98 v70 NA P0455 - my most loyal friend

[98v70dad]

Later models ( maybe my ME7 car?) have a pressure pump which works on the tank and tests it for integrity. The earlier cars use the purge valve and close the cutoff valve to put vacuum on the tank then test to see how fast it comes back up to atmosphere. If the system does not behave your friend P 0455 is set.

Thanks abscate. I understand how the system works. I've already replaced the shut off valve and the purge valve on my my car and I know where they are. On my car they are up front close to the evap canister which is also up front. In fact, I've replaced everything in the system up front. That's every hose, every valve, the inline filter just before the purge valve ...everything except maybe the check valve between the evap canister and the filter. I'm not absolutely sure my car has one of those...I'll need to check.

I'm now focusing on whats in the back by the fuel tank. I believe the rollover valve just sits open all of the time unless you roll over the car so unless the rollover valve housing or either of the nipples is cracked it couldn't contribute to the problem becuase it doesn't do anything except during a rollover accident.

I'm interested in knowing more about the tank pressure sensor and whether or not you could expose it to liquid fuel by overfilling the tank. I suspect that would not be good and could fail the sensor, especially with gasahol. I'm still hoping that some people knowldgable about that sensor will tell me what they know. If its not that sensor that get damaged by over filling what does?

[cn90]

- For filling up gasoline tank: I always stop about 1 gallon short. So if I am at 1/4 tank, and I know I need 14G to the top, then I fill only 13G to avoid overfill. No matter what I own.

- Re EVAP codes: diagnosing EVAP leak can be difficult/frustrating, specialized shops have smoke machine, I don't.

- When the weather gets warmer I will test a new ghetto technique.
---> I have an air compressor, so will get air to about 10 psi (run the air compressor for 5-10 sec or so), then unhook the hose leading to the EVAP purge valve, hook up the air compressor to the hose. Now the whole system is pressurized to 10 psi or so. You don't want more than 15 psi b/c you may burst some hose connections.
---> Any air leak will create a hissing noise. So you want all noise off (radio off etc.), ideally inside a closed garage, this way you can detect the hissing noise.

Stay tuned.

[erikv11]

I also don't know details about the tank pressure sensor, maybe someone who does will chime in.

But on the rollover valve, I have opened one up I can confirm that your interpretation is correct. It is a simple mechanical device that is open unless you turn it over.

[abscate]

Its a piezo electric sensor - here is a chart of output on my 1999. There are obvious fail points on the hose going to it.

Alldata reports my 1999 has the leak detection pump like the P2 cars - I think this was first year and the <1999 use a combination of vacuum and purge valve to test.

Screen Shot 2016-01-07 at 12.06.48 PM.png (33.37 KiB) Viewed 1647 times

[98v70dad]

- For filling up gasoline tank: I always stop about 1 gallon short. So if I am at 1/4 tank, and I know I need 14G to the top, then I fill only 13G to avoid overfill. No matter what I own.

- Re EVAP codes: diagnosing EVAP leak can be difficult/frustrating, specialized shops have smoke machine, I don't.

- When the weather gets warmer I will test a new ghetto technique.
---> I have an air compressor, so will get air to about 10 psi (run the air compressor for 5-10 sec or so), then unhook the hose leading to the EVAP purge valve, hook up the air compressor to the hose. Now the whole system is pressurized to 10 psi or so. You don't want more than 15 psi b/c you may burst some hose connections.
---> Any air leak will create a hissing noise. So you want all noise off (radio off etc.), ideally inside a closed garage, this way you can detect the hissing noise.

Stay tuned.

I've thought about doing that also. Easy to accomplish, but I am a little concerned about not finding the leak and making it worse in the process. OR causing a leak where I don't already have one.

[erikv11]

Agreed, to do that with you must have a confirmed regulator on the compressor, you want to be certain about the PSI. Or use something like a bicycle pump instead, if you want to roll the dice.

[Thunderbox]

abscate - thanks for the reference pic. Any idea where it is on yours? I think I have something similar next to my charcoal canister and fuel filter in the right rear before the wheel.

[cn90]

Re air compressor, I have the regulator, also have the gauge on the compressor itself.
Also, 5 psi is very safe for many of these parts.

For comparison purpose, a human being blowing a hose is pushing about 1 to 1.5 psi.

[erikv11]

Ah well that makes much more sense cn90. In your post where you proposed ti just "run the compressor for 5-10 seconds" which is not recommended. You would want to establish good pressure in the tank, turn off the compressor, and then adjust the output to the desired pressure with the regulator. Sounds like you are all set.

And now you are talking about even lower pressure, only 5 psi, instead of the 10 psi you originally posted about, even safer. Let us know if you try it, sounds like a good plan. Staying tuned.

[98v70dad]

So today I replaced the tapered vent hose that requires drilling a hole in the trunk area sheetmetal. OnIy on my car I had to drill two holes. Apparently my aim is not that good. Anyhow, I had high hopes since the large end of the tube was loose. I was able to spin the hose clamp easily. I figured that this is it! But as usual my dear friend P0455 is back. I'm not quite sure what to do next. So far I've done the following.

replaced entire PCV system in the engine compartment. Including all rubber tubes off the evap canister, purge valve and shut off valve. All parts were purchased at the dealership or per recommendations here for the PCV upgrade.

Replaced both rubber tubes on either side of the rollover valve. Replaced the 90 degree elbow between the line to the evap canister and the fuel pressure regulator. Replaced the gas cap with a volvo OEM gas cap. Today I replaced the tapered vent tube between the gas tank and "gooseneck".

NO JOY, NO JOY, NO JOY. Whats left? I mean really whats left? Right now I'm frustrated beyond belief.