P0440 Fixed!

[fourfive]

Short answer fix for my P0440: Replaced overfill check valve that had a small leak on top of my gas tank. This part only applies to 2001-2002 4runners.
Overfill check valve: 77390-35010
======================================


Symptoms:
1. Certain gas pumps would shut off after filling for a few seconds.
2. A few thousand miles after getting the P0440 code, there was a very faint gas smell I would occasionally notice after parking my 4runner in my parking deck or at idle with my window down. Never noticed any gas smell if my windows were up.

Timeline:
May 2016 I get a cel and scan tool pulls up P0440 (general code for evap system issue). I installed a new Toyota gas cap just for the heck of it and cleared the code. A few weeks later the cel comes back as P0446. Cleared it just to see what would happen and cel came back as P0440 about a month later.




I used the FSM as my guide for troubleshooting my evap system. I started by troubleshooting the areas that seemed a little more straight forward via the fsm.

1. My charcoal canister & VSV for pressure switching valve (attached to the canister) passed the fsm pressure and vacuum tests. The charcoal canister is located above the spare tire for 2001-2002 4runners and for 96-00 it is under the hood along the driver side fender.
Tools used for testing:
1. A couple feet of 1/4" hose
2. various sizes of vacuum plugs
3. mityvac brake bleeder (has pressure & vacuum option)
4. air from my lungs
5. 9v battery
6. multimeter


2. I tested my gas tank components next due to the occasional mild gas smell. Since I was having issues with my air compressor I ended up just blowing into the various ports the fsm suggested using a 1/4" tube. I could hear air escaping from overfill check valve on top of my gas tank (only 2001-2002 4runners have the overfill check valve on top of the tank). Since I was going to have to drop my tank to replace the overfill check valve, I figured I'd replace all the other gas tank components including the fuel pump. I replaced the parts Thanksgiving weekend. After replacing the parts, I didn't clear the cel to see if it would turn off on its own. About 350mi later, the cel was still on so I manually cleared it. The cel was off & no pending codes but my scan tool said it was "not ready". A total of 950mi after replacing my overfill check valve, my scan tool indicated that my evap system was "ready" & no pending codes. Passed my emissions test last week! Thanks to the write ups, dropping the gas tank was much easier than I thought. I did get blasted in the chest with gasoline removing one of the fuel lines because I didn't depressurize the fuel system enough. That sucked.

Toyota part numbers for gas tank components:
*Overfill check valve: 77390-35010
*Overfill check valve gasket: 77177-33010
Fuel pump gasket: 77169-60010
Fuel pump: 23221-46010
Rubber cushion for fuel pump: 23249-74610
or
Denso 950-0100 (950-0100 is the product number on the package but 195130 is what's actually stamped on the denso fuel pump)

Fuel cutoff valve: 77380-26010
Fuel cutoff valve gasket: 77179-26010

*The overfill check valve only applies to 2001-2002 4runners





Picture of the dirty fuel pump sender contacts before using a pencil eraser, as suggested in a couple write ups, to clean it up.



Picture of my homemade smoke machine. There are DIY vids on youtube for anyone interested in making a smoke machine. The smoke machine itself worked fine but when I had it running through my evap system, I never saw any smoke...possibly because I was outside making it harder to see the smoke escape from a very small leak on top of my gas tank.

 

[LittleCaesar]

I love the homemade smoke machine. I guess you wouldn't have a link for it possibly?

Glad you found the problem.

 

[fourfive]

Thanks man, huuuge burden off my back getting that evap issue resolved.

I used a few different youtube videos as a resource when I made my smoke machine. I initially started very basic using a paint can & incense which worked fine but then made things a little more "high tech" for convenience.

vid 1
vid 2
vid 3
vid 4 If you want to use a flowmeter for leak testing

Very general parts list:
1 gallon paint can

assortment of 1/4 air compressor accessories from harbor freight: couplers, quick connect fittings, etc

1/4" Coupler x 1/8" NPT Male Thread (2) if using the dwyer flowmeter

dwyer flowmeter

3/8 clear tubing ~10'

24 gauge resistance wire that I got from a local vapor/tobacco shop

2 insulator binding posts

mineral oil (to increase smoke production)

propane gas regulator 0-10psi

oil lamp wicks

insulated alligator clips

Air source: having an air compressor is a nice luxury but I was able to make a bicycle tire pump work in a pinch when I had air compressor issues.

 

[LittleCaesar]

Definitely a DIY project to tackle for the new year. I have wanted one when trying to chase down a vacuum leak on autos. I saw one on the Snap On truck last year and went to grab it until I realized it lists for over $800. Not cost effective for someone who isn't a mechanic.

 

[WallyWest]

Thanks for the write up, and the home made smoke machine stuff. I think I will make one of those.

Got a 440/446 code myself that I've been ignoring. No gas smell, and the CEL isn't predictable. I clear it and it might come back on in 40 miles, or it might stay off for 400 miles. I'm thinking it could be the VSV sticking now and then, due to the random nature of the code being set. But if I go tearing things apart back there I might go ahead and replace the stuff you did on general principles.

:thumb:

 

[SupaSupra]

Glad you posted this. I'm having this exact same issue as you.

 

[fourfive]

Thanks for the write up, and the home made smoke machine stuff. I think I will make one of those.

No problem. I initially started with a very basic smoke machine using incense to produce smoke which worked fine & was really simple and cheap to make but the more I leaned about smoke machines I started adding to it so it would function similar to a professional one. That required a little more time and money but still much cheaper than buying a $800+ professional smoke machine. There's sellers on ebay selling homemade smoke machines from $100+ but they didn't have certain features I wanted like a flowmeter.

I was quoted about $100 for a smoke test at local shops. You could basically build your own smoke machine including a cheap air compressor from amazon for that much. From my limited experience, I've found that when performing a smoke test to find an evap or vacuum leak, it is not uncommon for there to be multiple smoke tests needed to accurately find a leak especially if it is a small leak or if there are several small leaks. Because of that, I felt I would benefit more to have my own so I could run smoke tests as needed until the leak/leaks were identified rather than constantly taking it back to a shop.

 

[fourfive]

Added some pages from the FSM that I followed for troubleshooting my charcoal canister and fuel tank for evap leaks.


Charcoal canister and VSV for pressure switching valve location for 01-02 4runners)



Disconnecting vent line hose from canister (fitting can be difficult to remove)



I used a 9v battery and a multimeter to test the VSV for pressure switching valve



How to pressure & vacuum test charcoal canister. You can use a hand held brake bleeder with pump & vacuum option or air from lungs.



Overfill Check valve testing



Fuel tank & filler neck testing for airtightness



Check for proper ventilation on air inlet line on charcoal canister

 

[dan_from_the_south]

Thanks for all this great information.

I've got P0440, too. I've got a few months until emissions are due, so I'm hoping to get this figured out without having to make a trip to the shop.

You mention that you heard air escaping from the overfill check valve at the top of the tank. Was the sound pretty obvious? Do you think you would have been able to/did you see smoke coming from that area?

P0440 has plagued me for a number of years now. I actually had a new charcoal canister put in before emissions were up for me last time (2 years ago). I passed the emissions, but the code came back a couple weeks later. I've had smoke tests done before, but they never found anything.

I too can smell gas when I'm around the tank, so I think I may have a similar situation to you.

 

[fourfive]

The sound of the air escaping was faint but pretty clear. It was about as loud as air escaping from a small hole in a straw if you were to blow through it. I would imagine it would be tough to hear if there was even a little extra background noise. It's POSSIBLE that I may have been able to see smoke if I did the smoke test indoors without any wind but I still think it would be difficult to see if it wasn't a decent size leak such as cracks in a hose or a loosely fitting hose.

 

[crazy larry]

subscribed. I just got this code yesterday...

 

[crazy larry]

for the record: tightened my gas cap, pulled the EFI fuse for 30 seconds, started up, no CEL. Happy days are here again.

 

[fourfive]

for the record: tightened my gas cap, pulled the EFI fuse for 30 seconds, started up, no CEL. Happy days are here again.

Did you check for pending codes? Replacing the gas cap and clearing the code worked for me initially but CEL came back a few weeks later.

 

[jkfuel]

Disconnecting vent line hose from canister (fitting can be difficult to remove)
View attachment 232380

Can anyone help with this? I am pinching the "A" and nothing moves or flexes. Should the "tabs" fold inward allowing you to remove the hose?

 

[fourfive]

If I remember correctly, when you pinch the hose, the tabs on the hose SHOULD expand away from the fitting allowing you to wiggle the hose free. You can use a small 90 degree pick (few bucks from HF or amazon) and work it around the house to help loosen it up &/or use some pliers to GENTLY apply a little more 'squeeze' to the hose.

 

[jkfuel]

If I remember correctly, when you pinch the hose, the tabs on the hose SHOULD expand away from the fitting allowing you to wiggle the hose free. You can use a small 90 degree pick (few bucks from HF or amazon) and work it around the house to help loosen it up &/or use some pliers to GENTLY apply a little more 'squeeze' to the hose.

Thanks for the clarification. I ended up pushing on the END of the tabs which allowed them to fold outwards making it easier to pull off. You do NOT want to break these- replacing the whole thing looks like a pain. Thanks again.

 

[Bud4me0007]

I have the same codes myself. Going to take a look at it some time this week.

 

[jkfuel]

I have the same codes myself. Going to take a look at it some time this week.

Let me save you some time, go to the dealer and pay whatever the diagnostic fee is and save yourself the headache. Don't just replace parts like I did as the canister alone will be about 300-350.

Mine ended up being the canister filter and the fuel filler neck which were somewhat frustrating to replace.

 

[JayRolla]

Let me save you some time, go to the dealer and pay whatever the diagnostic fee is and save yourself the headache. Don't just replace parts like I did as the canister alone will be about 300-350.

Mine ended up being the canister filter and the fuel filler neck which were somewhat frustrating to replace.

Why would you do that when you can just buy a $10 odb2 adapter. Pull your own codes and follow the Toyota FSM. Its how they do it. Even dealers sometimes throw parts at CEL's.

You can save a ton of money diagnosing it yourself and you learn something along the way.

 

[fourfive]

Why would you do that when you can just buy a $10 odb2 adapter. Pull your own codes and follow the Toyota FSM. Its how they do it. Even dealers sometimes throw parts at CEL's.

Very true. Especially when the evap leak is so small that it is missed during the first 1 or 2 smoke test attempts & because trying to diagnose any further would be time consuming parts are thrown in resulting in $$$ & the same CEL.