gas tank woes (1 Viewer)

[cruiserland]

OK , looking for some idears....
This is the third gas tank i have replaced in my 96 80 in eighteen months. The 3 tanks have gotten holes/cracks in the exact same spot, on the top of the tank near the front. you can see the leak whenn tank is installed; there is no contact here. a crack about an inch long occurs where the tank is molded to accept the parking brke cable routing. The first time I thought I crushed it wheelin, but saw no evidence, replac3d with new tank from Toy, could not find junkyard tank not crushed. the second time I was stumped, thought maybe big stick got jammed wheelin, knew did not highcenter, new tank lasted 6 months, uncrushed junkyard tank with portapower and put it in. less than six months, junkyard tank is leaking. Toy has warranteed new tank with crack. I pull junk tank yesterday to find whole top of tank is crushed in, pump/sending unit tower is bent like 30 degrees. Now i have a new tank, but am hesitant to even start the truck. all tanks have installed easily with stock straps.
THE Question: why is this happening? it seems as if there is some severe suction being created inside the tank. I understand this is a pressurized system.
I have replaced the fuel filter about 4 months ago, not fun. Could i need a new gas cap? Any thoughts?

 

[cruiserdan]

The cap should not allow air out and should allow air in. Have you had the same cap the whole time? Do you live in an area with emissions testing? Test stations may have equipment to test cap function.

 

[cruiserland]

original cap far as i know...150K on truck. sealing surface of filler has minor rust... new cap is only 13 $ i think...no emissions yet in NH, next year. Thinking back, wierd noises were coming from cap in middle of winter at 20 below, shut off truck and would whistle for minute or two....

 

[cruiserdan]

The cap may not be allowing air into the tank resulting in a vacuum.

 

[cruiserland]

OK, it happened again
4th tank with leak in same spot
replaced gas cap with new OEM with last new tank from toyota.

Any thoughts?
air return line( is there one?) to tank is blocked?

 

[RavenTai]

is your charcoal canister in place and hooked up correctly?

a weird problem in the evap system, like misplaced lines could possibly port intake manifold vacuum to the fuel tank causing your symptoms.

 

[Grench]

OK, paranoia setting in. My gas cap sucks air pretty hard when I loosen it to fill the tank.

Where is the canister at?

 

[RavenTai]

mine is usually but not always lightly pressurized, air rush out not in, when not pressurized it is just neutral, never noticed it to have a vacuum. I briefly ran an after market cap provided by the emissions place when my original one failed the test, it generated no pressure at all in either direction.

the charcoal canister is just aft of the battery near the fuse box, it is roughly shaped like a coffee can, there are two lines at the top and a line out the bottom that runs into the frame to vent.

the canister is marked on top, one line runs to the tank, the other to a VSV on the engine,

the vapors that evaporate from the tank are vented through the canister then out the large line at the bottom, the charcoal absorbs the fuel, at certain times wile the engine is running the VSV valve opens drawing fresh air from the line at the bottom up through the charcoal taking the fuel vapors with it and burning them in the engine.


one possible explanation is maybe if that exit line out the bottom were plugged with mud or a mud dober nest (y'all have those in the rest of the country?) instead of drawing in fresh air the engien would draw all the air out of the fuel tank?

maybe take out the charcoal canister and blow though all the lines and make sure they are clear, also make sure the lines are all hooked up to the proper ports, there is a filter in the bottom of the canister, it could possibly be plugged also, so make sure air can flow through the canister itself,

seams like something is either not hooked up right or it is plugged.

 

[Skillet]

Okay, this is bizzaro.

Never have I heard of a tank cracking from pressure like that, much less four of them.

Seems like the car would stop running before that happend.

I have never heard of a leaky 80 series tank, period.

I have the 44 gallon aux tank that dumps into the vent for the stock tank and when I take my fill cap off, I get some serious sucking, but never has anything leaked or cracked.

Sounds like some thing very strange to me.

 

[RavenTai]

although not on an 80 I have seen vent problems cause a tank to collapse as the fuel is pumped out, usually the first indication is that the tank cannot take as much fuel on fill up as it used to, it happens. usually it is the cap, but since he replaced that now looking at evap system.

 

[cruiserland]

thanks for thoughts
did replace cap
third tank replacement revealed the pump tower bent, as if the tank had indeed collapsed somewhat.
will check underside of canister vent, we got mud and wasps
should not take long to empty the tank
at least i have old ones to weld up

 

[RavenTai]

be careful welding on fuel tanks, if proper procedures are not taken it can be deadly. there is no way to fully remove fuel from the pores of the metal tank.

 

[Grench]

Should the charcoal canister be replaced as PM every 10 years or so? Can it even wear out?

 

[GXO]

I know it can be overwhelmed with frequent overfilling.

I had a stinky one once and it was quite contaminated.

 

[RavenTai]

the EPA would probably say yes, but as long as it is not plugged and you are not smelling fuel around the vehicle it is fine, IIRC it is expensive.


honestly it is a piece of environmental emisions equipment that does not make any contribution to the primary function of the vehicle. and if mine were to ever give me troubles I would delete it. only down side might be an occasional wif of fuel wile it was parked in an enclosed space like a garage,

 

[bjowett]

My buddy had to replace the tank on his due to the same leak.

 

[cruiserland]

OK,
finally pulled into shop and yanked charcoal canister. Tube on bottom routes to metal fitting which bolts to frame, thereby drawing air from inside framerail. Well, the metal fitting is rusted solid and will not let any air pass through.
This must be the root of the problem
grench, bjowett, I would recommend pulling this tube and cleaning it out or replacing
Hopefully toyota will give me another tank....
thanks to all for the help

 

[Grench]

OK,
finally pulled into shop and yanked charcoal canister. Tube on bottom routes to metal fitting which bolts to frame, thereby drawing air from inside framerail. Well, the metal fitting is rusted solid and will not let any air pass through.
This must be the root of the problem
grench, bjowett, I would recommend pulling this tube and cleaning it out or replacing
Hopefully toyota will give me another tank....
thanks to all for the help

I established last night that my gas cap doesn't suck. It blows. *rimshot*

I disregarded all instructions printed on the cap and spun it open fast. It flew off with a pleasant foomph.

I'll still be tracing back that line from the canister. Where abouts does it connect to the frame at? I.e. DS X feet back from the front bumper..???

 

[cruiserland]

I'll still be tracing back that line from the canister. Where abouts does it connect to the frame at? I.e. DS X feet back from the front bumper..???

it is just below canister, inside of rail just above vent line for axle, one 12 mm bolt holds it in......

 

[Grench]

Hmmm...

I have been wanting to re-route the breathers anyway. Does anyone see harm in putting this to a T and running it in line with redirected breathers up to near hood level with a mini-filter on it?