'Check Fuel Cap' warning lamp stays on

[Invective]

Started this morning after driving approx. 5 miles. Aftermarket locking cap on as snug as ever. Riding around on teeth jarring washboard roads recently. Any thoughts?

[Ambitious1]

I have had this issue on different cars with aftermarket locking caps. Sometimes you have to just take it off and put it back on again. See if that works.

[martyo]

I think you can use your sct programmer to resent the light. Then see if it returns.

[fastblackmerc]

Probably the cap. Use the original cap unless there is a problem with gas theft in your area.

[Invective]

Reset fuel cap - no change. 'Check Engine' lamp came on this afternoon, followed by periodic 'erratic idle' - no stalls, but close. Left at local repair shop here in SC - reputable and appears to be well equipped. Service Writer - Dispatcher had never heard of a 'Mercury Marauder'(?!?!) but was impressed otherwise. Shop was advised: 'Do NOT reflash ECM'. Know something tomorrow. Won't be home until early next week at the soonest.

[Invective]

Picked up car: Canister Purge Solenoid replaced. Running well again with a steady, semi smooth idle (good). Before the last malfunction, the car would alternate between a 'nervous' idle (lean trim) and the normal 'semi smooth' idle. I'm happy again. :coolman:

[RF Overlord]

OK, I'm asking for a reason...was it the Canister Vent Solenoid or the Canister Purge Valve? (they are 2 different things...one's in the engine compartment and the other's in that tray under the trunk)

[Invective]

OK, I'm asking for a reason...was it the Canister Vent Solenoid or the Canister Purge Valve? (they are 2 different things...one's in the engine compartment and the other's in that tray under the trunk)

From the RO:

Parts: Vapor Canister Purge Valve

Labor: Replace Canister Purge Solenoid

[RF Overlord]

I'm having an EVAP issue with my 2004 Grand Marquis and was hoping they would be more accurate in describing which piece they replaced...oh well.

[Invective]

I'm having an EVAP issue with my 2004 Grand Marquis and was hoping they would be more accurate in describing which piece they replaced...oh well.

Shop is closed weekends. I will contact them monday and report back. Judging by what I was charged, the 'purge valve' was changed out - heck of a markup too. I'll find out for sure monday. Motorcraft device depicted.

https://proxy.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.carid.com% 2Fimages%2Fmotorcraft%2Femissi on-control%2Fcx1810.jpg&f=1

https://www.carid.com/motorcraft/vapor-canister-purge-valve-mpn-cx1810.html?singleid=23874067&url=12770410

[RF Overlord]

Yup, that's the Purge Valve...lives on the firewall, passenger side. Ford officially calls it the Vapor Management Valve, but yeah...that's not the Canister Vent Solenoid.

Thanks for clarifying. :D

[sailsmen]

Subscribing................... .......ds;ofda,kzdfzvnli n c fmjz sru,g

[Invective]

Yup, that's the Purge Valve...lives on the firewall, passenger side. Ford officially calls it the Vapor Management Valve, but yeah...that's not the Canister Vent Solenoid.

Thanks for clarifying. :D

Learned something today. Didn't realize there were two electrical devices involved in venting the fuel fumes on modern cars. Still recall the singluar vacuum operated 'canister purge/vent valve' on early emissions controlled cars.

http://www.allpar.com/photos/fix/fuel/canister-top-purge-valves.jpg

[RF Overlord]

This is from the 2004 OBD System Operation Manual from Ford:

"First, the Canister Vent Solenoid is closed to seal the entire evap system, then the VMV is opened to pull a 8" H2O vacuum. If the initial vacuum could not be achieved, a large system leak is indicated (P0455). This could be caused by a fuel cap that was not installed properly, a large hole, an overfilled fuel tank, disconnected/kinked vapor lines, a Canister Vent Solenoid that is stuck open, a VMV that is stuck closed, or a disconnected/blocked vapor line between the VMV and the FTPT."

P0455 is what I'm getting.

[Invective]

This is from the 2004 OBD System Operation Manual from Ford:

"First, the Canister Vent Solenoid is closed to seal the entire evap system, then the VMV is opened to pull a 8" H2O vacuum. If the initial vacuum could not be achieved, a large system leak is indicated (P0455). This could be caused by a fuel cap that was not installed properly, a large hole, an overfilled fuel tank, disconnected/kinked vapor lines, a Canister Vent Solenoid that is stuck open, a VMV that is stuck closed, or a disconnected/blocked vapor line between the VMV and the FTPT."

P0455 is what I'm getting.

The 'diagnostic tree' would be most interesting. Don't know when evap controls first incorporated electrical devices but this is the first time ever I've had an issue with one.