Simple Fuel Cap

Sierra_Hondo · January 17, 2019

I was surprised to see that my 2018 Sierra 1500 SLT didn't have a fuel cap but instead had a self sealing fuel filler.

As soon as I saw the filler it looked like a nice trap for dirt and water.

As tight as the fuel door is -

Water and dirt have been getting behind the door -

I read here somewhere here that a 2 inch PVC cap would fit right over so I picked one up for $2.00 at my local Ace Hardware and it fit over the filler nicely-

I bought the cap that is not threaded but smooth on the inside -

The cap does not seal the tank but does a great job of keeping water and debris out of the fuel filler throat.

TXGREEK · January 17, 2019

Problem you may face with this is that the flapper allows your tank pressure to escape as needed. I’ve read others that have experienced problems when attempting to modify engineered automotive parts especially with fuel door

Sent from above

CajunFries · January 17, 2019

Look for a rubber cap. I got some off of eBay for couple bucks. And it fits nice and tight.

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Sierra_Hondo · January 17, 2019

On 1/17/2019 at 2:25 PM, TXGREEK said:

Problem you may face with this is that the flapper allows your tank pressure to escape as needed. I’ve read others that have experienced problems when attempting to modify engineered automotive parts especially with fuel door

Sent from above

Yeah, I had thought about that and why I liked that while it fit it did not seal the filler area ie: there is some space between the cap & neck allowing airflow into the tank. Express pressure in the tank should vent through the charcoal canister and the emissions system IIRC.

If it becomes an issue a horizontal hole drilled into the side of the cap would eliminate any venting issues while still blocking debris.

The PVC cap is more of a loose fitting cover than a sealed cap.

Edited January 19, 2019 by Sierra_Hondo

CajunFries · January 17, 2019

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Retired Bob · January 17, 2019

2" rubber caps can also be found at Lowe's and at Home Depot.

Penguin VII · January 17, 2019

Correct me if I'm wrong here but there is a fuel filter between the tank and the engine right? Unless you're backing up way to far at the local marina I don't see how this can help much. You can't get much water in there I'd imagine.

SS502 · January 17, 2019

27 minutes ago, Penguin VII said:

Correct me if I'm wrong here but there is a fuel filter between the tank and the engine right? Unless you're backing up way to far at the local marina I don't see how this can help much. You can't get much water in there I'd imagine.

Way more than I care to let go in...every time I fill up I grab a paper towel and wipe that area because there is always something waiting to dribble on in. Then I use the paper towel to wipe off my exhaust pipes since they accumulate soot.

Oh and no you’re not wrong there is a filter but why let stuff in if you don’t have too?

Edited January 17, 2019 by SS502

ftwhite · January 18, 2019

I think I get the motivation, but with three doors: the body, the outer visible door, and another inside the neck; how would any water/dirt/dust get past both? I certainly agree it won't get past all four once a new cap is added, but as I learned the hard way with a bottle of fuel treatment, since the neck on the bottle wasn't long enough, the treatment fluid from the bottle went in past the first door, and then spilled all over the ground under the truck because it didn't successfully prop open and get past the second door. If that didn't get in there, and am not convinced water and dirt inside the fuel door is going to either.

But, I'll admit, I use a catch can, and not everyone agrees that is needed either :-) Still cool to see the solutions people come up with.

SS502 · January 18, 2019

8 hours ago, ftwhite said:

I think I get the motivation, but with three doors: the body, the outer visible door, and another inside the neck; how would any water/dirt/dust get past both? I certainly agree it won't get past all four once a new cap is added, but as I learned the hard way with a bottle of fuel treatment, since the neck on the bottle wasn't long enough, the treatment fluid from the bottle went in past the first door, and then spilled all over the ground under the truck because it didn't successfully prop open and get past the second door. If that didn't get in there, and am not convinced water and dirt inside the fuel door is going to either.

But, I'll admit, I use a catch can, and not everyone agrees that is needed either :-) Still cool to see the solutions people come up with.

I use a catch can too. Next time I go through rain or the self serve cars wash (sprayer only) I’ll grab a picture. Not sure what you mean by three doors but regardless, when it rains hard and I go to fill up, the flapper (that replaces the standard fuel cap we used to screw on until it started clicking) had water puddled up and it’s not much but it’s maybe a 1/2 teaspoon? If I just push on the flapper that water (and dirt) just drains right into the filler neck. I’m sure it gets filtered and whatnot but for $2.00 why not put a little somewhat loose fitting (let’s it vent) cap on there to prevent the water/dirt from ever getting in there? You run a catch can as a preventative course of action and they cost a whole lot more than a rubber/pvc/plastic or even a machined aluminum cap does. I’m picking one up today. Not saying you’re wrong, just using the same thought process as me buying my RXP catch can ?

Edited January 18, 2019 by SS502

Sierra_Hondo · January 18, 2019

SS502 nails it.

It's just a simple measure to keep water & dirt (that will go into the tank when the nozzle is inserted) from accumulating in the filler neck.

6_2LTZ · January 18, 2019

I went through the car wash one afternoon when it was above freezing. A few hours later the temp dropped below freezing before the truck fully dried. The next day I went to fill up and I didn't get 2 gallons pumped in the time it should have been filled. I had put the truck inside the garage for a couple hours to thaw it out since it wasn't going to be above freezing for days.

Fast forward to two weeks later and I go to fill up and the gas cap is buried under snow. The whole area was packed with hard icy snow. There should be a cover of some sort. I never had these issues with my 14.

Penguin VII · January 18, 2019

Not doubting personal experience here, just surprised is all. Personally I've got a cap and I'm happy with it. I wonder if there is a easy way to swap back to the old style caps, seems like the best possible option if you're concerned, but a cover is cheaper for sure.

BillK01 · January 18, 2019

Here is my $4.49 solution from my local hardware store. As an added bonus I have a nice shiny new stainless steel hose clamp I can use for some other project in the future!

Edited January 18, 2019 by BillK01

SS502 · January 18, 2019

11 minutes ago, BillK01 said:

Here is my $4.49 solution from my local hardware store. As an added bonus I have a nice shiny new stainless steel hose clamp I can use for some other project in the future!

So a 2 inch cap...I like it.