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Fuel tank mystery: Here's what I found inside


Tim_with_the_tj

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Alright, here's what's going on. I've had this 1997 TJ for a few months now. I've never been able to get more than 3/4 tank of fuel into it when filling it. You have to run the pump as slow as possible by hand or it will shut off. Once it gets to around 3/4 full it will not allow you to get any more into it. There is no splash-back problem. It simply won't fill.

Until now, I hadn't been able to fix the issue. I checked the normal stuff like removing the filler neck. It was all clear. The smallest vent line from the tank was disconnected. I reattached it on the frame side. Made no difference.

I came across some videos showing how the spring loaded check valve inside the tank gets frozen up. Today I decided to drop the tank and see what's going on.

Once I got the tank down, I noticed the base of my filler is made differently on the inside of the tank. It does not have plastic clips inside the tank and it cannot be removed. It's also black, not white, and has an orange plastic ball inside with no spring. Hmmm. I searched the bottom of the tank for a spring or something else related to this mechanism. I found no such thing...but I did find this black cap sitting at the bottom of the tank. Wtf.



It says "Blitz" on the top and a google search revealed that Blitz was a large manufacturer of gasoline cans that went out of business back in 2012. Somehow this cap ended up inside my tank. I don't think it was affecting anything, but at this point I was wondering what kind of stuff is really going on here.

In the next video, you can see inside the tank and inside the base of the filler neck. The orange ball was stuck at the top of its cage, so I freed it up. Now the ball moves freely up and down with no resistance. Is this a damn ping pong ball??? At this point nothing would surprise me.

If you look closely, you can see the bottom of the black cage appears melted. The camera wouldn't focus well and I wasn't gonna shove my phone inside the tank, but you can see what I'm talking about. Sorry for the shitty video. I had inhaled plenty of gas fumes by that point.


Has someone done a weird repair on this tank? Maybe they cut the bottom of the black plastic cage off, inserted a ping pong ball, then plastic welded the bottom? Or is this a normal piece of equipment on early tanks? I can't really think this would do a damn thing in a rollover, for example.

Mine looks different than this next picture I grabbed from another thread. His is broken from attempting to remove it. He mentions a spring and you can see the valve is white, no ball. His is a 1999 model TJ.

99 tj tank.jpeg

(Here's his thread for credit. https://wranglertjforum.com/threads/stuck-on-fuel-tank-issue-for-my-1999-tj.55740/ )

Can anyone with some experience offer their thoughts on mine? Is it rigged with an orange ping pong ball to prevent splash back? It sounds weird, but after some of the stuff I’ve found with this Jeep… it’s possible.
 
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someguysjeep

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some claim they are roll over valves but i'm not convinced of that. i think it's more a back surge prevention.
in that pic it's been broken out and you see bright light shining in. the white thing with the yellow bottom in the top of the tank is a roll over valve.
 
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MountaineerTom

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I think that’s the stock configuration on the early models. I can’t remember what year they changed it to the white one you thought was in there. It looks like one I seen in a junk yard a few years back. I thought I may have found one with the white removable cage, so I was going to get it just to have. Turns out it looked just like that. The ball is probably discolored from the years of fuel.

1636888728784.jpeg

1636888763188.jpeg
 
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matkal

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I think that’s the stock configuration on the early models. I can’t remember what year they changed it to the white one you thought was in there. It looks like one I seen in a junk yard a few years back. I thought I may have found one with the white removable cage, so I was going to get it just to have. Turns out it looked just like that. The ball is probably discolored from the years of fuel.

View attachment 290314
View attachment 290315
Look at that crossmember......... :cry::cry::cry:.......it's beautiful. (sorry, I'm having a moment:LOL:)
 

mrblaine

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some claim they are roll over valves but i'm not convinced of that. i think it's more a back surge prevention.
in that pic it's been broken out and you see bright light shining in. the white thing with the yellow bottom in the top of the tank is a roll over valve.
I could be wrong but I thought the ball was to limit how full the tank fills. When it floats up, it restricts the opening and provides resistance to kick off the filler nozzle from the gas pump. It isn't sealed, it isn't spring loaded in early ones and the only other thing I can think of that it might do is prevent siphoning which it does very well but I don't see the factory caring much about that.
 

mrblaine

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Look at that crossmember......... :cry::cry::cry:.......it's beautiful. (sorry, I'm having a moment:LOL:)
Look a bit closer. The rear bumper is crumpled and then the upper U at the spring perch is very highly deformed which means that wheel arch is totally ruined.
 

someguysjeep

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is that the local pic-a-part?
they wanted to much for the newer body mounts so they settled for the pump strainer?
 
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MountaineerTom

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That was in Savannah, GA a few years ago. It was like that when I walked up to it.

6936AE0B-B8DF-414B-8080-709D26175EDD.jpeg
 
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Tim_with_the_tj

Tim_with_the_tj

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I think that’s the stock configuration on the early models. I can’t remember what year they changed it to the white one you thought was in there. It looks like one I seen in a junk yard a few years back. I thought I may have found one with the white removable cage, so I was going to get it just to have. Turns out it looked just like that. The ball is probably discolored from the years of fuel.

View attachment 290314

That one has a spring, but does looks like it has a ball like mine. Thanks for the pic. Mine is an early 96 build date.

I could be wrong but I thought the ball was to limit how full the tank fills. When it floats up, it restricts the opening and provides resistance to kick off the filler nozzle from the gas pump. It isn't sealed, it isn't spring loaded in early ones and the only other thing I can think of that it might do is prevent siphoning which it does very well but I don't see the factory caring much about that.

This is what I was thinking too. The only thing the ball seems good for would be anti-splash/restricting the tank when near full. I think you could still siphon my tank since the ball has no spring. It could be pushed down without any resistance if it were floating. (Edit: it would be a real bitch to siphon it, IF you could get a hose past that ball and cage.)

The question is, how did the ball get jammed up into the top of the cage where it lives? Because it was for sure choking out my ability to fuel the tank when it was lodged at the top like that. I’ll report back after I test if I’m able to fill the tank normally now.
 
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Tim_with_the_tj

Tim_with_the_tj

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Results are in. I fueled up the Jeep this morning.....and the problem is NOT fixed. Sigh. I can run the gas pump at full speed now, but I still can't get a full tank into it.

Here's what happens:

Low fuel light illuminates on the dash. Pull into a gas station and start fueling. Once the meter reads about 8.75 to 9 gallons the fuel nozzle kicks off. From there, you can only get a little more fuel into the tank if you run the pump very slowly. Once the meter reaches about 10.5 gallons the nozzle will kick off again with gas spilling out, down the side of the Jeep. Fun. The fuel gauge on the dash reads just a tick over 3/4 tank at this point. (Early tank, it's only 15 gals). That's all you can get into it. Same as before.


What I've done so far:

Removed the rubber filler neck hoses (from tank to body) to check for blockage. They were clear.

Replaced all the vent hoses coming from the tank. This includes the two vent hoses coming from each tank vent/rollover valve on top of the tank, the plastic Y fitting, and the smallest vent hose that connects to the hard line at the frame. (Hardline runs to engine bay charcoal evap canister. Picture shows the old hoses.)

IMG_5814.PNG


Vent hoses are not pinched when tank is installed. Hoses in the engine bay going to evap canister look good. Canister has no visible problems.

Freed up the floating orange ball inside the tank filler neck, as shown in the video in post #1. The ball was stuck at the top.

Checked the tank vents/rollover valves by hand when I had the tank down. Reached my arm inside the tank. Each valve has a piece on the inside of the tank that moves up/down in the event of a rollover, to act like a check valve I'm assuming. The diaphragm piece on each valve moves freely up/down by hand.

Attempted to fill the tank with the smallest vent line disconnected from the frame hardline, in order to vent the tank to atmosphere while fueling up. This made no change. That line probably isn't enough venting for refueling anyway.


Ideas:

Are my tank vent valves bad? That might also create enough pressure to cause the floating ball to lodge itself at the top of the filler inside the tank when attempting to fill it with fuel. Edit: main venting while refueling comes from the vent tube beside the filler neck. I've never had any positive pressure when taking off the gas cap. These smaller vent lines most likely aren't a problem.

What's going on here?
 
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Artsifrtsi

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Are you sure you don't have a 15 gallon tank? There was a thread I read on here about someone modifying a 15 gallon tank to a 20 gallon by trimming a vent line... or something to that effect. They said the actual tanks were identical in dimensions, just the 15 gallon was mechanically limited.

Found it...
 
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Tim_with_the_tj

Tim_with_the_tj

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Are you sure you don't have a 15 gallon tank? There was a thread I read on here about someone modifying a 15 gallon tank to a 20 gallon by trimming a vent line... or something to that effect. They said the actual tanks were identical in dimensions, just the 15 gallon was mechanically limited.

Found it...

Interesting thread. Thanks for the link. My tank is for sure the 15 gallon tank, yes. That’s what I mentioned before. My Jeep is an early 1996 build, 1997 SE model 4 cyl. It’s the original tank because I saw the production sticker on the tank with a 1996 date.

That thread gives me more information to go on...but still doesn't explain why my gauge only reads 3/4 full after the fuel nozzle shuts off at 9 gallons pumped into the tank from E (with the fuel light on). Then starts spilling out if I force it to 10.5 gallons pumped in. It should hold more fuel than this if it's really on E when I begin refueling. Probably should hold around 12 gallons when refueling from E with the fuel light on.

Maybe it's actually full and the gauge isn't reading correctly. It was suggested to me that my sending unit might be bad. The gauge seems to be working correctly, but it could be reading wrong. For example: it could be showing 3/4 full when actually full, and could be showing E when there's actually more fuel remaining than that. The whole gauge could be scaled down, so to speak. The tank might not actually be at "normal E" until beyond that mark if the voltage output is wrong (disclaimer, just a guess). This would seem to explain why I can't find a problem with the venting of the tank...because maybe there isn't a venting problem at all. After all, I can run the pump at full speed no problem.

One guy in the thread you linked said he usually gets 12 gallons into his 15 gallon tank when refueling from E (with the fuel light on). Mine can only get about 9 gallons in before the nozzle shuts off. Then if I trickle in more fuel it starts spilling out at around 10.5 gallons total. When I removed my tank while on E (no fuel light), I would say there were several gallons of fuel remaining. I can't say for sure how much, because I didn't measure it.

I'm gonna have to drop the tank again once the fuel level gets lower. I'll shorten the vent tube inside the tank to bump the capacity up to 19 gallons. After that's done I should be able to get more fuel into the tank. If my gauge still read 3/4 full after getting in several more gallons at the pump, then I'll know the gauge is wrong.
 
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Tim_with_the_tj

Tim_with_the_tj

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There's usually more than a few gallons of fuel left in the tank when the light comes on.

I can’t say for sure how much was remaining. A fair amount considering it was on E, but I have no comparison. I’ll probably end up changing the pump assembly when I cut the vent tube. That should cure my long start times when the engine is cold and when it sits for a while.

If the Jeep sits for 15 mins it will start up fast, but it’s a false start. It dies right when you hear it come to life and let off the key. It fires up instantly after that.

If it sits for 45 mins it takes maybe 12 revolutions with the starter engaged before it starts.

If it sits for hours/overnight it takes even longer to start. You can prime it by cycling the key a few times and it seems to help.

I dunno if it’s the FPR or the check valve at the pump (or both) that’s causing the issue. Jeep runs good otherwise. I might as well replace the whole assembly when I lower the tank again. And shorten the vent tube to make it 19 gals. I’ll get a new sending unit with the fuel pump assembly. I figure this solves all my problems at once.
 

oldbuzzard

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Carry a full gas can with you, and drive the Jeep until it runs dry (hopefully not on the freeway). Then you'll know where it really runs out of gas, and will have at least one end of your fuel gauge known. I had a Tacoma which registered 3/4 tank when full, but the bottom of the range was right, when it said empty & fuel light it had about 1.5 gallons left.
 
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Tim_with_the_tj

Tim_with_the_tj

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Carry a full gas can with you, and drive the Jeep until it runs dry (hopefully not on the freeway). Then you'll know where it really runs out of gas, and will have at least one end of your fuel gauge known. I had a Tacoma which registered 3/4 tank when full, but the bottom of the range was right, when it said empty & fuel light it had about 1.5 gallons left.
I thought about doing that, but when I had the tank down I noticed a fair amount of particles in the bottom. I didn’t have a good way to filter them so I didn’t worry about it. The fuel sock filter in the tank looks good, but I don’t wanna suck all that crap into it. I’ll be sure to clean out the tank next time. I can’t wait.
 

Derweazel

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I have the same year same build year and same exact problem filling my tank. Only get about 9 gallons max. I’m about to pull the tank for the 2nd time, did you ever solve the problem?
 

SSTJ

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Gosh, I wish I'd seen this thread sooner. I had the same problem, and the solution is described here.

Short story: drop the tank again and trim back the vent tube, not the filler tube.

Edit: But be sure your gauge isn't off. I haven't read all the posts in this thread, but there is a chance that your gauge is just reading 3/4 when it's really full, and reading E when it's really 1/4. When the light comes on, you should have 3 gallons left (12 +3 = 15). I learned the hard way (got stranded) that my gauge was indeed correct, but my tank wouldn't let me fill past 3/4.
 
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