Quick & Easy "Fix" for "Capless Fuel Systems"

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Lake Havasu City, Arizona
A while back I started the thread below. I was getting a "Check Engine" light, and wanted to get a scan tool to read it. I bought a Foxwell, and it gave me a P0456 Code. "Evaporative Emission System Small Leak Detected".

I cleared it with the reader, and life went on. A couple of weeks later the exact same code reappeared. I did a little research, and found out that a lot of these "Slight Leak" codes get thrown by these "Capless Fuel Systems" getting dirty.

My 2015 Jeep Grand Cherokee is one of them. As it turns out, small amounts of dust, gunk, and crap can accumulate over time, in and around the gates, trap doors, and seals that make up these unnecessarily complicated things.

If they don't seal properly, you'll get the above code in many cases. There are several Youtube videos on this problem, because it's so common. The fix is really simple. You wipe out any visible dirt or dust that has accumulated around the filler port. (I used a rag saturated with Denatured Alcohol).

Then spray the lube of your choice around the opening. Some guys use a silicone based spray. Others like myself used LPS Pre-Solve, or else plain old WD-40 will also work just as well. (Because a small amount of this will likely get into the fuel tank, I wanted to use a combustible solvent).

Then, while using the funnel that all new cars are supplied with in order to add fuel to this overly complex system should you run out, you push it in, and pull it out several times while spraying. This allows the solvent to work it's way into the gates and seals, while flushing out any dust or particulate contamination that can cause these slight leaks which throw these codes.

We're not talking about large amounts of dirt here. So it's not like you're running the risk of clogging up your fuel system. (That's what fuel filters are for). Anyway, it appears to have worked well! I cleared the code once again after I did this about a month ago, and the "Check Engine" light has stayed out thus far.

I just thought I would put this out there for anyone who has one of these type of fuel filler systems, and has experienced the same thing. I'm going to start doing this at every oil change, as a regular maintenance procedure. Funny how I never had to "maintain" a gas cap.

 
A few weeks ago, I got a CEL in the Altima(conventional gas cap) in my signature and the code read P0456; the same as yours. Several times, I was also getting the "Loose Gas Cap" banner in my dash screen prior the getting the CEL.
Like yourself, I also cleaned the area inside the filler tube where the cap screws in and in my case, the gas cap threads & O-ring. I lubed similarly to what you suggested and thus far it's been Okay. 🙏 If this keeps up, I will just replace the cap.
My daughter's new Civic in my signature is a capless system and I will to the same as you.

THANKS for posting! 👍

CB
 
Just going to point out plenty of vehicles have issues with conventional gas caps too... Sister had several GM products they would routinely borrow my scan tool to turn off the code due to gas cap problems (on multiple vehicles).

Pros and cons with any type of system.
 
A few weeks ago, I got a CEL in the Altima(conventional gas cap) in my signature and the code read P0456; the same as yours. Several times, I was also getting the "Loose Gas Cap" banner in my dash screen prior the getting the CEL.
Like yourself, I also cleaned the area inside the filler tube where the cap screws in and in my case, the gas cap threads & O-ring. I lubed similarly to what you suggested and thus far it's been Okay. 🙏 If this keeps up, I will just replace the cap.
My daughter's new Civic in my signature is a capless system and I will to the same as you.

THANKS for posting! 👍

CB
When I was an emissions Inspector I saw this frequently. The biggest issue is that automakers have decided that there should be 10 different fuel cap designs. Why I don't know. My neon uses a "double threaded" design with a triangular notch. Some vehicles use a single threaded fuel cap. When I had to replace it the guy at auto zone zone handed me a new one. The replacement that was listed wasn't the right cap, causing a check engine light. I returned it went to advance auto and their system showed the correct fuel cap.
 
Wife's 2014 F150 work truck had a hard life always parked outside, on dusty jobsites, minimal attention and it never had a problem with the capless fill. Maybe it's a brand problem? I've had to replace a couple of caps and lost a couple over the years so not hating the capless on the GMC. Thanks for the heads up.👍
 
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Just going to point out plenty of vehicles have issues with conventional gas caps too... Sister had several GM products they would routinely borrow my scan tool to turn off the code due to gas cap problems (on multiple vehicles).

Pros and cons with any type of system.
True. However for $15 or $20 bucks tops, you can buy a new gas cap for most any vehicle, and happily motor on. I don't even want to think about what a dealer would charge, if one of these capless contraptions took a dump, and the entire unit had to be replaced.
 
Great advice I never had a problem with that however my Jeep and the F-150 are capless and now I might use this as preventive maintenance when it warms up around this god-forsaken cold climate I live in.
 
Here's a vid from a BITOG favorite Ford tech. Skip to 2:00 where he basically does what Bill did. Also a link to a Ford OEM locking cap as mentioned by @zzyzzx


Apparently some PVC plumbing caps will fit over the neck and keep dirt out. Looks a bit hillbilly.
main-qimg-c5a189ddb924a076a5e7526cf1a61680-lq
 
Here's a vid from a BITOG favorite Ford tech. Skip to 2:00 where he basically does what Bill did. Also a link to a Ford OEM locking cap as mentioned by @zzyzzx


Apparently some PVC plumbing caps will fit over the neck and keep dirt out. Looks a bit hillbilly.
main-qimg-c5a189ddb924a076a5e7526cf1a61680-lq

That is exactly what I did. (I was a little more generous with the spray lube).
 
Yeah i don't trust the gas tank door seal. I work in dusty environment and there's dust settled in the door jams behind the seals.
**** now something else to worry about.
 
https://accessories.ford.com/products/locking-fuel-plug
Part No: 8U5Z9C268B

LOCKING FUEL PLUG​

locking_fuel_plug_01.jpg



5.0 out of 5 stars Works great, add a thin rubber home-made gasket to seal vapors!
Reviewed in the United States on July 27, 2022
I added due to vapor error code. Added this plug and made a thin rubber gasket (gasket was made from 1/16" x 2" rubber from Amazon, took a while to get the correct shape needed. I then cleared "code" from dash (do this using a third-party diagnostic tool or use the "disconnect" battery method. FYI: I'm still replacing the fuel neck with OEM-part upon arrival but until then..., this is a great cheap fix! Thanks everyone for the information that you have provided in assisting me, in solving my issue!!!
 
One more thing that needs to be mentioned, is under NO circumstances should you ever attempt to stick a hose down the filler neck with these types of capless systems, in some attempt to conduct siphoning. If you do you'll never get it out.
 
When I was an emissions Inspector I saw this frequently. The biggest issue is that automakers have decided that there should be 10 different fuel cap designs. Why I don't know. My neon uses a "double threaded" design with a triangular notch. Some vehicles use a single threaded fuel cap. When I had to replace it the guy at auto zone zone handed me a new one. The replacement that was listed wasn't the right cap, causing a check engine light. I returned it went to advance auto and their system showed the correct fuel cap.
If I have to replace my fuel cap due to the CEL returning, I will only use an OE. When it comes to emissions, I don’t like aftermarket parts. Not even a gas cap.
 
Sounds like a good idea and could be part of a car wash routine.

I have a regular cap but twice a year I open the fuel door and wipe out the area with detailer. Pollen tends to build up in mine.
 
I have a 2020 Silverado with the capless fuel fill. I just got a Curt rubber hitch ball cover of the correct size, cut it in half and it fits perfectly over the capless filler. About $4.
 
One other thing I forgot to mention. While I don't use it very often, I found out when the "Check Engine" light is illuminated, the remote start feature will not work on these late model Jeep Grand Cherokees. (The engine will start normally when the remote start button is pressed twice on the FOB. It will then run for about 10 seconds, then shut off).

When you get in the car, you then get a message on the dash that says, "Remote Start Rejected, Press "START" To Reset". The problem is doing that will reset nothing as long as the "Check Engine" light is illuminated. (The engine starts and runs normally by conventionally starting it, by pressing the button on the dash with your foot on the brake).

It's my understanding that Chrysler Jeep has 2 types of "Check Engine" lights. A solid light that remains on. And a flashing light that signifies a major problem, and to get the vehicle serviced immediately to avoid any damage.

The P0456 Code..... "Evaporative Emission System Small Leak Detected", is considered to not be a major fault, and produces a solidly lit "Check Engine" light. I don't know about Ford or the other manufacturers systems. But this was yet another reason why I wanted to get rid of this code, and put the light out once and for all.

I have no idea why this should disable the remote start feature... But it does... At least on the Jeep.
 
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