[S550 Question] Hard Start After Refueling (2017 2.3 EcoBoost) - Codes P1450 & P0456 - Purge Valve Replaced

[CoolMonkey]

Hi everyone,

First off, apologies for dropping an S550 question in the S650 section! I have my own S650, but I'm trying to help out a good friend who is having a really frustrating issue with her 2017 and is running out of ideas. I figured some of you might have dealt with this on your previous cars before upgrading, so any insight would be hugely appreciated.

Vehicle: 2017 Ford Mustang 2.3 EcoBoost (US Spec) Error Codes: P1450 & P0456

The Symptoms: Every single time she fills up the gas tank, the first start is extremely rough. It has a hard time starting, sputters, and stumbles. She literally has to pump the gas pedal to get it going.

What we've already done/tried:

• Purge Valve: Replaced the EVAP purge valve/vapor tube assembly (Part # FR3Z-9G297-H).
• Fuel System Flush: We flushed the fuel system. After this, it started perfectly fine a few times, but then the hard start issue came right back.
• Fuel Pump: The fuel pump started making a grinding/clicking noise recently, so that was pulled and refurbished.
• Charcoal Canister: The mechanics suggested swapping out the EVAP charcoal canister (Part # JR3C-9E857-B) hoping it would solve the post-refueling issue. Unfortunately, it didn't help.
• Pressure / Leak Test: The system was fully inspected and pressure-tested. They found zero leaks anywhere. Interestingly, right after the pressure test, the car started beautifully after one fill-up, but went right back to the hard start on the second fill-up.
• Software Bypass Test: As a test, the mechanics temporarily reprogrammed the PCM to ignore the EVAP system so it wouldn't throw codes. Even with the codes bypassed, the car still had the exact same hard start after refueling. They flashed it back to the factory stock tune afterward.

It seems like we've chased down the usual EVAP suspects (purge valve, canister, vacuum leaks), but the issue is completely stubborn.

Has anyone dealt with this after already replacing the purge valve and canister? What else could be causing this vapor lock or flooding situation only after getting gas?

Thanks in advance for the help!

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[Zig]

Any update to airfilter?

 

[Zig]

By chance have you tried: “The "Under-Fill" Test: On your next trip to the gas station, only fill the tank to half-full (1/2 tank). Do not fill it until the pump clicks. If the car starts perfectly at half-tank but stalls at a full tank, it proves that liquid fuel is physically splashing into the vapor lines because the tank's internal float valve is mechanically compromised.”

 

[DarkHorsePremium]

"Only after getting gas"

So once the car is started, it runs normally, accelerates normally, etc?

What about a faulty fuel pressure sensor?

 

[AZ_Ryan]

The 6G forum will be able to help you better.

https://www.mustang6g.com/

 

[tastetickles]

Try what Zig suggested and take note whether after a full tank until click, does the car idle funny like the engine will almost stall out but the ecu stops it by revving high and its rhythmic when this happens almost stall and rev every second during idling.

 

[CoolMonkey]

Thanks for the suggestions! I passed these along to her and here is where things stand:

• Air Filter: She replaces the air filter regularly with every oil change, so that should be good to go.
• The "Under-Fill" Test: She has actually tried this, and unfortunately, it doesn't matter how much gas she puts in. Even if she only fills it up partially, the first start right after adding fuel is always rough.
• The Float Valve: We haven't specifically looked at the internal float valve/sensor yet. It was brought up as a last-resort idea, but her mechanic mentioned that checking or replacing that internal tank valve isn't exactly a simple job.

One very important detail to add: The only times the car has ever started up normally after refueling were directly after the fuel system was flushed, or right after the shop did the pressure test.

Does the fact that it temporarily gets better after a pressure test or system flush point toward anything specific regarding the EVAP lines or valves?

 

[Skye]

Nincs konkrét válaszom. Hivatkozom néhány 6G-s fórumtémára, és mellékelek egy hibaelhárítási útmutatót a hibakódokhoz. Ezekben olyan ötleteket is találhatsz, amelyeket eddig még nem próbáltál ki.

Akár fel is élesztheted az egyik meglévő 6G-s témát, vagy nyithatsz egy újat is. A 6G-n ugyanazzal a felhasználónévvel és jelszóval hozhatsz létre fiókot, mint amit itt használsz. Ha sikerül előrelépned az ügyben vagy megoldanod a problémát, később törölheted is azt a fiókot.

Sok sikert!

I do not have an answer. I'm referencing several 6G threads and attaching a code t-shooting guide. The guide and threads might have some ideas you've not tried before.

You could also bump one of the 6G threads, or start a new one there. You can open a 6G account, using the same username and password as you do here. If you get traction or resolve the issue, you can later delete that account.

Good Luck.

https://www.google.com/search?q=mus...HbBUJVAQrQIoAnoECCAQAw&biw=1460&bih=740&dpr=2

 

[Zig]

By chance has she tried a gas cap test. As in cheap, universal capless fuel tank plug or a locking gas cap designed for Fords. Or try the manual filler neck cleaning trick.

using the white plastic funnel located in the trunk (next to the spare tire/jack):

1. Immediately after pulling the fuel nozzle out, insert the plastic funnel into the neck.
2. Pour a small amount of WD-40 or electronic cleaner directly into the neck around the funnel.
3. Push the funnel in and out rapidly 15 to 20 times.

This may clear out hidden road grit or debris that keeps the spring flaps from snapping shut quickly enough after refuel.

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