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Dodgerench
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3130
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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I have a 04 dodge neon, I contiuiouly get code P0441 or P0440.

Customer Question

I have a 04 dodge neon, I contiuiouly get code P0441 or P0440. I have replaced the purge valve, leak detecton pump. I have inspect the canister and it appears to be good. I have smoked the tank and all the vacuum lines appear to be sealed. What have I missed?
Submitted: 4 years ago.
Category: Dodge
Expert:  Dodgerench replied 4 years ago.
HiCustomer welcome to Just Answer!.

From what I can see, you haven't missed much. One of the things I'd like to know is if vacuum is actually being applied to the evaporative system during its test and whether the system holds this vacuum.

Your smoke testing will tell if there's a split hose or some sort of leak that shows up under pressure. but the system actually tests itself with vacuum. Something as simple as a gas cap that doesn't seal on the vacuum side might be what's causing your continued grief.

Also make sure that the new purge solenoid opens when actuated and that it has a strong vacuum source supplied to one of the ports for purge/ testing purposes.

To test, you can connect a vacuum tee to the purge solenoid hose connector that passes to the tank and connect a vacuum gauge. Apply vacuum to the tank and watch to see what the maximum vacuum reading the system is. This is typically about 1" Hg, but will be difficult to measure with a typical 0-15" Hg vacuum gauge.

If the system won't hold vacuum, but no pressure leaks are present, replace the gas cap or at least try sealing the fill tube with duct tape and retest to see if it makes a difference.

Other possibilities would be with the NVLD unit itself or with wiring on the circuit. If the PCM can't see the NVLD switch state change when purge flow begins, it's going to set these two codes.

The wiring to the NVLD is fairly exposed and may have taken a rock hit at some time. Pulling on each of the wires individually, you can find a bad spot when the wire insulation snaps because the copper conductor is no longer intact. Check at all exposed wire toward the rear of the car.

Ed
Customer: replied 4 years ago.

Ed, Thanks for your answer and I will check this out tomorrow, a follow up quesiton, dont want to show my ingorniance here, but what is the NVLD?

 

I have replaced the gas cap, it was the first thing I did. Also checking the purge solenoid, will it actuate immediately or when?

 

Thanks

 

Mike

Expert:  Dodgerench replied 4 years ago.
Hi Mike!

NVLD stands for natural vacuum leak detector, what you would normally consider to be a leak detection pump. In this case, it's mostly a passive device that has only two moving parts and sits in the place where you'd expect the LDP to be... behind the RR wheel.

It has an electrically operated valve that opens a vent for operation when it's NOT testing and then there's the vacuum switch used for detecting purposes.

Its theory of operation is based on the gas law... that a gas or vapor in a sealed vessel will lose pressure as temperature drops. So the NVLD seals the evaporative system for overnight leak testing and also seals for the invasive purge flow testing it does with the engine running.

With the system sealed, purge is turned on. This act will draw vapors from the vapor canister and will also cause a drop in evap system pressure, something that the NVLD should pick up as its internal switch closes.

The NVLD is located behind the right rear wheel, kinda stuffed up into the under-trunk area.

Your purge solenoid operates almost continuously once the engine is warmed up and the engine has been running for at least a minute. It's completely variable, able to allow extremely small amounts of purge flow all the way up to full open flow depending upon the circumstances.

If you were to disconnect the 90-degree fitting on the back side of the engine that connects the steel purge line to the nylon purge harness, it would probably be the easiest place to feel purge flow come on. Disconnect the hose and put your finger over the tube after the engine has been running a few mintues to check for vacuum or just use a gauge. Flow rates will be fairly low at idle, so don't expect TOO much... just that it happens.

With the cap being new and if you've already replaced the NVLD, we might be looking at a wiring problem if there are no pressure leaks present. See what you can find on the 3-wire connector back at the NVLD and we'll go on from there.

Ed
Customer: replied 4 years ago.

Thanks Ed that clears the NVLD up a little bit, I will check all the wiring tomorrow and hopefully that will be the problem, other wise I just may blow this thing up!!!!!

 

Thanks and will let you know how it goes

 

Mike

Expert:  Dodgerench replied 4 years ago.
Sounds good, Mike. Talk tomorrow!

Ed
Customer: replied 4 years ago.

OK Ed, here is what I have done so far today. Mind you, I have reset the computer and have not code present at this time, however, in a couple of days I believe the light will trip.

 

At the purge solenoid I have 12 volts going in to it, since I dont have a schematic I will assume that the other wire is a ground of some type. Anyways, I hooked up a vacuum gauge from the line between the tank and solenoid. After about 1 minute of run time I was getting a steady 20in hg. , shut the engine off and it held the vacuum. I then went to the NVLD and checked the 3 wires for any kind of breaks all appeared to be good. I then started the vehicle up and I could feel the NVLD click it also clicked went I shut down the engine. Now, it only clicked when I started the engine not just turning the vehicle on with out engine running. I went back to the steel line that ran back to the tank and tried to pull a vacuum. I have a hand pump to do this with and at no time was I able to get any kind of vacuum. I blew though the hose and could hear air at the fuel inlet only, no where else. I tried the tape on the fuel inlet like you stated and still no vacuum could be created. At this time I have check everything and I am at my wits end. I am pretty good at stuff like this but the only thing I can even think could be a problem would be the ECU, however, I pretty sure I ruled that out because I disconnect the wires on the NVLD and the check engine light come on.

 

What else can I try

 

Mike

Expert:  Dodgerench replied 4 years ago.
Mike, I have to agree... you are pretty good at this stuff! We'll find it.

graphic
graphic

See if you can put a hose tee in between the purge solenoid and the steel line to create and measure vacuum once the purge solenoid opens. You'll have to clamp the vent hose from the NVLD to hold this vacuum because the NVLD will be in vent mode with the engine running. Even when shut off (closed) it's not able to hold more than about an inch of vacuum so I just like to clamp off the farthest-back hose with some needle-nose Vice Grips and be done with it.

The only consistent leaks I can recall on this system is also the hardest hose to see or get to, being the one that connects the steel line to the vapor canister all the way back at the axle area by the way.

Fuel being what it is, it's not gonna allow a high vacuum to be held for long because its inherent volatility will outgas and replace the vacuum with fuel vapors as you watch the gauge. Stop at about 2 or 3" Hg to avoid collapsing the tank, yet still have a good bit of vacuum to use for testing. Do the testing in the coolest possible temperatures to keep outgasing to a minimum.

The NVLD wiring diagram I pasted might help you a bit if it comes to where we need to test the circuits out. I'm in agreement that since you saw the MIL come on with a connector disconnect that things are probably OK.

Talk in a bit,
Ed
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3130
Experience: 30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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Customer: replied 4 years ago.

Ed,

 

I hooked a tee up between the steel line going to the purge canister and the purge solenoid. After about 1 to 2 minutes of run time I recieved no vacuum reading. I disconnected the hose going into the purge canister and cover it with my thumb and was getting engine vacuum. I hooked it back up and recieved nothing. About 5 minutes later I started to get a vacuum reading of 2 to 3 in. hg. as soon as I shut the engine off i would lose the vacuum. I clamp the hose going to the NVLD, again about 5 minutes of run time I started getting the 2 to 3 in.hg., I again shut off the engine and lose vacuum. Now I also disconnected the hose going out of the purge canister out to the fuel inlet. I started the the engine thinking I would get some kind of vacuum buy holding my thumb up at the nipple. I did not feel anything. What I dont understand is I get engine vacuum to the canister but nothing I can feel out of the canister. I have started the car at least 20 times since resetting the MIL, it has not come on yet. I understand that its suppose to go through 2 failed cycles before it will trip the MIL, should it have done it by now?

 

Mike

 

Expert:  Dodgerench replied 4 years ago.
It might just be the canister itself, Mike. The mounting pegs at the far right of the unit can be broken off, yet still appear OK if the break is obscured by the rubber grommets they push through.

By the way... some canister leaks won't show up on a smoke test because the canister can absorb the smoke media depending which way it comes from. If you were to reverse the direction of smoke entry, it might make all the difference. I've got a feeling this is where the problem lies.

Your medium/ large evap leak and purge flow monitors don't run immediately at engine start. I believe both wait until you've got the engine to full operating temperature so it can better handle the hydrocarbons that are being force-fed during testing.

Ed

Edited by Dodgerench on 10/25/2009 at 9:25 PM EST
Customer: replied 4 years ago.

Ed, I will check that tomorrow after I get off work, I took it off once and it looked fine, but I was checking for debre and/or fuel contamination. I did not look that close at the case itself. Ill let you know something tomorrow

 

Thanks

Expert:  Dodgerench replied 4 years ago.
That's fine. Enjoy the rest of the day!

Customer: replied 4 years ago.

Ed checked the canister today I found nothing wrong with it rechecked the hoses in the area and still found nothing wrong. At this point I am thinking about replacing the canister just to replace it.

 

The car has been driven over 150 miles with no MIL, however, my scanner pickup up a pending code of P0441

Expert:  Dodgerench replied 4 years ago.
Yep, it's coming back. It appears you're fighting a leak of some sort because you couldn't sustain a vacuum during the purge test you did with the NVLD clamped off, so it's gonna be almost certainly with a rubber hose or the canister.

When you get under there and remove the canister, check the smallest of the three hoses that connects to the steel line for cracking up near the steel line. I've seen very few problems with the Neons in places other than this one hose or if the canister got smacked by something... which usually distorts the mounting bracket and is pretty obvious.

That hose is a bear to find in the parts book by the way! I've never been able to find it myself but a JA customer located it somehow and published the part number online. I've got it written down at work, so if you wind up needing one, just let me know.

Many thanks!
Ed
Customer: replied 4 years ago.

Ed I will check the lines again I just dont see anything. I had the canister off and blow thru it. I put my thumb over the two openings and tried to blow thru it and couldnt. I look at the rubber hose pretty hard today and saw nothing, however, they are a little soft, I was able to hold a vacuum from the steel line to the canister so its not that one, the middle hose is teed and goes to the tank and vent the third hose right side goes to the NVLD and that is also a little soft. I know those should be replaced but do you think being soft could cause this.

 

Mike

Expert:  Dodgerench replied 4 years ago.
You're taking this in a systematic approach... which is just the way to do it. Keep moving the clamp farther and farther away from the vacuum source until it no longer holds and you'll have found the leak source.

Soft hoses usually aren't a problem here... it's the cracked ones that cause problems. Just wondering, what code was set when you disconnected the NVLD? You've replaced the NVLD, right?

Ed
Customer: replied 4 years ago.

Ed,

 

I didnt check the code, I just reset it after I set it off and yes I replace the NVLD, I give it a try again tomorrow and will let you know

 

Mike

Expert:  Dodgerench replied 4 years ago.
Thanks Mike. It's probably nothing significant, I'm just curious to see which code it sets so I can sort of write off certain possibilities. It really sounds like a leak of some sort so far but I was just curious.

Speaking of curiosity... did you use actual needle-nose Vise Grips for clamping? I've seen problems with commercial hose clamping devices that just don't have the squeeze that an over-center locking plier like the Vise Grip has. They allow a small amount of leakage that just plain makes you chase your tail! As entertaining as that can be with the dog, it's not so great when working on your car lol!

Ed
Customer: replied 4 years ago.

Ed,

 

OK, I think I screwed up, I was checking the vent line that goes from the fuel tank, Tees off to the canister and the fuel filler vent, anyways has I was pulling the rubber hose off the tee, it cracked. Now what I am hoping is it was cracked the whole time and me pulling on it just broke. So I am stuck now until I replace that Tee, now I think I will have to replace the entire line because the hose from the tee to the fuel tank is on of those plastic ones and it appears to be shunk onto the Tee. do you have the P/N for the line and Tee. I am really hoping this is it, the pain is I have to drop the tank now to get to the top. Good thing is I can inspect at that time. Will let you know how it all goes. Again I cant thank you enough for walking me through this

 

Mike

Expert:  Dodgerench replied 4 years ago.
That actually sounds pretty plausible, Mike. Good hoses don't crack when they're handled, so it probably had a small split on the side you couldn't see. I'm not sure, but the hose you're describing may not be serviced separately from the tank, but I'm sure it could be repaired so you don't have to drop the tank.

I'll check to see if I can find some evap hose diagrams so we'll be on the same page. Right back.

Ed
Customer: replied 4 years ago.
Im going to have to drop the tank, it goes right on top of it and I can see where it connects, thats one of the reasons I was checking is so hard, it is one of those the I have overlooked and was trying to see if I could see anything wrong with it, I did pull harsd the the hose but still I dont think it should have broXXXXX XXXXXke that anyways it is a plastic ling that appears to heat shrunk on the tee, not sure if I could cut at the tee, get a new tee and heat shrink it back on, ive never done anything like that before, anyways anything you can do thanks
Expert:  Dodgerench replied 4 years ago.
I didn't have much success with pictures but what I see on this top view of the tank makes it look like the rigid black nylon hose from the center to the canister may be removable...

graphic

It looks like a formed rubber hose, but I just can't remember there being one there. I've had dozens of tanks out and chased evap leak codes for years but when something doesn't give me problems I don't always take notice lol! Here's a rather poor underside view of the line at the canister...

graphic

If the yellowed area is what was cracked or broken, it does seem like it could be repaired with a little creative hose work. All that matters is that you maintain most of the inner hose diameter and that the system has no external leaks... pretty much anything goes.

The hose on the far left in this pic is the one I'd wondered about earlier and seems to crack only up near the steel line.

To drop the tank, do what you can to run some gas out first. It's not a hard unit to work with, but gas adds "live weight" to the thing, something that can get away from you at times when it sloshes.

I use motorcycle tie downs to support the tank when the tie straps are removed. If you can string a single tie through the center of the tank in a north-south direction, it will give you quite a bit of room to lower without it being able to get away and fall out because it tips and contacts the bottom of the car.

Take your fuel line and pump connector off first so they don't get stretched.

Going back up is handy with the motorcycle tie down as well... just push up with one arm, pull the strap with the other to hold it in place while you get the straps back on. The straps hinge at the forward part of the tank and unbolt near the axle.

Good luck!
Ed
Customer: replied 4 years ago.

yeap thats it, can i just get a comparable tee and put it in? for some reason it looked like it could have a check valve in it. I checked the evac sticker on the car and it only shows a tee, if thats the case I should be about to do something with it. I have pulled several tanks and its not that bad as long as I get all the fuel out, I tried it once with a half tank and liked to killed myself LOL anyways this things has a full tank, I'm not going to siphon that out, so thanks for the tip, let me see what i can find and I will let you know tomorrow.

 

Mike

Expert:  Dodgerench replied 4 years ago.
Sounds good. There's no check valve involved with the evap system hoses, so feel free to cobble as required!

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