Diagnosing an EVAP leak on motronic 4.4

[xtrattitude4u]

I've had an EVAP leak that has been plaguing me for quite some time now.
It started out as PO442: Small leak, then progressed into PO455: Large leak.
I was also smelling gas in the cabin after filling up the tank.
I had tested the purge valve, checked the charcoal canister, and examined all the vacuum lines (or so I thought).

The problem I found was not mentioned anywhere I looked, so I thought I should cover it extensively.
First things first. Here is my representation of the system as a whole.
This is on a 1998 S70 Non-Turbo with the Bosch Motronic 4.4 fuel system.

Evap System.JPG (55.84 KiB) Viewed 4435 times

The hollow lines are representative of the EVAP system hoses.
All the darkened areas of these hoses are suspect areas for a leak, as is the purge valve itself.
The rollover valve ended up being the location of my problem, but I'll cover how I tested everything.
The best place to start diagnosing the system is at the charcoal canister IMO.
All the hoses for the system intersect at the canister, so you can isolate the problem quickly from there.

My canister is located just inside the front bumper on the driver side.
Here is a view of the canister from underneath:

You can see the "Purge" and "Tank" hoses running along the front of the frame.
They both connect to the top of the canister with the infamous J-hoses. (a common failure point)

There is a 10mm bolt underneath the canister you can loosen to release the canister:

After a few turns, the canister will come loose and you can lift it slightly and pop it out.
Do not yank on the canister: The large vent hose is attached to the top of it and you do not want to rip it.
It runs up into the fender to the vent valve, and would be a pain to replace.
Gently turn the canister sideways and you can see the two J hoses that could be the problem.
You can remove the canister bracket as well with a 14mm bolt (I believe) if you need more room to work.

My J-hoses were not leaking, but I replaced them anyway and continued with the diagnosis.
Do not mix these hoses up. The top of the canister is labeled "purge" and "tank", but you cannot see this from the bottom.
Just disconnect only one hose at a time and you should be fine.

Both tank and purge hoses should hold pressure with the vehicle OFF.
I disconnected the "tank" side J-hose from the top of the canister to see if this section would hold pressure.
I tried to pressurize the tank hose, but it did not hold pressure at all, and I could blow right through it. Problem found!

NOTES:
The tank hose also connects to the gas filler tube. If your gas cap is leaking, this hose will leak through it.
Use light air pressure on the tank side. The fuel pressure regulator is connected to this hose,
and you do not want to damage the diaphragm of the fuel pressure regulator.

If the tank side holds pressure, reconnect it and repeat this with the purge side hose to see if that is sealed.
If it is not, you either have a leaking Purge Valve, or a leak somewhere in the hose that connects to the purge valve.
If they both hold pressure, you most likely have a problem with the vent valve or the hose attached to it. (big PITA)

Moving on, the tank side hose is a long plastic hose that is connected at either end with rubber connectors.
These are what fail.
Since the tank side was my problem, I followed the plastic hose all the way back to the rear passenger wheel,
where it disappears above the fuel filter: (Note the location of the Rollover valve bracket)

I thought this was one continuous hose from the canister to the tank, but it is not. (this is why it took me so long to find)
The rollover valve is hiding above the fuel filter, and there lied my problem.

One of the rubber connectors had become very deteriorated, and snapped off when I barely pulled on the plastic line.
You can remove the bracket that holds the rollover valve by removing a single 12mm Bolt from underneath.
(Refer back to the "side view" picture)

This is the view with the bracket removed:

The fuel filter bracket will come off with one bolt also, but I was able to make the repair without removing it.
I replaced the connector with rubber fuel hose, which I think will not deteriorate as fast as regular vacuum hose.
Here is the repaired hose:

Once I replaced this, I attempted to pressurize the tank side line again. This time it held pressure!
I cleared my CEL and I am now testing the vehicle.
I will update if the code comes back before my drive cycle is completed.

[jreed]

Great write-up! Nice diagnosis and excellent repair! Thanks for posting this.
I had a similar problem a while back and posted a description of it -- it's not as good as yours! Fuel Odor And Broken Hose Near Fuel Filter

[xtrattitude4u]

Ah, I missed that one.
I forgot to mention that I was smelling gas in the cabin after filling the tank.
Your post reminded me to include that symptom in my post. Just edited.
Thanks for the props! Maybe I'll get my 2.5 stars lol.

[xHeart]

A relevant post to my quest for notorious EVAP code P0455.
I will try suggested steps.
Two questions:
1. What is your procedure for checking pressure, would Mityvac have a use here?
2. How long is fuel hose, what is ID and OD?

[cn90]

Thanks for the wonderful DIY.

I currently have code P0440, I keep an OBD-II code reader in the glovebox. When the CEL light is on, I check and it is always P0440, then I erase it LOL.

Seriously, I am waiting for warmer weather to chase this goofy P0440 code.

Thanks again, this will be a good guide for me to follow!

[cn90]

...Once I replaced this, I attempted to pressurize the tank side line again. This time it held pressure!
I cleared my CEL and I am now testing the vehicle.
I will update if the code comes back before my drive cycle is completed.

This thread talks about the same hose too:

http://volvospeed.com/vs_forum/topic/13 ... some-help/

[xtrattitude4u]

What is your procedure for checking pressure, would Mityvac have a use here?

I just cleaned off the end of the hose and blew into it. The purge side is rather short, so it should resist airflow firmly.
The tank side allowed itself to be pressurized a little, but then expelled air back out. (after I fixed the leak)
This is the gas tank expanding slightly, then contracting.

How long is fuel hose, what is ID and OD?

The rubber fuel hose I used to replace the fitting was only 3 inches long or so, about 5mm id and 10mm od.
The plastic hose is about 6mm id and 8mm od. My best guess on the length would be 10 feet or so.

[xHeart]

What is your procedure for checking pressure, would Mityvac have a use here?

I just cleaned off the end of the hose and blew into it. The purge side is rather short, so it should resist airflow firmly.
The tank side allowed itself to be pressurized a little, but then expelled air back out. (after I fixed the leak)
This is the gas tank expanding slightly, then contracting.

How long is fuel hose, what is ID and OD?

The rubber fuel hose I used to replace the fitting was only 3 inches long or so, about 5mm id and 10mm od.
The plastic hose is about 6mm id and 8mm od. My best guess on the length would be 10 feet or so.

I found following three part numbers associated with your repair. The Volvo prices are reasonable.
Would you add any other item to this list?
Coupling piece at the canister for tube to purge valve PN9135831 - $6.07
Tube PN946234 - 1000mm long to rollover valve - $8.81
Coupling at the canister for the above tube PN9141209 - $3.17

Many thanks.

[cn90]

Quick note to say thanks to "xtrattitude4u" for this wonderful guide.

I have had this nagging P0440 code for months, each time I simply reset the code.
Today while replacing the rear shock, I smelled a vague gasoline fume, looked up and see cracked hose at "roll-over valve" as mentioned above.

A few comments:

- When trouble-shooting EVAP codes, always start with visual inspection of gas cap seal, any obvious hose cracks (dry rot with time). This will reduce the amount of time chasing these EVAP codes. Very often, the culprit is cracked hose(s).

- For the roll-over valve hose:
* No need to remove the bracket.
* Use a pair of needle-nose pliers to TWIST the hose to undo the bond between the hose and its connections. Then remove it.
* I happened to have standard 1/4" heater hose laying around. It fits the "roll-over" valve nipple perfectly, but is a tad too small form the other end. No problem, simply enlarge the other hose's end a bit using a pair of needle-nose pliers.
* Add one drop of oil to each end to ease insertion.

Voila, no more P0440 code!.

PS: Wear googles when working under car!.

EVAP01.JPG (93.33 KiB) Viewed 4387 times

[xtrattitude4u]

You can replace the rollover hose without removing the bracket as stated by CN90.
I found it necessary to remove it because I did this repair without lifting the car at all, and it was a tight fit under there.
I don't have a garage right now, and I wasn't waiting any longer to fix this stupid thing!

As for the hose:
I suggest using fuel hose because this connector is constantly subjected to fuel vapor, and is probably the reason it fails.
I assume fuel hose would hold up better than anything else in that application.
I had replaced most of the EVAP system looking for this leak, so I don't ever want to deal with it again!

And yes, wear Goggles. I didn't and got crap in my eyes more than once doing this.