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Check engine light

rdeschenerdeschene Posts: 331
edited January 2016 in Ford
I have a 2012 Ford Fusion SEL. In late December, the check engine light came on (steady, not flashing). I took it to a local mechanic, as the nearest Ford dealership is a 45-minute drive away. He said an evap code came up indicating that there was a problem with the vent valve solenoid, not the capless fuel filler. However, he did not have the diagnostics to research it further.

As there have been problems with the vent valve solenoid, including a recall (for which we do not qualify), my husband bought and installed the part on Jan. 7. We both drove it several times since then, and the check engine light stayed off. But when I drove it today (Jan. 11), the light was back on.

Any suggestions as to what the problem might be? I suspect I will have to drive to the Ford dealership, but I would like to have some idea of the range of problems I might expect before I make that trip.

Thanks!

Comments

  • rdeschenerdeschene Posts: 331
    Actually, it was the purge valve solenoid that my husband replaced. Sorry about that!
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    edited January 2016
    It could be some kind of vacuum leak--loose or split hose in the EVAP system, or a junked-up capless fuel neck.

    You might find THIS VIDEO interesting, especially around the 5.00 mark.

    You should also watch the video on How To Maintain the Capless Fuel Filter
  • rdeschenerdeschene Posts: 331
    Thanks for the video link. My husband had already done some research and watched that video, which prompted him to start out by cleaning the capless fuel filler.

    Update: Interestingly enough, the check engine light went back off last Thursday. However, as I'd already made an appointment at the dealership, I kept it and went today, to at least see what the code(s) said. The code that came up is P0451, indicating an evap system leak. They told me the specific problem is the fuel tank pressure sensor, which will need to be replaced.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Well it could be but a code cannot positively identify the defective part. So unless they actually tested the pressure sensor, the solution is still up for grabs.
  • rdeschenerdeschene Posts: 331
    They said they ran a point-by-point check, and that's what they came up with.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Well let us know how it turns out.
  • rdeschenerdeschene Posts: 331
    Thanks, will do! The odd thing is that the check engine light is not on, and hasn't been since last Thursday. You'd think that would mean there's no problem, but I guess not.
  • thecardoc3thecardoc3 Posts: 5,255
    What it means is that the failure is intermittent. Combine that with the fact that it has to fail two times in a row to turn the light on, and then pass two times in a row to turn the light back off and you can get periods of time when the light can be on or off.

    The testing is pretty straight forward. Key On Engine Off (KOEO) Using a scan tool the tech has to access the fuel tank pressure sensor data and see if it is measuring atmospheric pressure or not. With the engine off and the evaporative test not running the canister and tank should be at atmospheric pressure. If the sensor shows something other than that, then the tech would manually open the filler, or command the purge valve on with the bi-directional controls which should bleed off any trapped vacuum or pressure. If the sensor doesn't show 0"water pressure (2.5v) then the sensor has lost its calibration and needs replaced.
  • rdeschenerdeschene Posts: 331
    Thanks for that clarification, thecardoc3!

    Another question: The fuel economy on our 2012 Fusion SEL has been a little underwhelming. The EPA-rated MPG is 23 city/33 highway, but we've never reached 33. I do a lot of in-town driving, but even on stretches where we do more highway driving, the best we've been able to manage is 29 MPG. We keep our tires properly inflated and do other routine maintenance. Would a small evap leak affect fuel efficiency? I tend to think not, but figured it couldn't hurt to ask.
  • thecardoc3thecardoc3 Posts: 5,255
    edited January 2016
    No, the evaporative system issue would not have any impact on your fuel economy.
  • rdeschenerdeschene Posts: 331
    edited January 2016
    Thanks, that's what I thought. I'm perplexed as to why our fuel economy is not as advertised. We brake well ahead of a red light, don't accelerate quickly when it turns green. I prefer to stay in the same lane whenever possible. I guess you could say I'm a very cautious driver, and I do most of the driving for this vehicle. We also put winter tires on, and I know that reduces fuel efficiency. However, when I say that 29 MPG is our maximum, that's during the summer, and also during mostly highway driving.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    edited January 2016
    To reach the stated 33 mpg you'd have to be doing all highway driving. It's really an optimum number, and even then depends on terrain and vehicle speed and even wind speeds. I bet on a flat highway using cruise control you could do it. I checked at www.fuelly.com and they reported that the average MPG from 107 year 2012 Fusions was 28.6 mpg. Only 3 of the 107 cars that reported in got 33 mpg.

    So statistically at least it seems like your car is okay.

    I also checked the fuelly numbers for my car and I have to say they were right on the money.
  • rdeschenerdeschene Posts: 331
    Ah, OK. We live in an area where there's no such thing as a flat highway. All our highways and roads are near the ocean, with lots of steep hills and curves. That explains it!
  • Sorry to be so late in posting an update. Because of bad weather on my original appointment date, I had to reschedule my appointment for Wednesday. The fuel tank pressure sensor was replaced, and then the mechanic cleared the code and verified the repair. Since then, so far so good. No check engine light!
  • OK, you know how I mentioned fuel economy before, and how underwhelming it is? Today I filled up the Fusion (remember, this is post-repair). I'd done a fair bit of highway driving between the last fill-up and this one, all driving I've done before, and this time the fuel economy was markedly better: 35 mpg. Is there any reason to believe that replacing the fuel tank pressure sensor would cause this to improve?
  • thecardoc3thecardoc3 Posts: 5,255
    No. The sensor is only reporting the vapor pressure inside the fuel tank for the evaporative system and is not used for fuel control at all.
  • I thought so. Hmmm ... trying to figure out why this suddenly "optimistic" fuel economy turned up. My mileage and fill-up figures for both entries are correct, so that's not the problem.
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