开云体育To recap: Some of us experience the following symptoms: - when it's very hot out (like 95F or higher) - driving at a medium speed (20-40 mph) - up a steep hill - arriving at a high altitude (5000' - 7000' )? Positive symptoms: - strong raw gas smell (around the gas tank area, not from the engine compartment or tailpipe) - gas tank literally sounds/feels like it's boiling - pressure in gas tank (relieved if you open the gas cap) Negative symptoms: - typically no CEL or codes via VCDS - van otherwise drives just fine - once the van cools down, starting and driving at altitude is normal Background: - reports are more common with the 1997-2000 Eurovans vs. the 2001-2003 Eurovans (which have a redesigned Evap system) - this problem seems new - several of us who drive the same routes each year began to notice it 5-10 years ago. - some people report that it gets better with parts replacement (typically N80) - however, many of us have R&R many parts (Evap canister, N80 valve, gas cap, Oxygen sensors...) with no improvement. Design flaw? The Eurovan's gas tank is right behind the engine, and with the right combination of factors (speed, temperature, altitude) you can get in a situation where tons of hot air are coming off the engine and radiator, blowing right by the gas tank, causing the gasoline to boil. ?Even if the N80 and evap system are working properly, gas fumes are created faster than the engine can burn them, eventually overloading the evap system leading to pressure release of gasoline fumes. ? ?An argument consistent with this is that the 2001 and later models have a beefier evap system, seem to be less likely to have this problem, suggesting that VW may have indeed fixed this flaw. The main argument against this theory is that many of us feel like this is a new?problem that didn't happen when the van was younger, suggesting that something changed. Malfunction? If something has changed, it's most logical to think something has worn out or broken in our vans. ?E.g., if the evap system were working better, the problem would go away. ?? The main argument against this theory is that several of us have R&R multiple parts and never found a cure. Could it be the Gasoline? Perhaps something else has changed? ? If the fundamental problem is gasoline boiling in the gas tank, perhaps gasoline formulations have changed to increase the vapor pressure?? In fact, around 2003 California phased out MBTE and started using about 5% Ethanol, and around 2010 rules changed to allow up to 10% ethanol in California fuel blends. ?? It so happens that E10 gasoline is allowed to have a Reid Vapor Pressure (RVP) up to 1 psi higher:? |
