Between the swim meet, gymnastics, cleats-purchase, run to the children's science center, and my son's 7th birthday, no resolution was to be had yesterday... I will probably try pulling the internal pump and refitting the sender first then the pump.

Regarding the bucket lid, I think I'll pull it up to the opening and cut it up into quarters and pull it out. Left intact in there, I suspect over time it would repeatedly land on the screen of the internal pump and mess up the mesh. No point in not preventing that.

 

have you figured out if the tank vent is plugged??
OR the tank has seen an issue with collapsing on itself??

 

Stan-

La la la la, trying not to hear you....

Honestly, no I haven't. I have looked all the way around the tank underneath and it's tight up against all the straps, so while it's possible that it's collapsed somewhere, I don't see where.Or it was transiently collapsed and then the vacuum was released? I don't recall there being any rushes of air when opening the gas cap, but who knows? When a tank collapses, is it obvious from looking at it externally?


Since I'm going to have to drop the straps again to pull the internal pump I can certainly drop the whole thing, I just didn't want to do that if it's really not necessary. And I'm a little nervous about pressurizing 17 year old plastic if it's already been flexed inward and back already.

 

think of the tank as a big plastic ball ,
the plastic is rather thick,
i cut one up out of the burned Euro and use a side of it for a parts washing tank I would say the tank is about 4 to 5 mm thick dropping it will give you time to inspect the tank for cracks at the T fittings and also see if there is other damage pay attention to all of the lines that connect to the tank as i would suspect one may be plugged

 

Why did I write this? I was lying through my teeth. I didn't look underneath at all. If I had, I would have seen this:



So the tank is imploded. And that implosion probably dented the fuel level sender, which should have been the tipoff that the tank is collapsed. The question is now, of course, why? One obvious possibility is that one of the vent lines is plugged. But how/why? What in this diagram gets plugged? One of the hoses, or one of those valves sticks open and intake vacuum sucks the tank down? There are only 3 connections to the tank itself- Besides the internal pump and level sender, there's only 1 'vent/equalization line (#34), which runs from an elbow on top of the tank back and around to a 'T' on the filler neck, which then continues (#32) to the expansion tank (#31). So where does the vent hose get blocked?



I did have the cradle off (and the tank moved around a bit) when I R&R'ed the external fuel pump. It was a real bear getting the cradle reinstalled- I wonder whether I'd somehow compressed the vent line between the top of the tank and the body?

Anyway, I set about dropping the tank this evening. Started off easy, actually, 4 bolts for the cradle, a 6 mm hex bolt above the filler neck (remove the rubber surround). Disconnect the flexible fuel line at the output from the fuel filter, the wiring connections at both pumps, and thread all back through the cradle opening. The tank then drops about 4 inches, and then hangs on the lateral edge of the rear bumper cover. I came across some previous posts where people have dropped the tank but I didn't want to A) remove the bumper cover, B) bend the hell out of it, or C) find the secret obstetric maneuver that allows delivery of the tank intact.....

So I decided to re-inflate the tank in situ. I made up a 'plugged' internal pump using an old dead pump:



The vent hose can be plugged with a hose clamp pliers either just after the 'T' fitting at the filler neck:



Then I made up an adapter hose to connect compressed air (5 psi on the regulator) to the hose barb on top of the old level sender (which now fits in the tank since there's just a stub of the fuel pump in there...).



Then add air and stand back while I blow up a volatile combination of gasoline vapor and compressed air:



Easy peasy, didn't even burn the house down, though clearly it got a little tense there at 0:15..... Now I just need to carefully reinstall the tank. Think I'll get it in position with the cradle and then blow compressed air thru it to make sure the vent hose is open......

FWIW, one can straighten out dents in the level sender housing with a 34mm HF socket, using a smaller socket and an extension to drive it thru:



The slide works perfectly now. Guess I didn't need a new sender after all.



Next mystery: WTF did I do to the Ott link? It was straight a month ago, I swear. Will axle hop do this?

 

I had one collapse and lodge the sender. Sitting in the sun caused to recover on its own. Sender has been fine now for a year since that happened. No lasting damage.

 

Hose # 34 is for equalizing pressure between the main body of the tank and the filler neck, so that the tank can be filled up completely. If that hose is pinched, air is trapped in the main body of the tank and the tank will not fill to full.

So the problem lies anywhere forward of hose # 32. The venting lines run all the way forward to the charcoal cannister and engine, and back towards the rear of the car. Part #25 is the air inlet for the venting system and sits in the middle under the rear bumper. Thus, you have to trace the venting system from hose #32 to part #25 to find where it is blocked (or start at #25 )

In my case when I replaced the charcoal cannister, I replaced the hard preformed hoses #18 with new flexible ones but made the radius too tight.

Did you experience air rushing into the tank when releasing the gas cap btw?

Nice tremble at 0:15

And yeah, how did you manage to get the drop link like that??

Edit: I suppose hose #34 could cause the tank to implode as well since the filler neck end really low on the main body of the tank. I remember I found the pinched hose on my car by loosening each hose consecutively and blowing through air inlet #25. When the system was blocked, couldn't force air through it. When I loosened the culprit, it was easy to blow through. That is, with the gas cap removed.

 

Rob I had to do the same thing myself a while back but as with most things you do I find my methods very crude by comparison. Great job as always.

 

I would start by looking at #26. It is the steel rigid line that runs from the tank to the charcoal canister. My car had set for a number of years before I got it so condensation may have been the down fall of mine, but in any case, the inside of line #26 had started to corrode and had plugged with rust at the beginning of the long straight run along the floor pan, and just forward of the rear wheel well.

Edit: the lid on the bowl in the bottom of my tank had come loose from one of the three clip when I pulled my sender out. Lucky for me my wife has thin arms and managed to get it clipped back together.

 

Had a little time tonight to pull the tank. The reason I couldn't get it out before was that the right rear droplink was bent and thus in the way. Pulled that and voila, out she came. It seems to have kept its shape and isn't leaking (at least when filled with water....)

I will try to get the lid back on the bowl. My 9 year old has slender arms...

Next is to figure out where the blockage in the vent system is.


They are light 16 lbs 6 oz, soaking wet. (No sender, pump, or cap)

 

Got the tank back in today but ran out of time to check the vent lines up to the front wheelwell.


I put kid #1 to work today:



The view with everything aligned:

 

Good to see the child labor laws are so lax in California. Great pic!

 

Car's back together but I'm not sure I cured anything. Spent some time sussing out the connections everywhere. This is what I checked:

-Blew compressed air (5 psi) into the vent hose behind the fuel tank- blew clear to the 'luft' connection on the front of the carbon canister.

-With the gas cap off, I blew compressed air into the vent hose on the 'tank' connection at the carbon canister- could see fuel vapors being pushed out of the filler neck.

-I checked the diaphragm in the vacuum valve near the filler neck- It held vacuum just fine.

-None of the hoses to the carbon canister or any hoses in the engine compartment between the vacuum valve and the intake mainfold are kinked in any way.

-The vacuum lines to the vacuum valve and the diverter valve are identical between the GT and the GTS, so I don't think that's an issue.

-The three connections on the carbon canister all communicate with one another, can blow air into any one and feel air at the other two. The old canister weighed 2lbs 10oz. I happened to have a new one, and it was 2 lbs 5 oz, so I installed it. (It behaved identically to the old one, all connections were in communication with each other)

So I guess I'll fill the tank and check it every 10 miles for a while to make sure I'm not re-imploding the tank. I never did identify why this was happening. Even if there was a malfunction with the solenoid-operated bleeder valve so it was open to engine vacuum all the time, as long as the charcoal canister is open to atmosphere thru the vent, it shouldn't matter.

I must have pinched the tank equalization hose the first time I reinstalled the tank, nothing else makes sense to me....

For posterity I made some fuel/vent diagrams 'cause I couldn't keep the whole thing in my head at once.

From the back to the front:

 

The the solenoid-operated bleeder valve can be tested with a diagnostic tester, but as you said it shouldn't matter. Nice pictures!

 

Ummm.... that swaybar link looks to be a little bit un-straight. Wassup wit dat?