Fuel Cap Warning Light - Ford Truck Enthusiasts Forums



1999 to 2016 Super Duty 1999 to 2016 Ford F250, F350, F450 and F550 Super Duty with diesel V8 and gas V8 and V10 engines SPONSORED BY:
Advertisement

     
Old 11-19-2014, 02:16 PM
How-Tos on this Topic
 
Last edit by: IB Advertising
See related guides and technical advice from our community experts:
  • Warning Lights
    Important information to help you understand your Ford truck

Browse all: Brake Guides
Print Wikipost

Fuel Cap Warning Light

Reply
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 05-18-2012, 07:20 PM
tmaglin's Avatar
tmaglin tmaglin is offline
Freshman User
Thread Starter
 
Join Date: May 2012
Posts: 32
tmaglin is starting off with a positive reputation.
Fuel Cap Warning Light

The fuel cap warning symbol came on in my 2008 super duty with 5.4 gas engine. I removed and reinstalled the cap, symbol still on. Replaced the cap, symbol still on. Any ideas on what's cauaing this to stay on? Thanks in advance. I appreciate all help.
Reply With Quote
  #2  
Old 05-18-2012, 10:49 PM
Quad Racer's Avatar
Quad Racer Quad Racer is offline
Posting Guru
 
Join Date: Jun 2011
Location: Cincy
Posts: 1,897
Quad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to all
I just had this the other day. I recently installed a locking gas cap and things were fine for a couple weeks. Gassed up one day and had the light on. Once I checked, I noticed the cap was slightly cross threaded. It seems like the locking gas cap's threads fit on the loose side. Havent had an issue from it since.
Reply With Quote
  #3  
Old 05-19-2012, 06:23 AM
RPM371's Avatar
RPM371 RPM371 is offline
Senior User
 
Join Date: Apr 2012
Location: Texas
Posts: 340
RPM371 is gaining momentum as a positive member of FTE.RPM371 is gaining momentum as a positive member of FTE.
It may need a new cap. They are cheap to replace.
Reply With Quote
  #4  
Old 05-19-2012, 07:01 AM
tmaglin's Avatar
tmaglin tmaglin is offline
Freshman User
Thread Starter
 
Join Date: May 2012
Posts: 32
tmaglin is starting off with a positive reputation.
Quote:
Originally Posted by RPM371 View Post
It may need a new cap. They are cheap to replace.
Did that, but it didn't help.
Reply With Quote
  #5  
Old 05-19-2012, 08:12 AM
tmaglin's Avatar
tmaglin tmaglin is offline
Freshman User
Thread Starter
 
Join Date: May 2012
Posts: 32
tmaglin is starting off with a positive reputation.
If I remember correctly, I was driving and hit a pothole in the road, then instantly the warning symbol came on. Does anyone know how this system works? Is there a sensor on the tank or is this controlled by the computer?
Reply With Quote
  #6  
Old 05-19-2012, 08:40 AM
senix's Avatar
senix senix is offline
Moderator
 
Join Date: Aug 2008
Location: Frederick, MD
Posts: 26,465
senix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputationsenix has a superb reputation
it is a closed system so you have an issue somewhere. I'd suggest looking at the fuel lines going from the cap to the tank and the evap cannister.
Reply With Quote
  #7  
Old 05-19-2012, 09:05 AM
brd7666's Avatar
brd7666 brd7666 is offline
Elder User
 
Join Date: Jul 2010
Location: Clearwater Fl.
Posts: 983
brd7666 has a very good reputation on FTE.brd7666 has a very good reputation on FTE.brd7666 has a very good reputation on FTE.
Try disconnecting the battery cable from the battery. Sometimes they need to be reset, and disconnecting the battery will do that. Try it and see what happens. Good luck.
Reply With Quote
  #8  
Old 05-19-2012, 09:23 AM
tmaglin's Avatar
tmaglin tmaglin is offline
Freshman User
Thread Starter
 
Join Date: May 2012
Posts: 32
tmaglin is starting off with a positive reputation.
Quote:
Originally Posted by brd7666 View Post
Try disconnecting the battery cable from the battery. Sometimes they need to be reset, and disconnecting the battery will do that. Try it and see what happens. Good luck.
Thanks brd7666. That worked.
Reply With Quote
  #9  
Old 05-19-2012, 09:33 AM
Quad Racer's Avatar
Quad Racer Quad Racer is offline
Posting Guru
 
Join Date: Jun 2011
Location: Cincy
Posts: 1,897
Quad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to allQuad Racer is a name known to all
Glad it was a simple fix. Most often it is.
Reply With Quote
  #10  
Old 05-19-2012, 09:41 AM
projectSHO89 projectSHO89 is offline
Post Fiend
 
Join Date: Jan 2004
Location: St Louis
Posts: 12,048
projectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant futureprojectSHO89 has a brilliant future
Condensed version of how it works:

The EVAP system is supposed to prevent fuel vapors from escaping into the atmosphere. The fuel tank is vented through a carbon canister via the canister vent solenoid which is controlled by the PCM's programming. During normal driving, the vent is open allowing air into (or out of) the fuel tank through the canister.

Since the vapor system is supposed to be closed for the fuel vapors, it must be tested periodically. The PCM does this by closing the vent solenoid, opening the purge valve to apply manifold vacuum to the system, them measuring the air pressure (vaccuum) inside the tank using the fuel tank pressure sensor located in the top of the fuel tank. A properly sealed system will bleed up vacuum within a certain amount of time. The system the shuts the purge solenoid and measures bleed-down time to verify system is sealed. Leaks can be identified by the rate of bleed down and classified as large or small.

After fueling, as detected by the fuel level sender in the tank, the system runs a "mini-check to verify it can draw a vacuum on the tank. If the system cannot draw a vacuum, it concludes that the fuel cap is probably not sealed and lights the fuel cap warning light.

Now, to your specific instance:

1) Next time, don't futz with the battery. Just pull the PCM KAM fuse if you want to reset the PCM's memory. That way, you don't have to reprogram the radio!

2) Resetting the computer as you did makes it so the fuel cap "mini-check" wasn't run since it only runs after you fill up the tank. You just turned off the light, but the underlying problem may (and very likely still does) exist. You'll find out the next time you refuel. Don't be too surprised if you happen to get a MIL with an evaporative emissions leak DTC in the meantime. If it does, you're going to need advice or assistance from someone who knows what they're doing or talking about...
Reply With Quote
  #11  
Old 05-19-2012, 10:58 AM
tmaglin's Avatar
tmaglin tmaglin is offline
Freshman User
Thread Starter
 
Join Date: May 2012
Posts: 32
tmaglin is starting off with a positive reputation.
Thanks for the info. I'll find out what happens as I'll be fueling later today. I appreciate your knowledge on system ops.
Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
2005 6.0 crank no start rstpe 6.0L Power Stroke Diesel 24 03-02-2016 08:05 PM
Fuel Cap warning light. Bruker General Automotive Discussion 5 07-03-2012 04:33 PM
Gettin ready to throw in the towel HELP 5Rangers 1987 - 1996 F150 & Larger F-Series Trucks 4 07-25-2011 10:42 PM
Engine Symbol (Service engine soon) on Dash Forest Excursion - King of SUVs 14 02-13-2011 09:46 PM
emissions symbol on dash scrooge 2004 - 2008 F150 7 03-01-2005 03:42 PM


Go Back   Ford Truck Enthusiasts Forums >

Tags
2004, 2008, cap, coming, edge, f150, f250, ford, fuel, gas, light, loose, ranger, reset, tsb, warning

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump


All times are GMT -5. The time now is 04:54 AM.


This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company.