Dirty fuel tank vacuum sensor?

Rangerguy

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My Ranger threw an engine check light: Power train control system, evaporative emissions system, excess vacuum fuel tank while driving. I took it in for service. They said the FTP (Fuel Tank Pressure) sensor was dirty with undercoating oil, cleaned it off, reset the calibration and cleared the check light (at my expense). They said the sensor is on top of the fuel tank. But I don't get it: is the sensor measuring atmospheric pressure so the system can compare that with air pressure inside the tank? And if it got dirty so it couldn't sense how could that be prevented in future?
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Porpoise Hork

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Sounds like they may have scammed you. For starters depending on the mileage of the truck, this should have been covered under warranty. To add to this, If it's really the fuel tank pressure sensor they "cleaned" they would have had to drop the tank to get to it. That sensor is attached to the fuel sending unit assembly and the sensor sits inside the tank and is not exposed to atmospheric conditions. It has an electrical harness connection to it that is external and that's it. There's nothing to clean on it. The only other thing is the Vapor Canister Purge Solenoid, but it too is not directly exposed to atmospheric conditions. one side connects to the vapor canister and the other to the PCV system.
 

FULLSCALE

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My Ranger threw an engine check light: Power train control system, evaporative emissions system, excess vacuum fuel tank while driving. I took it in for service. They said the sensor was dirty with undercoating oil, cleaned it off, reset the calibration and cleared the check light (at my expense). They said the sensor is on top of the fuel tank. But I don't get it: is the sensor measuring atmospheric pressure so the system can compare that with air pressure inside the tank? And if it got dirty so it couldn't sense how could that be prevented in future?
That‘s exactly right, it measures atmospheric pressure to compare. I had the same codes and the dealer did the same thing, tried to clean but it didn’t fix the problem. They just replaced the tank pressure sensor/line this week and all is well. They did it under warranty and told me to make sure from now on to tell whoever is spraying the truck knows to avoid spraying above the tank or at the very least apply a very light coating.
 
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Rangerguy

Rangerguy

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Story continues. Talked to the undercoat shop. They checked with head office who confirmed that they had issued a direction not to spray in that area above the fuel tank on these trucks. So they gave me credit on next years undercoating. All good until last night: got the same error code check light again. Back to the dealer next week.
 

Radioman

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Story continues. Talked to the undercoat shop. They checked with head office who confirmed that they had issued a direction not to spray in that area above the fuel tank on these trucks. So they gave me credit on next years undercoating. All good until last night: got the same error code check light again. Back to the dealer next week.
Good luck on the issue but it's a nice picture of the dampener. :like:
 


jlarrabee104

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An interesting issue that I'm starting to notice. My truck just popped that code last night on my way home from work. I had mine undercoated last year without issue and again about a month ago. My only concern is even without undercoating the top of the tank gets dirty and that sensor will be junk after 100,000 miles on the Northern Salted Roads.

Called my dealer and will bring it to them Monday...
 
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Rangerguy

Rangerguy

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An interesting issue that I'm starting to notice. My truck just popped that code last night on my way home from work. I had mine undercoated last year without issue and again about a month ago. My only concern is even without undercoating the top of the tank gets dirty and that sensor will be junk after 100,000 miles on the Northern Salted Roads.

Called my dealer and will bring it to them Monday...
I learned that it can take time for undercoating to penetrate and damage the sensor. The dealer had to replace the sensor. Cleaning was not enough.
 

JTDay

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I'm not sure how this happens but there is another thread or post somewhere on here about this same issue. Definitely an odd one.
 
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Rangerguy

Rangerguy

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D Fresh

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When will you people learn to stop spraying oil on your undercarraige?
 

Jason B

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When will you people learn to stop spraying oil on your undercarraige?
Don't worry, they will do better on the fourth year. I bet every time it was sprayed, it was by a different guy that wasn't briefed on the procedure.
 

Jason B

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My '95 F150 with 360K miles had an automatic undercarriage oil system, even though it is not needed in Louisiana.
Odd thing was that you had to add a quart of oil once a month to the engine for it to be effective.
 

IdahoRanger

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My '95 F150 with 360K miles had an automatic undercarriage oil system, even though it is not needed in Louisiana.
Odd thing was that you had to add a quart of oil once a month to the engine for it to be effective.
LOL, my 92 had the same system. Also, it always had clean oil so didn't need changing. :p
 

Racket

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When will you people learn to stop spraying oil on your undercarraige?
It's pride month, don't be so judgemental 🤪
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