[alpha2turbo]

So in the last month I've had 3 instances when starting my car it stumbles for a few minutes and wants to die. It definitely feels fuel related. It has been completely random and after a few minutes it drives fine. When I watch my HPFP pressure on my AP it is all over the place during that time. Once it settles down it drives fine, pressure looks fine, afrs look fine and it pulls normal up to redline. This is what is confusing me. I can start it the very next time after driving it with the issue and it starts and idles fine. It happened twice in 1 week then went away for a few weeks until last night again. What do you guys think it could be?

2014 Focus ST with Cobb AP stage 3 ots map with supporting mods.

 

[Freebird23103]

Sounds like the hpfp may be giving up soon thus the fluctuating fuel pressure. If it is going out I would think it would get worse with time.

 

[tpiechow]

Well the kicker is, you can't condemn the high pressure fuel pump until you verify the low pressure fuel pump. If the low pressure fuel pump is not giving enough supply or pressure, the high pressure pump is useless.

There is a sensor called the FLP (fuel line pressure) which monitors the low side pressure. I don't know if the AP has an option to monitor it, but if it does I would monitor it while the concern is present. If the low side is steady and the high side is erratic, then its the high pressure fuel pump. And if both the high pressure and low pressure are erratic, most likely it is the low pressure pump in the tank.

Keep in mind that these engines can idle and handle light load throttle with like 50 PSI. So you can unplug the FVR (fuel volume regulator) on the HPFP and the engine will still run. Unplugging the FVR will stop the HPFP from building pressure and you would have the same pressure at the injectors as you do the low pressure side. Mess with the low pressure pump and that is when you start to notice drive-ability concerns.

 

[FoST2016]

It does sound like a pump issue. I'm curious though, have you been monitoring AFR? Has it been steady? Also, what is your LTFT at idle?

 

[Burnboy]

Do you top off your tank when filling up? Meaning after the pump clicks off do you top it off after that? Or does this happen after filling the tank?

 

[JoshCrane1]

Mine does this only on fillups, every single time just about I gotta blip the throttle cause it wants to die after filling up. Second crank and fires up
if it does die.

Now i just fill up with the engine running, problem solved, no other issues. Almost like there's a bubble in the tank and venting to fill up does something.

 

[cardwzzle]

Mine does this only on fillups, every single time just about I gotta blip the throttle cause it wants to die after filling up. Second crank and fires up
if it does die.

Now i just fill up with the engine running, problem solved, no other issues. Almost like there's a bubble in the tank and venting to fill up does something.

Problem solved!

Sent from my SM-G900T using Tapatalk

 

[JoshCrane1]

Problem solved!

Sent from my SM-G900T using Tapatalk

Not worried, myth busted. lol

 

[alpha2turbo]

It does sound like a pump issue. I'm curious though, have you been monitoring AFR? Has it been steady? Also, what is your LTFT at idle?

When it happened last time AFR was all over the place. When it settles down and I do some light pulls I can do a full throttle pull and it holds steady. I have even done multiple WOT pulls back to back and everything looks normal. That's what confuses me. If it was a pump issue I would assume it would be constant.

 

[alpha2turbo]

Do you top off your tank when filling up? Meaning after the pump clicks off do you top it off after that? Or does this happen after filling the tank?

Not more than a few cents to make it even, 5-10 cents not like $1 or anything. It happened when I had about 1/4 tank the first time so I thought it was maybe something in the tank. The next time it was like half tank and the other day it was also about half a tank.

 

[Burnboy]

Mine does this only on fillups, every single time just about I gotta blip the throttle cause it wants to die after filling up. Second crank and fires up
if it does die.

Now i just fill up with the engine running, problem solved, no other issues. Almost like there's a bubble in the tank and venting to fill up does something.

I bet you're getting raw fuel into your vapor recovery system and into the charcoal canister. You need to take it in.

 

[Burnboy]

Not more than a few cents to make it even, 5-10 cents not like $1 or anything. It happened when I had about 1/4 tank the first time so I thought it was maybe something in the tank. The next time it was like half tank and the other day it was also about half a tank.

I'm wondering if you have a tank purge valve issue as well maybe getting fuel in the charcoal canister. The 13's have a tsb about this and it can suck the gas tank flat and crush the fuel sending unit. I'd also have it looked at or check your tank yourself and reference the tsb. I found the tsb on line via google

 

[Burnboy]

Do not ever top off the tank on newer cars

 

[Burnboy]

http://www.focusst.org/forum/attach...ocus-st-model-year-13-present-tsb13-12-04.pdf

 

[PiratesLIFE4ME]

So in the last month I've had 3 instances when starting my car it stumbles for a few minutes and wants to die. It definitely feels fuel related. It has been completely random and after a few minutes it drives fine. When I watch my HPFP pressure on my AP it is all over the place during that time. Once it settles down it drives fine, pressure looks fine, afrs look fine and it pulls normal up to redline. This is what is confusing me. I can start it the very next time after driving it with the issue and it starts and idles fine. It happened twice in 1 week then went away for a few weeks until last night again. What do you guys think it could be?

2014 Focus ST with Cobb AP stage 3 ots map with supporting mods.

Very common issue. I am pretty sure it is your canister. There is a tsb for this and it is covered under warranty.

View attachment tsb13-12-04.pdf

 

[PiratesLIFE4ME]

The guidelines state you must have inaccurate fuel gauge reading or a cel. I had this issue, and I have talked to many other people with similar complaints. It starts off like what you said and slowly escalates until you get the symptoms Ford requires to cover it.

 

[PiratesLIFE4ME]

I bet you're getting raw fuel into your vapor recovery system and into the charcoal canister. You need to take it in.

I'm wondering if you have a tank purge valve issue as well maybe getting fuel in the charcoal canister. The 13's have a tsb about this and it can suck the gas tank flat and crush the fuel sending unit. I'd also have it looked at or check your tank yourself and reference the tsb. I found the tsb on line via google

You beat me to it. Lol. I was googling the tsb.

 

[JoshCrane1]

Would the TSB cover a 14'? My fuel gauge gets wonky as well from time to time.

 

[Burnboy]

It should. But Ford is strange.

 

[alpha2turbo]

Very common issue. I am pretty sure it is your canister. There is a tsb for this and it is covered under warranty.

View attachment 201826

I do occasionally have very erratic miles to empty issues. Sometimes it will drop 30-40 miles almost instantly.