Thats a huge help as it's what I thought it might be. I wasn't sure if the system had a check valve that was failing. But it definitely seems to be fuel pressure or fuel pump related. I'm not familiar with this system.
I believe you hit the nail on the head. They could let it sit for only an hour or over night. Put the laptop on it and see if the required fuel pressure is available.

I will try and get the car to the dealer this week. Will update with findings.
Thank you for the quick response.

Don