100 Caught fire & gas tank venting concerns

[jerryb]

that whole thing is kind of spooky, think about the little screws on the fuel pump cover, you think the smell someone mentioned earlier in the thread was a bad seal on the pump cover? I can imagine a failure there spraying vapor or liquid into the seat area.

The vented/bad cap CEL that happens goes away by itself with a new cap, I don't remember how long it takes, probably a two trip counter.

I put a new fuel pump in and it hasn't happened since. It happened to me at sea level 3/4 tank stop and go at 100 degrees or so.
I think there is something to be said about all the 10 plus year old fuel pumps, volume returned to the tank, even if the rail pressure is in spec it still might not have the same volume or flow rate. Not saying a new pump solves it, just that it's part of the picture, just like the fuel pressure regulator/relief valve, canister, etc.

There's no check valve on the return line as it enters the tank either. So that's probably getting back pressurized.
Just my thoughts.

Sitting in traffic on 140 degree asphalt wont help either. I think 87 pump gas will start vaporising at 140 something. I can't remeber, lots of variables.

 

[LostAfrican]

Good stuff here, as is your post on the charcoal canister service.

This is partially helpful, but I wonder if the FSM has some descriptions of how the purge is activated, and how the air inlet and air drain hose work, and how the vapor pressure sensor works? I asked in your other post if you could see how the charcoal had been damaged by the liquid fuel getting up there?

I couldn't tell a difference by just looking at the charcoal. My understanding is that the charcoal works by using its massive surface area (its very porous) and the fact that its carbon to bind with stuff that travels through it. Its like a big sponge. Its purpose is to absorb the ordor when the evap system is venting. If the only problem was the damage to the carbon itself (getting gummed up with too many impurities) we'd be ok, because the system would still vent. The issue is that the vent passage gets blocked, either by liquid fuel, or the valves getting stuck/blocked.

I have not found a nice explanation in the FSM about how its supposed to work. I can infer some stuff from the diagrams, and the methods to test it.

 

[MattThompson]

Speaking of insurance ... how many of us are truly covered to the real value of our rigs if it were to be 100% destroyed?

Most insurance coverage w/o riders won’t cover all the accessory mods many of us have done to our rigs.

Sorry for the hyjack ... should be a thread of its own.

Good time to bring that up! I'm an independent Ins Broker, and have been i the industry for almost 10 years. I would advise everyone to contact their carrier/agent and ask about agreed value coverage. Many carriers do offer coverage for special vehicles (not just classics) and will allow coverage for aftermarket equipment. It costs a little more, (sometimes not much at all) but its important for the enthusiast crowd to know this does exist. Even if you choose not to go that route, it doesn't hurt to ask.

 

[MattThompson]

I have noticed that when I fill my tank over a certain level there is a fuel smell inside the truck for a brief period. Sometimes the hissing sound when I take off my cap is louder and longer than what feels normal and vapor is briefly noticeable. I have never had this happen on another vehicle. My 100 is a 1999 and I live in Oklahoma City, so not a high altitude, but we do see temps over 100 a lot during the summer months. I only run ethanol free fuel, so that isn't a contributor in my case, but could these symptoms mean I need to have my fuel system looked at? If it happens at my current elevation, will it be even worse when I drive to Colorado or NM? My apologies if this has been covered, I'm a bit tired and may have missed it in the thread.

 

[Julian Stead]

that whole thing is kind of spooky, think about the little screws on the fuel pump cover, you think the smell someone mentioned earlier in the thread was a bad seal on the pump cover? I can imagine a failure there spraying vapor or liquid into the seat area.

The vented/bad cap CEL that happens goes away by itself with a new cap, I don't remember how long it takes, probably a two trip counter.

I put a new fuel pump in and it hasn't happened since. It happened to me at sea level 3/4 tank stop and go at 100 degrees or so.
I think there is something to be said about all the 10 plus year old fuel pumps, volume returned to the tank, even if the rail pressure is in spec it still might not have the same volume or flow rate. Not saying a new pump solves it, just that it's part of the picture, just like the fuel pressure regulator/relief valve, canister, etc.

There's no check valve on the return line as it enters the tank either. So that's probably getting back pressurized.
Just my thoughts.

Sitting in traffic on 140 degree asphalt wont help either. I think 87 pump gas will start vaporising at 140 something. I can't remeber, lots of variables.

Maybe your old pump was worn and generating heat in the fuel tank warming the fuel up. Just a thought.

 

[Live to Ski]

Pressure issue happened to me @ somewhere close to 5,687 feet (coming from sea level w. full tank and fairly hot temperature).

Having been ignorant of the winter/summer socal fuel blend rational, it all makes sense now. Summer blends need lower boil-off state to reduce smog vapors in hotter summer temps. think 20 million cars.

 

[PabloCruise]

Summer blends would need a higher boiling point.

 

[Live to Ski]

Correction noted. Just like air pressure numbers....just like metric gravity numbers.....all can be/are confusing.

 

[1meancruiser]

Just an update...i spent my sunday at Frazier Park, CA. around 5500 elevation. I filled up to the rim just before the trail, and the trail consisted of heavy inclines and declines at times over 45°. Temperature was around 50°. it's the first time I've been offroading since I changed the fuel pump, charcoal canister and tank vent. at the end of the trail and again upon return I checked the tank to see if there was any hissing or overpressurization, there was nothing. The last time i had the hissing and fuel boiling issue was at Frazier Park but the temperature was 100°.

 

[morganism]

This could still be a busted fuel pressure regulator leaking onto the block in the front of the vehicle, and the venting just allowed it to spread to the whole area. Those FPR's are a known hazard.

 

[2001LC]

Anyone see a relationship to mods like say a snorkel, or maybe removal of engine cover which has a clip to holds fuel return line?
Just thinking out loud.

 

[Skidoo]

More data on this issue. Ethanol smoking gun?? I just spent a week in Silverton, CO running the high passes. Last year a week earlier I was in Silverton for 100s in the Hills. Weather conditions were the same as last year, and ran the same trails this year. This area has to be the worst case scenario for gas tank venting as Silverton is 9300 feet in elevation and you are going up to passes as high as 13,113 feet from there.

Last year I ran gas with ethanol and had high pressure venting when opening cap at the passes. Only filling to ¾ of a tank helped but did not eliminate the pressure venting. This issue seemed to be common with the other rigs on the trail.

This year 100s in the Hills was too early for me to attend, so planned my own trip with a friend and his 80 series. This year we found a small station in town that offered ethanol free premium gas and we used only that for both our rigs. I had no venting pressure at all when opening gas cap on the high passes this year. After the second day I was filling the tank to full and no issues. My 100 is the same, no changes since last year. My friend’s 80 has had the venting issue in the past but running ethanol free gas here he also had no venting pressure when opening gas cap on high passes.

My belief is that its the ethanol based fuels causing this issue, but run your own tests, see what you find.

 

[bamabrock]

More data on this issue. Ethanol smoking gun?? I just spent a week in Silverton, CO running the high passes. Last year a week earlier I was in Silverton for 100s in the Hills. Weather conditions were the same as last year, and ran the same trails this year. This area has to be the worst case scenario for gas tank venting as Silverton is 9300 feet in elevation and you are going up to passes as high as 13,113 feet from there.

Last year I ran gas with ethanol and had high pressure venting when opening cap at the passes. Only filling to ¾ of a tank helped but did not eliminate the pressure venting. This issue seemed to be common with the other rigs on the trail.

This year 100s in the Hills was too early for me to attend, so planned my own trip with a friend and his 80 series. This year we found a small station in town that offered ethanol free premium gas and we used only that for both our rigs. I had no venting pressure at all when opening gas cap on the high passes this year. After the second day I was filling the tank to full and no issues. My 100 is the same, no changes since last year. My friend’s 80 has had the venting issue in the past but running ethanol free gas here he also had no venting pressure when opening gas cap on high passes.

My belief is that its the ethanol based fuels causing this issue, but run your own tests, see what you find.

I never thought about the ethanol being the issue. Good info.

BTW, we looked for you at HIH this year!

 

[collk22]

More data on this issue. Ethanol smoking gun?? I just spent a week in Silverton, CO running the high passes. Last year a week earlier I was in Silverton for 100s in the Hills. Weather conditions were the same as last year, and ran the same trails this year. This area has to be the worst case scenario for gas tank venting as Silverton is 9300 feet in elevation and you are going up to passes as high as 13,113 feet from there.

Last year I ran gas with ethanol and had high pressure venting when opening cap at the passes. Only filling to ¾ of a tank helped but did not eliminate the pressure venting. This issue seemed to be common with the other rigs on the trail.

This year 100s in the Hills was too early for me to attend, so planned my own trip with a friend and his 80 series. This year we found a small station in town that offered ethanol free premium gas and we used only that for both our rigs. I had no venting pressure at all when opening gas cap on the high passes this year. After the second day I was filling the tank to full and no issues. My 100 is the same, no changes since last year. My friend’s 80 has had the venting issue in the past but running ethanol free gas here he also had no venting pressure when opening gas cap on high passes.

My belief is that its the ethanol based fuels causing this issue, but run your own tests, see what you find.

I didn't have any issues at HIH this year; of course, I generally left my truck running unless it was clear we'd be stopping for >20 minutes.

 

[geanes]

I didn't have any issues at HIH this year as well. Last year, I boiled on both Mosquito and Imogene. I changed the fuel filter and gas cap before HIH8 and had no boil on Imogene, Engineer or later at the top of Argentine Pass (13,280).

 

[abuck99]

Ethanol definitely lowers the boiling point of fuel; but at HIH8 this year I used Ethanol blended fuel and didn't have any issues with pressurization excessive venting pressure etc. and I did have some pressurization venting issues last year.

This year I kept my tank at no more than 1/2 full to start my day, and I also left my truck running most of the time when we stopped at altitude. I have a hunch that leaving the truck running keeps the EVAP solenoids active and allows the EVAP system to continue to cycle. Shutting the vehicle off and you close the loop.

 

[Skidoo]

Did not leave truck running as I stopped to take photos, etc - about same as last year. Did run tank full after 2nd day (since there was no pressure) as opposed to 3/4 or less last year.
What we found telling, on the 80 and my 100 when opening gas cap on high passes, there was no pressure released, none. Had high pressure releases last year. Temperatures were about the same, think a little warmer this year.
Bummed I could not make HIH this year, met a lot of great folks last year.

 

[spressomon]

^ Maybe related to aux tank...but I've never not experienced vapor pressure release when opening fuel filler cap; any ambient temps, any elevation, hot/cold engine, etc.

 

[Bismarck]

FWIW, same thing (less the fire part) happened to me as well, at about 10,000 ft in elevation... lots of fuel smell outside. I made the mistake of opening the gas cap slightly (in my mind to relieve pressure) and ended up with vapor and liquid fuel pissing all over the side of the truck. The tank was probably 3/4 full, new fuel filter and all that.

 

[J1000]

I think there are probably two different phenomena happening at once that are being conflated.

#1 high pressure build up in fuel tank. The evap system is controlled by the ECU and designed to lower emissions and all that good stuff. But it only runs when the ECU tells it to. So cruising on the highway or around town all is good. Even driving to high elevations on paved roads could be fine, but when hitting the trail idling at low RPMs and low speeds, perhaps the ECU just doesn't have many open "evap windows" to use which leads to a build up of pressure.

#2, fuel boiling in tank. Clearly this is not due to over-pressure inside the tank as above, because higher pressure would keep the fuel from boiling until a much higher temperature. To me, boiling fuel is likely caused by the same situation as above, low speed driving for hours on end. As has been pointed out earlier in this thread, the fuel system pumps from the fuel tank to the fuel injectors, and then excess fuel is returned to the fuel tank. As the fuel comes through the injector rail it will heat up from the engine temperature and then return to the tank warmer than it started. Keep this cycle up for a couple hours and now you have heated up your entire fuel tank because at low RPM more fuel is being returned to the tank than is actually being burned in the engine. Increasing your altitude will lower the boiling point of course which is why we don't see this in stop-n-go traffic. Perhaps a heatsink on the return fuel line may help. I also don't know if there is exhaust or coolant hoses that may be running close to fuel lines or the fuel tank.

Yes, ethanol creates more fumes so I would expect scenario #1 to be worse with ethanol fuel, but still could happen with 100% gasoline.