New or used spare?
Excessive fuel tank pressure
- Thread starter MaddBaggins
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Spare is new.
The relay swap did not solve the issue. No change. Moab was still fun though 
This is quite an interesting read. I replaced my CC with the Delco part 4 years ago, maybe 10,000miles (I dont drive her much), as I was seeing the pressure release when filling up. Nowhere near as bad as some people on this thread have reported though!
A couple months back I loaded up the 80 and did the WABDR run. The fuel smell was terrible! and on the highway sections my economy dropped as well. I wonder if their are any fuel differences between Canada and the US as I have never had that issue up here.
A couple months back I loaded up the 80 and did the WABDR run. The fuel smell was terrible! and on the highway sections my economy dropped as well. I wonder if their are any fuel differences between Canada and the US as I have never had that issue up here.
Ethanol?
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- #347
I agree whole heartedly. Unfortunately, gas with no ethanol is pretty much unobtanium around here these days. Last I could find, I'd have to blow nearly a half tank to get somewhere that sold non-ethanol.
@MaddBaggins you've done the most work on this. Any method you recommend??
I really think people are discounting exactly how much vapor is being released for how long in this thread. 10 minutes of off gassing is a very significant volume. In order to produce these volumes of vapor a significant heat source has to be boiling the fuel somewhere in the system. The difference in the boiling point of nonethanol gasoline and pure ethanol is only 7 degrees. 87 octane fuel boils at 180F at sea level ethanol at 173F at sea level. I would look for heat sources close to the gas tank to trouble shoot this mainly exhaust gaskets or damaged/missing heat shields.
I found the heat source
If that were the case every vehicle in Arizona would experience these issues every time someone drove to flagstaffI found the heat source
yep
It is just a matter of volume a 30 second off gassing would be the ambient air temperature and a bad CC. 10 minutes of off gassing and liquid fuel being spit out the full neck is a lot more than 120 degree sun.
Saying that gasoline boils at a certain temperature is telling only a small part of the story. The fuel in our trucks is made up of many different components with the lightest of them start boiling off around 100 degrees at atmospheric pressure and going up from there. The hotter you get the heavier the components will start to vapor off. The end point of your typical gasoline is around 400 degrees which means it takes that much heat to boil off all of the heaviest components in there.
If it wasn't so late and I wasn't so tired I would elaborate a bit more. But I run the console (think Homer Simpson) of 2 different units at an oil refinery. One of them is a reformer which takes in heavy naphtha with an octane rating of around 50 or so and bumps it up to anywhere from 85-100 RON, just depends on what the needs are.
Good to know. I was just saying that a tank off gassing for 10 minutes non stop with significant volume and pressure to force liquid fuel out the filler neck was requires a significant amount of heat. More than just a hot summer daySaying that gasoline boils at a certain temperature is telling only a small part of the story. The fuel in our trucks is made up of many different components with the lightest of them start boiling off around 100 degrees at atmospheric pressure and going up from there. The hotter you get the heavier the components will start to vapor off. The end point of your typical gasoline is around 400 degrees which means it takes that much heat to boil off all of the heaviest components in there.
If it wasn't so late and I wasn't so tired I would elaborate a bit more. But I run the console (think Homer Simpson) of 2 different units at an oil refinery. One of them is a reformer which takes in heavy naphtha with an octane rating of around 50 or so and bumps it up to anywhere from 85-100 RON, just depends on what the needs are.
Saying that gasoline boils at a certain temperature is telling only a small part of the story. The fuel in our trucks is made up of many different components with the lightest of them start boiling off around 100 degrees at atmospheric pressure and going up from there. The hotter you get the heavier the components will start to vapor off. The end point of your typical gasoline is around 400 degrees which means it takes that much heat to boil off all of the heaviest components in there.
If it wasn't so late and I wasn't so tired I would elaborate a bit more. But I run the console (think Homer Simpson) of 2 different units at an oil refinery. One of them is a reformer which takes in heavy naphtha with an octane rating of around 50 or so and bumps it up to anywhere from 85-100 RON, just depends on what the needs are.
Are you working on CCR? We have UOP unit that typical to 101-106 RON because the lowest grade of gas in Israel is 95 and we have 98 in all gas station mandatory. No ethanol (some times, some MTBE)
And we have summer and winter blends
Yes indeed, the platforming section has a CCR.
It's a rather old unit now (built in 1984) but it still runs pretty good when we're not burning holes in the regenerator screen! Before the expansion 7 years ago that doubled the refinery throughput to ~650k we would normally run close to 50k BPD and 98-100 RON. But they built a new bigger better version of our unit so now we usually run 26-35k and 90-92 RON. I joke that we're pretty much a utilities unit now, they give us just enough feed to run and and put out that oh so valuable hydrogen for use in the hydroprocessing units and it also makes a good bit of 600# steam from a waste heat boiler. If we didn't make either of those they probably would have shut the unit down years ago.
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- #360
I still have this issue every summer. I've found no resolution. When I drive up the mountain in the summer, I smell gas coming from other vehicles up there. I smell it in town as well. It's always early 90's vehicles that I notice. These vehicles were not designed to deal with this ethanol. It lowers the boiling point of the fuel and the vapors overwhelm the canister. The factory gas cap is set to 4psi IIRC, so the time I had gas blow out of my tank fill port, it was boiling in the tank but was still under 4psi. My mistake was opening it to relieve that pressure. Nothing like a gas shower on a hot day in the desert.