P0450 and lots of pressure when removing the gas cap - on the road in Utah

[nckwltn]

I'm on the road in Utah. Filled up in Vegas several hours ago. Temps have been 100+ the whole day.

At some point I had a pending CEL come on picked up by my ultra gauge of p0450. Everything else was normal. The full CEL never was thrown.

Now just outside of St George, I'm filling up and my gas take has a crazy amount of positive pressure inside that is released by opening the gas cap. It was enough pressure I could feel it rush by my hand.

I'm going to idle for a few mins and see if any pressure builds up.


Any ideas? Thanks!


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[nckwltn]

Idling for 5mins and no pressure. Will check it again in a few miles.


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[nckwltn]

20 miles down the road. Just a normal amount of pressure build up.

Strange. I did notice at my last check that the gas cap did seem to start clicking early, and a few more twists and the cap when on tighter.



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[digitaldelay]

http://engine-codes.com/p0450_mitsubishi.html

I'm trying to figure out if the high temp and resulting tank pressure is causing the EVAP system to malfunction and not purge into the intake, or if high tank pressure is normal in hot weather and you simply have a sensor malfunction.

Jason

 

[nckwltn]

A few more miles down the road and some elevation change and it is happening. This time with a near full tank gas is sputtering out with the cap fully removed.


I'll probably try going for a bit with a loose cap just to keep pressure from getting too high.


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[nckwltn]

And. I have no pending codes. Car thinks it is running just fine


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[jeep-N-montero]

It's pretty "normal" for Utah in the summer, heat+drastic elevation changes result in a bit more pressure.

 

[nckwltn]

I've got a copy of the fsm with me I'll be digging into after dinner. The about of pressure was pretty crazy. To the point of air rushing out for several seconds after fully removing the cap.


The pending code is what had my spicy senses on edge. The code never fully hit. But something was happening.


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[Fergie]

You may be overthinking this and trying to correlate to unrelated things.

In summer heat, especially when filling a near empty tank, there is always a lot of pressure release.

Unless you are having driving issues, I'd monitor the situation, but not brain hump it.

Depending on the direction you are heading, my driveway and possibly a garage are open in Flagstaff, AZ, if there is a serious issue that arises.

 

[nckwltn]

Depending on the direction you are heading, my driveway and possibly a garage are open in Flagstaff, AZ, if there is a serious issue that arises.

thanks and appreciate it. I did bring some tools along, seems like unless you're getting into the drive train, 10, 12, 14, 17mm you can do anything on these cars. We won't be going back through that direction until later next week on our return to LA.... and even then, we don't have a route set. Tonight we are in Escalante UT, we had a late start yesterday and only made it to Vegas... wife was not happy with the 95+ temps at midnight in our pop-up trailer. I'll need to plan higher elevations for cooler nights if I ever want my wife to go again.

the crazy part about one of the times is that it was 20 miles after I filled up.... so the near full tank of liquid shouldn't have been that compressible, meaning that there shouldn't have been room for a pressure build up. I can see how when we arrived in St George with less than half a tank, that does leave a lot of room for the vapors to compress.


I'll try to capture something on video over the next few days to see what happens.... I assume there is some kind of pressure relief valve on the gas tank, so that pressure can never build up beyond what the tank can support (like a hot water heater).


time to research P0450

Does the Gen 2.5 have a return line to the tank for extra fuel that isn't used?

 

[jeep-N-montero]

Hot summer nights are pretty much the norm for southern Utah, we just spent 3 nights in the northern mountains and it was nice with days in the 70's and nights in the 40-50 range, we were dreading coming home as we watched the thermometer in the Montero climb from 68 when we left our campsite to 93 in our driveway.

 

[nckwltn]

Up at the near opposite corner from St George tonight. Might have to use a blanket.

Whatever the problem was, it never came back. That was the strangest thing.

The pending code alarm didn't come back on either.


The only problem I'm having now is the lack of power at these higher elevations. Pulling a very small pop up camper trailer and keeping speed is impossible.


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[jeep-N-montero]

Up at the near opposite corner from St George tonight. Might have to use a blanket.

Whatever the problem was, it never came back. That was the strangest thing.

The pending code alarm didn't come back on either.


The only problem I'm having now is the lack of power at these higher elevations. Pulling a very small pop up camper trailer and keeping speed is impossible.


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Ha ha, welcome to my world, this is why I will be running the 4.93 gears soon to help combat power loss at upper elevations. Are you northeast of Logan or closer to Evanston?

 

[nckwltn]

Ha ha, welcome to my world, this is why I will be running the 4.93 gears soon to help combat power loss at upper elevations. Are you northeast of Logan or closer to Evanston?

oh hey, you're in Utah too! I'm in Vernal... this is about where I wanted to be at the end of Day 2 and not the end of day 3... but day 1 didn't start with 9am on the road... it started with 4pm on the road. I sure am glad I went with at least the 4.63 gears I can't imagine this on 33s with the 4.27 gears!

But it has been cool to see all of the dramatic scenery the state has to offer.. we came over through Zion, stayed in Escalante last night, and puttered east on 12 back a little on 24 at Torry and then north on something else up to Price.

It was crazy in some of those smaller towns north of 70 but before Price... on a sunday afternoon at 2pm, it looked like the towns were abandoned or like it was Christmas morning. there was NO ONE out.

 

[jeep-N-montero]

oh hey, you're in Utah too! I'm in Vernal... this is about where I wanted to be at the end of Day 2 and not the end of day 3... but day 1 didn't start with 9am on the road... it started with 4pm on the road. I sure am glad I went with at least the 4.63 gears I can't imagine this on 33s with the 4.27 gears!

But it has been cool to see all of the dramatic scenery the state has to offer.. we came over through Zion, stayed in Escalante last night, and puttered east on 12 back a little on 24 at Torry and then north on something else up to Price.

It was crazy in some of those smaller towns north of 70 but before Price... on a sunday afternoon at 2pm, it looked like the towns were abandoned or like it was Christmas morning. there was NO ONE out.

Yeah, Sundays are really quiet in Utah, most folks are in church or inside out of the heat.