Beware Of Aftermarket Junk (Evap System)

Post by **packetfire** » 10 Jul 2022, 20:48

In May, I got a few "Loose Gas Cap" warnings from the DIM on my 2004 v70.

The gasket looked worn, so I ordered a new one - not a Volvo part, a 3rd party part.

But the replacement was U-shaped with the closed part of the U against the plastic circumference of the gas cap. The original was a solid round rubber o-ring.

The new part seemed to work fine. But in July, I got an ECM-4308 "Major Fuel Tank System Leak".
I ran the usual VIDA diags, and even pulled the purge valve out to plug the feed from the evap canister, as VIDA suggested, as this proved that the problem was back at the tank end, not the front end.

With the error persistent and a significant leak, I put some silicone caulk on the outer surface of the "new" gasket, and felt stupid about having thrown away the old gasket. Once the caulk had time to cure, VIDA suddenly had nothing to complain about.

So, even something as simple as a rubber o-ring can be substandard for Volvo purposes, and cause leaks so significant, VIDA estimates the size of the leak as anything from "> 4mm" to "> 1mm".

: leak_found.jpg (91.72 KiB) Viewed 824 times

Post by **br0dy519** » 10 Jul 2022, 21:07

Nice post, but where in VIDA does it provide that hose plugging instruction? I feel ashamed to say I've never performed that step in all of my EVAP troubleshooting. Although I have ran the tank test before.

Post by **packetfire** » 16 Jul 2022, 10:43

I am not sure that VIDA specifically suggests it, but it is "common knowledge" appropriate for any EVAP system, as they are all very similar.
There is invariably a "hard line" (not a rubber hose, but metal or very husky plastic) from the canister to the purge valve.

If you look at a diagram of any evap system, you can see that isolating the "front of the car" from the "back of the car" is a simple way to find a leak, so if I can block the line somewhere, (and really do a solid job of "blocking") I can re-run the test, and see if I get the same leak test result as before. I can keep doing this, hose by hose, and find a "leaky valve", without messing with the valves, trying to open or close them with jumpers, etc etc.

This is nothing more than wisdom wrung from experience, and common sense.

Post by **packetfire** » 16 Jul 2022, 10:48

Updated on gasket - if your gasket is U-shaped and has curved arms with some "meat" on them towards the middle, this is a good gasket.

If your gasket is a thin set of flat planar surfaces on each arm of the U, this is NOT a good gasket - this is a bad gasket.

Thanks to a local auto parts store, who ordered "one of each" for me, and got in 4 gaskets, I found the basic design defect in the cheaper variants.

Post by **br0dy519** » 16 Jul 2022, 17:18

some of us are humble enough to admit that we have no common sense or wisdom, but I appreciate your clarification

Post by **kallekula** » 17 Jul 2022, 03:28

You gotta work smarter. As a pro mechanic you’ll wear out fast otherwise. organization is absolute crucial and I wouldn’t be surprised if you crawl roll or run for 50% of your tools. Organize everything and always put the last tool used where it used to be. Not finding tools is extremely annoying, especially if you’re on the clock.

Post by **abscate** » 17 Jul 2022, 04:40

I’ve been slowly conquering tool spray. At the end of a big job when you are tired, it’s hard to get motivated to put everything right but that s the key. At a minimum, I keep all the tools in use in a box, then at the end at least have them gathered in one place.

Somehow , I don’t mind starting the day fresh sorting tools, I kind of enjoy it.

Back on evap. I don’t think the P2 evap test sequence is documented here. I’m pretty sure it’s leak pump driven, rather than vacuum driven

Post by **br0dy519** » 17 Jul 2022, 06:37

From what I can tell, it pressurizes the tank and measures the differential pressure between the tank/evap system and atmosphere.

Post by **abscate** » 17 Jul 2022, 07:42

The pup does four independent tests of the integrity of the whole system and reports back a specific code for each test. If you read the details you quickly figure out the code is guidance only, as any one of many failures can cause a test fault.

First test, for example, is closing off the canister shit off valve and then monitoring tank pressure.

If it fails, it reports canister shut off valve failure. A torn hose in the evap would cause the same fault.

User Lexia got her/his hands on the test protocol for P80mand posted it, we don’t have the same for P2 TTBOMK