EVAP leak whack-a-mole

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Been hunting the cause of a persistent check engine light for a while. Finally got serious when the P0442 code for small evap system leak was joined by a P0455 large evap leak code that would appear within a day of getting cleared. Also noticed a whiff of fuel vapors from rear of car once in a while. Took off inspection covers for fuel pump area and the smell almost knocked me flat. Fuel pump assembly was leaking badly, to the point of leaving a small puddle of fuel on top of the tank. Since i could not unscrew the unit, I tried a last ditch effort and used fuel-resistant gasket maker to seal around the edges. Messy, but very cheap and effective (first image). P0455 and fuel smell went away, but the P0442 code stubbornly remained.

I built a smoke generator to aid in visualizing the leak. Soldering iron, inlet port, and outlet port attached to the lid of a glass jar with epoxy. A bundle of paper towels as a wick wrapped around the iron and extending to a pool of mineral oil at the bottom of the jar. I used a low power aquarium pump since it has a very low max pressure. (second image).

I unhooked the vent line to the fuel tank and plugged in the smoke generator. After a few minutes, I began to see very faint wisps of smoke near the fuel pump assembly, but a soaking of soapy water yielded no bubbles. The fuel sender is a separate unit right nearby, so I sprayed the soap there, and was rewarded by a stream of bubbles. Another application of the gasket maker and both bubbles and smoke stopped (third image). I thought I was done, so I cleared the codes and drove as normal for a while.

Alas, the P0442 just returned. Tomorrow the smoke machine comes out to play again, and I hope its a part I can replace or a crack I can plug with goop. I feel like I'm playing whack-a-mole here
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Does your Volvo have the leak detection pump and J hose like later models? The LDP is very sensitive, and the J hose often gets a crack...
 
Don't think it has the same j hose as shown in all of the instructions online. Charcoal canister lives up under left front fender instead of right side near the fuel filter and rear wheel.

There is a small pump mounted under battery tray near the canister so that may be the LDP.

Feels likes the system developed more holes than Swiss cheese.
 
Decided to take a peek under the left front fender at the charcoal canister area. Removed wheel and fender liner and was greeted by a hose with a split right at the purge valve. Also noticed there was a (loose) ziptie instead of a hose clamp at the canister.

Replaced offending hose with 8mm ID silicone hose I had left over from when I redid the underhood vacuum lines. Used spring clamps at both ends. Cleared codes and will report back if the repair solves the P0442.

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I see silicone not recommended for fuel or oil. Think fuel vapor is okay?
 
Originally Posted by spackard
I see silicone not recommended for fuel or oil. Think fuel vapor is okay?


EDIT: Misinterpreted your statement. I'm assuming silicone hoses meant for engine e vacuum lines are resistant enough to fuel vapor. Otherwise they wouldn't be much use in engine applications.

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Rtv silicone is not super resistant to gasoline.

I used permatex Motoseal which is a different kind of gasket maker meant for application in contact with fuel such as 2 cycle engine case halves and carburetor gaskets.
 
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UPDATE: Issue is finally resolved after fixing all three of those leaks. Car now passes self tests with no trouble codes for the first time in years.

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