Solved Possible answer to "permanent" P0455 on '97 4.0 Explorer

[allmyEXes]

I've posted a thread somewhere on this Forum about the P0455, but I'll just start fresh.
Some time back I spent quite a bit of time trying to find what is causing p0455,"evap system Gross Leak detected". I looked all over the engine. I had the inner apron out looking at lines and connections for a broken hose or a hole in a line. I even used a smoke machine. Burnt baby oil smells kind of nasty. Next time I'm going to use leftover Panama jack tanning oil, I bet it will smell better.
Tuesday, when I put about 11 gallons in, a 2 ft puddle formed on the concrete. Someone else noticed it, so I don't know how long this has been happening. The puddle was about 2 ft forward of the gas fill hole that the PO previously knocked out to get his full tank of gas back out after the 4.0 SOHC left front chain guide broke. I wonder what else that he broke or other possible ways that he might have tried to get gas out of it. The mileage is really good on this truck. We are getting 20 plus mpg and that makes me feel like it is only a leak that happens when putting in gasoline. We only put in about 11 gallons, so it wasn't a getting it too full situation. Or maybe this is a new leak has been caused by a rat or squirrel.
Any ideas? I hope to get under it Sunday.

 

[Pete Deering]

I've posted a thread somewhere on this Forum about the P0455, but I'll just start fresh.
Some time back I spent quite a bit of time trying to find what is causing p0455,"evap system Gross Leak detected". I looked all over the engine. I had the inner apron out looking at lines and connections for a broken hose or a hole in a line. I even used a smoke machine. Burnt baby oil smells kind of nasty. Next time I'm going to use leftover Panama jack tanning oil, I bet it will smell better.
Tuesday, when I put about 11 gallons in, a 2 ft puddle formed on the concrete. Someone else noticed it, so I don't know how long this has been happening. The puddle was about 2 ft forward of the gas fill hole that the PO previously knocked out to get his full tank of gas back out after the 4.0 SOHC left front chain guide broke. I wonder what else that he broke or other possible ways that he might have tried to get gas out of it. The mileage is really good on this truck. We are getting 20 plus mpg and that makes me feel like it is only a leak that happens when putting in gasoline. We only put in about 11 gallons, so it wasn't a getting it too full situation. Or maybe this is a new leak has been caused by a rat or squirrel.
Any ideas? I hope to get under it Sunday.

There is a vapor line in the driver side frame rail. It starts at the fuel tank to the EVAP Canister, runs the frame rail to front , to the purge valve, then to the engine.
My vapor line was rusted out in the frame rail under driver side rear door.
The fuel supply and return lines are stainless steel. The vapor line is carbon steel.

 

[J_C]

Tuesday, when I put about 11 gallons in, a 2 ft puddle formed on the concrete... The puddle was about 2 ft forward of the gas fill hole that the PO previously knocked out to get his full tank of gas back out after the 4.0 SOHC left front chain guide broke.

I don't understand this statement. Can you elaborate on gas fill hole and on knocked out?

On my '98, to siphon gas out, I can just disconnect the rubber hose between the filler tube and the tank, at the tank nipple. I'm wondering if you just have a rusted out pinhole in the metal filler tube and gas is running down the outside of that until it drips off at the tank?

It may leak gas only when putting in gas, but that same leak spot is probably causing the lack of vac that sets that trouble code.

 

[allmyEXes]

@J_C c Where the gas cap is screwed into the tank filler neck, when the cap is removed, normally you can see the spring-loaded one-way flapper, someone has reached down in there with something just small enough, like a short barbell rod? and pounded with a hammer until that much of the fill neck broke. The flapper is gone and there is a big opening. As I type this, I see why that may be what is making it a little harder to get gasoline into it. I have to run the nozzle locked on medium flow instead of full on.

 

[Pete Deering]

@J_C c Where the gas cap is screwed into the tank filler neck, when the cap is removed, normally you can see the spring-loaded one-way flapper, someone has reached down in there with something just small enough, like a short barbell rod? and pounded with a hammer until that much of the fill neck broke. The flapper is gone and there is a big opening. As I type this, I see why that may be what is making it a little harder to get gasoline into it. I have to run the nozzle locked on medium flow instead of full on.

It could also be the purge valve is bad ( not in the open position) when key is off and filling with gas.

 

[J_C]

Okay so I imagine that enough stress on the top of the filler tube, especially at its age, could cause a leak. I assume that it's not so deformed that you also have the gas cap itself leaking from a bad seal.

I'm not necessarily suggesting doing it instead of further looking around for the leak, but if you disconnected the rubber hose connecting the filler tube to the tank, at the tank, then sealed the open tank nipple air-tight, just as a test, this should make the code go away if the leak is in the filler tube.

I don't know how long it would take for the code to clear itself, think I'd clear it with a scan tool to expedite testing. I also don't know what I have lying around that I'd use to seal that, maybe a nitrile work glove or LDPE plastic trash bag, and strap of some sort... possibly just a nylon wire-tie with a wad of glove or bag where it cinches together and has a potential gap, or over top of a wide rubber band like the ones that come on my grocery store asparagus, lol. Maybe the rubber band alone would be enough. Obviously I don't mean to drive it around, just driveway testing.

I do think it should be easy enough to spot whether the gas is leaking, at least whether it's coming out of the filler tube without resorting to that, without jacking it up, just head under the rear and a flashlight while a helper is dumping fuel in from a gas can, unless the rate from a gas can is not high enough to put gas where the leak is. I'd get it leaking first, to decide where to put my head so I don't get gas all over it, especially in my eyes.

 

[allmyEXes]

I/we just got back in from a 150 mile trip. I put in $30 ($2.56 a gallon!) and I was watching with the nozzle on and off. It is coming from the area that could be the rubber hose connecting the filler neck and tank. So, the P0455 and the fuel leak may be two different issues.
Thank you guys for the input. I'm not sure what I can do working on it on the ground, but it looks like the left rear wheel will have to be removed regardless. If I had an undamaged filler neck, I would change it while it is loose anyway. We have rain coming through mid-day Sunday so I will look at it at some point. The lift at work is still occupied until almost Christmas break. Thanks.

 

[J_C]

Anywhere fuel leaks out is a hole/gap/etc. The same hole/gap/etc is almost certainly letting some air in when the system is trying to maintain vac. The question is whether it is losing enough vac, from the area it's leaking fuel, to trip the code or if there is a 2nd leak too.

 

[allmyEXes]

Maybe it was a small hole causing the code and it has grown into a hole big enough for a fill up leak. I have located a new filler neck unless one of you guys has a parts truck with a good old one laying in the back after taking out a tank. Anyone let me know in the next two weeks. It will be that long before I can fix it properly. I think that about 8 oz is dripping out for every 11 to 12 gallons going in. Picture of new one. Does this look correct?

 

[J_C]

The pic looks like it maybe could be right, but I'd have a better idea after you bolted it on and held the hose up to it.

 

[allmyEXes]

@J_C

On my '98, to siphon gas out, I can just disconnect the rubber hose between the filler tube and the tank, at the tank nipple. I'm wondering if you just have a rusted out pinhole in the metal filler tube and gas is running down the outside of that until it drips off at the tank?

The larger fill hose fitting welded to the tank?
On the ground lifted 4", is it possible to reach the clamps to remove the filler neck/vent tube and hoses? When I/we removed my '92 4 door tank, it was on the lift and we were standing under it. I don't want to remove the tank in this white '97. Just replace the rubber hoses and damaged filler neck. Anyone parting out these trucks?

 

[J_C]

I have removed my rubber hose on my '98, at the tank to siphon gas. No lift needed to get the clamp off and pull the hose. I wasn't pulling the other hose so don't know about that one.

 

[allmyEXes]

@J_C Here is a picture of the filler neck.

 

[J_C]

I don't know if that's a problem or not, I mean it looks round still, like the cap might seal as long as it threads on tight.

 

[allmyEXes]

I still haven't followed up on this little problem. Honestly I don't think/remember about it unless I'm with my wife and fill up her truck for her. If the leak is as simple as a fill tube rubber hose that connects the filler neck to the tank, that would be enough to cause a vacuum leak and present a p0455 code. The code is really a secondary issue at the moment.
In order to be efficient and not have to get down up under the left rear twice, what is the size of the fill neck hose? I'm inclined to think that is what the problem is and not a rusted out filler neck tube(pipe). This truck hasn't seen any road salt and is not rusty.
Thanks in advance on the tube size and I'm going now to look on Rockauto to see if they might offer the rubber hose.

 

[allmyEXes]

I looked to see if Rockauto offers hose and I haven't found it yet. However, I did find the hose sizes for the filler neck. Bellow is a snip it capture
of the filler neck specs that has to do with it. 1" id I suppose. It seems small doesn't it?,

 

[Pete Deering]

I looked to see if Rockauto offers hose and I haven't found it yet. However, I did find the hose sizes for the filler neck. Bellow is a snip it capture
of the filler neck specs that has to do with it. 1" id I suppose. It seems small doesn't it?,
View attachment 450580

There are two hoses. One for the filler, and one for the overflow.

 

[allmyEXes]

@Pete Deering Picture in post #9.
I don't think it the vent tube part of the assembly that is leaking. That tube is on the side. I can barely dribble fuel into the filler neck and it starts drip about 1 second apart.

 

[Pete Deering]

@Pete Deering Picture in post #9.
I don't think it the vent tube part of the assembly that is leaking. That tube is on the side. I can barely dribble fuel into the filler neck and it starts drip about 1 second apart.

The small hole could be at the flange uses duct tape. To see if it get removed from the gas.
Try this company.

Filler Neck Supply: Gas Tank Hose | Fuel Filler Necks

Filler Neck Supply Specializes In Fuel Filler Necks & Gas Tank Parts For Utility Body & Flatbed Conversions, As Well As Radiator Filler Necks, Secure Internet Checkout!

www.fillernecksupply.com

1. What you can try. Wrap the pipes in plastic wrap.
And if fill with fuel.
2. It also could be from the vent canister line or the vapor line.

Search the forum. There is a writeup with pictures.

How To: Replace Filler Neck/Tubing on 2nd Gen​

 

[allmyEXes]

Ordered
1" ID fuel hose