- Thread starter
- #121
Any thoughts on my last thoughts?
Excessive fuel tank pressure
- Thread starter MaddBaggins
- Start date
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Not sure how much this really helps, but I had a *slight* fuel pressure problem on my cruiser. No where near 30 minute venting when the gas cap was taken off, more of a slight gas smell by the cap.
As the first step to try and fix my 401 code, I found that the vacuum passthrough the intake was clogged. IIRC the vacuum/vsv is used by both egr and vapor recovery? Maybe someone can confirm this. Anywho, after unclogging that line the fuel smell has pretty much disappeared from the gas cap area. Have not yet gone through the drive cycle for the 401 code, so there may still be other clogs in the line and its all coincidence.
Corey
- Thread starter
- #125
Just threw a code 71 today. First time I've ever had a code. Code 71 on a 94 is EGR. I guess I'll chase that problem and get it fixed and see next summer if that helps my vapor issue.
- Thread starter
- #126
Cleaned out the EGR modulator and checked all the hoses and that cleared my cel. For now anyway.
my cruiser has started this problem about 5 months ago. My Headgasket has recently blown and after i removed the fuel lines from filter under the intake, fuel was gushing out. When i removed the gas cap it vented for a couple mintues, the fuel stopped flowing obviously from no pressure. For some reason my tank is building pressure when the vehicle is parked and hasnt been running in almost 4 weeks.
I had to replace my EVAP Cannister ... it was clogged.
My '97 has been off the road for 2 weeks waiting on parts.
I replaced the fuel filter while it was sitting. I had the throttle body offf, but just wired up, to keep it out of the way.
Didnt change anything else. Sub tank M/T and 1/4 full main tank.
Put everything back together, and drove 6 miles ,to the same place as I do every other day.
Got pressure,man! Also on the way back, the engine stopped while driving . Sat for a minute, started and drove ok.
No codes.
Mark
I replaced the fuel filter while it was sitting. I had the throttle body offf, but just wired up, to keep it out of the way.
Didnt change anything else. Sub tank M/T and 1/4 full main tank.
Put everything back together, and drove 6 miles ,to the same place as I do every other day.
Got pressure,man! Also on the way back, the engine stopped while driving . Sat for a minute, started and drove ok.
No codes.
Mark
- Thread starter
- #130
Now that it's hot again, I still have the gas smell coming from the drivers side engine bay. I guess I mess around again this summer and see if I can't figure out what the issue is.
Recap:
Evap system is not taking care of fuel vapor during the hot months, especially when I gain altitude.
I live in Tucson 2500'
Typical summer temps 95-115
CC changed out, did not help
All check valves beyond CC test good per FSM
lines to and from tank blow clear with air hose
New fuel pump and sock, tank is clean
Fuel filter is a few years old
Recap:
Evap system is not taking care of fuel vapor during the hot months, especially when I gain altitude.
I live in Tucson 2500'
Typical summer temps 95-115
CC changed out, did not help
All check valves beyond CC test good per FSM
lines to and from tank blow clear with air hose
New fuel pump and sock, tank is clean
Fuel filter is a few years old
- Thread starter
- #132
Smoke test?
I would try a new fuel pressure regulator. I think the fuel may get too hot if there is inadequate flow through the fuel bar. Did you do a fuel pressure test?
I may be way off base here......
Attached a pcture of the tank filler neck (from a bad gas tank)
I may be way off base here......
Attached a pcture of the tank filler neck (from a bad gas tank)
There is a larger-than-usual-diameter vacuum hose that comes off the intake manifold just after the throttle body. If I understand the system correctly, it provides the main vacuum source for the EVAP and EGR systems. You can see the hose in this photo coming off the intake manifold at 5 o'clock and bending around to the plastic T that splits the vacuum to the VCV for EVAP and the VSV for EGR.
Mine looked like this at both ends.
If you have not already, I would replace that hose as it may not be providing enough vacuum for the EVAP system.
Mine looked like this at both ends.
If you have not already, I would replace that hose as it may not be providing enough vacuum for the EVAP system.
Looks like I've run into a similar problem as others on this thread.
We went out today and ran over Mosquito Pass here in Colorado. Stopped at the top (13,134 feet) and I heard hissing coming from the CC. I pulled the gas cap and had some serious venting going on. With that much vapor coming out, it had to be boiling fuel. It wouldn't stop so I eventually put the cap back on and drove on. Coming down the back side of the pass, I checked the cap periodically and it got better as we headed into Leadville at about 10,000 feet. After being on the highway for a few miles, I checked the cap and had vacuum in the tank. Going up another pass in the afternoon that topped out around 12,000 feet, I had pressure again. It was not a clog in my tank line since that line was blowing plenty of vapor when I unhooked it from the CC. I eventually connected the two lines from the CC to each other with a hose barb and that helped the pressure and the fuel smell went away. Again, after I dropped elevation and picked up speed, I believe it cooled the fuel down and brought it below the boiling point. This evening I was back to having a vacuum with my CC properly connected again.
My cooling system is fine, but I believe the high elevation, slow driving and warm temperatures were the problem. Fuel formulation may also play a part since they mix fuel here in Colorado with ethanol. The only "solution" I can come up with is to install a fuel cooler before it goes back into the tank. I believe the fuel is picking up an insane amount of heat in the engine bay and bringing it back to the tank. With higher road speeds, the lines get cooled and the problem goes away.
At least that is my theory at the moment.
Adam
We went out today and ran over Mosquito Pass here in Colorado. Stopped at the top (13,134 feet) and I heard hissing coming from the CC. I pulled the gas cap and had some serious venting going on. With that much vapor coming out, it had to be boiling fuel. It wouldn't stop so I eventually put the cap back on and drove on. Coming down the back side of the pass, I checked the cap periodically and it got better as we headed into Leadville at about 10,000 feet. After being on the highway for a few miles, I checked the cap and had vacuum in the tank. Going up another pass in the afternoon that topped out around 12,000 feet, I had pressure again. It was not a clog in my tank line since that line was blowing plenty of vapor when I unhooked it from the CC. I eventually connected the two lines from the CC to each other with a hose barb and that helped the pressure and the fuel smell went away. Again, after I dropped elevation and picked up speed, I believe it cooled the fuel down and brought it below the boiling point. This evening I was back to having a vacuum with my CC properly connected again.
My cooling system is fine, but I believe the high elevation, slow driving and warm temperatures were the problem. Fuel formulation may also play a part since they mix fuel here in Colorado with ethanol. The only "solution" I can come up with is to install a fuel cooler before it goes back into the tank. I believe the fuel is picking up an insane amount of heat in the engine bay and bringing it back to the tank. With higher road speeds, the lines get cooled and the problem goes away.
At least that is my theory at the moment.
Adam
I did a little more research as follows.
At 13,000 feet water boils at 187 F.
Gasoline, due to the wide variety of hydrocarbons that it is composed of has a boiling temp between 100 and 400 F with the lighter hydrocarbons being the first to boil off.
Ethanol boils around 170 F at altitude.
Therefore, it is entirely plausible that the lighter hydrocarbons in my gasoline were boiling due to superheated return fuel being deposited back into the tank.
Adam
At 13,000 feet water boils at 187 F.
Gasoline, due to the wide variety of hydrocarbons that it is composed of has a boiling temp between 100 and 400 F with the lighter hydrocarbons being the first to boil off.
Ethanol boils around 170 F at altitude.
Therefore, it is entirely plausible that the lighter hydrocarbons in my gasoline were boiling due to superheated return fuel being deposited back into the tank.
Adam
Alright, Whilst we are talking about tanks and fuel, I have had 2 x 80's and 1 x 105 series that if the rear sub tank is more than 1/4 full there is a lot of fuel vapour comming from the rear passenger side (drivers side in the US). There isn't a wet spot of leaking fuel that I can find and one was converted to a dual cab so I could see it easily.
It doesn't matter if the front tank is full or even overfull as I have never heard of the other issues that you guys have.
Has anyone had this problem? did you find a cure?
It doesn't matter if the front tank is full or even overfull as I have never heard of the other issues that you guys have.
Has anyone had this problem? did you find a cure?
- Thread starter
- #140
I have not found a solution. I have narrowed it down to hot fuel being the issue for sure.
I've put 18 gallons (of cool fuel from the underground tank) in at the last gas station before climbing the mountain, then went up the mountain (gaining 6000' in less than an hour) and had no issue.
While I was up there I walked around other vehicles that were parked. There was gas smell coming from many different makes and models, including a newer model Dodge truck.
Definitely a temperature/altitude gain issue. Which, again, is the only time I have this problem.
My next step will be to insulate my fuel lines and exhaust. I've been looking at the fuel return line from the regulator also. It has been speculated that if it was bad it could be heating the gas as well. Next time I call Dan I may just get a new one and see what happens.
Edit: Tucson is above 2000' to start with, if that matters to anyone.
I've put 18 gallons (of cool fuel from the underground tank) in at the last gas station before climbing the mountain, then went up the mountain (gaining 6000' in less than an hour) and had no issue.
While I was up there I walked around other vehicles that were parked. There was gas smell coming from many different makes and models, including a newer model Dodge truck.
Definitely a temperature/altitude gain issue. Which, again, is the only time I have this problem.
My next step will be to insulate my fuel lines and exhaust. I've been looking at the fuel return line from the regulator also. It has been speculated that if it was bad it could be heating the gas as well. Next time I call Dan I may just get a new one and see what happens.
Edit: Tucson is above 2000' to start with, if that matters to anyone.