t2d2

iTrader: (8)

I originally posted this here, but it probably deserves it's own thread. There's not much info on the topic, and what little there is appears contradictory.

I swapped a '95 fuel tank into my '94 today. I thought the only catch was the level senders having different connections (swapping the senders and corresponding lids addressed that), but when I poured some fuel back in, it gushed out the banjo fittings in the bottom. I re-tried things a few times and then left it overnight to dry up so I can see better if it's still leaking tomorrow.

(Is 19 ft-lbs, per the factory service manual, really all the banjo bolts are torqued to? I expected significantly more than that, and they were torqued much, much higher previously from either the factory or P.O.'s work.)

But, I'm curious about those little holes that mecheng10 mentioned. I assumed they were just anchor points to keep the banjo fitting from spinning while tightening it, like on the brake calipers. But looking closer, they do indeed appear to be actual holes that the barbs on the banjo fittings plug.

That makes me think those little holes are the source of my sizable leak. I didn't see any sort of gasket, washer, or grommet on those barbs on either of the tanks upon removal of the banjo bolts, but it seems like there would have to be something to seal that sloppy metal-on-metal union. I can't see anything relevant on the parts schematics.

Edit: It's a long shot, but is it possible that the rubber gaskets (#77171-30030) which surround the banjo fitting are the seal? I.e., the barbs aren't designed to plug the holes, rather they let some fuel leak out for a reason beyond my comprehension, and the rubber gasket holds it in? (The tips aren't hollow, so it's not a pressure relief for the banjo or something.) Otherwise, I can't think what purpose the rubber gaskets even serve other than possibly a load/stress balancer, since the crush washers are the points of contact and seal. Then again, the old rubber gaskets are pretty shot, so I'm thinking they wouldn't have formed a seal anymore.

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I checked again today after letting things dry out, and my latest attempt at seating/sealing the bolts was no better than the previous ones. Fuel still pours out. I took one of the bolts out for a closer look, and two things jumped out at me:

1) The little pin hole is much bigger than the pin (barb). It can be wiggled around in the hole. There's no way for that to seal with a washer between the banjo fitting and tank creating a gap there.

2) The banjo fitting is smaller than the diameter of the recessed space it fits into, so it doesn't seal up what the pin hole allows out.

Additionally, it's unclear how many crush washers should actually be used. My '94 had two each on the passenger side bolts (supply and return), top and bottom, but only one on the bottom of driver's side bolt (evap return). That's the same as the '92 in the video here:

https://www.clublexus.com/forums/sou...s-of-boss.html

But, the '95 tank had two washers on each bolt. Did Lexus change the specs in '95? My whole reason for doing this was to hopefully eliminate the fuel pressure loss that was possibly due to a missing washer, which turned out to indeed be missing but maybe by design...

Also on that page, it says that the washers come in packs of three. That would only make sense if there's just one per bolt, which in turn seems like the only way to make them seal by having the banjo fitting directly against the bottom of the tank so the pin sits flush to the tank, as well. I'm not sure that would work, though, as the edge of the banjo fitting would be extremely close to the edge of the pin hole.

But wait, it gets murkier... The first schematic on that page shows six washers ("gasket") for the three bolts, same as in my copy of the FSM, while the second schematic lists 3x #90430-12010 but only shows two of them on the one bolt on the driver's side.

Has anyone successfully made sense of how these connections are supposed to be made? I thought this would be very straight forward. I don't see any difference between the '94 and '95 tanks that would explain things, and they're listed as the same part number.

t2d2

iTrader: (8)

I tried it again with only one crush washer below each of the supply and return banjos on the pass. side, and that slowed the leak by ~80%. That sort of confirms my suspicion that the only thing sealing the pin holes is the rubber gasket, although I still don't see how those decrepit old gaskets could have formed a seal or why the system would have been designed in such an asinine way in the first place. There's got to be something missing with the pins themselves, like a hose within the tank that they're supposed to fit into?

t2d2

iTrader: (8)

I decided to take a look at two more things: 1) the inside of the tank to see if there's a hose or something that's supposed to slide over the pins, and 2) the banjo fittings on the '95 donor car to see if the pins or rubber gaskets have any significant differences.



Inside of the fuel tank. Supply and return lines on the right, fuel pump on the left.

Well, that doesn't help... So, the pin hole is part of the hard line, meaning fuel is free to flow out the hole that the pin inexplicably doesn't seal. There's obviously no way to slide something over the pin from the inside to seal up the hole.




top: '95 return and evap return banjo fittings + gaskets.<br/>bottom: '94 gaskets in pretty poor shape.

I didn't get the '95 supply line fitting off yet, as it connects straight to the hard line and appears to be the same setup as the fuel filter and fuel rail connection points, i.e., hell to break loose. I'm not sure I want to try that in such tight quarters.

Anyway, the '95 pins are no bigger than the '94 pins. Fitting them on the '94 tank has just as much play in the holes. However, the significantly better condition of the rubber gaskets feels like the '95 fittings might just seal things up. I think I'll get some new fuel hose for the two '95 lines and swap them over, and try carefully peeling off the better '95 supply gasket to stick on the '94 fitting. If that holds fuel, then I know the pin holes are intended to leak and the rubber gasket is the only thing sealing the whole contraption. (Again, why then have a top crush washer if that's all held in by the rubber gasket? Is it just to keep everything from loosening up from road vibrations?)

Someone please tell me I'm missing something obvious, because right now, this is looking like a system intentionally designed to fail horribly. Which is all the more surprising that there's virtually no info on it, as it seems bound to happen to everyone eventually. If my fears are correct, then hopefully this thread will prove very helpful to others down the road.

Side note: I suppose the deteriorated evap return gasket could explain my fuel pressure loss, having a similar effect to the previously held hunch that a crush washer was missing, when in fact it would appear the pre-'95 models weren't supposed to have it.

t2d2

iTrader: (8)

I thought of another thing to check on. In looking at the inner piping pic above for the '94 tank that's out of the car, I noticed the spot welding doesn't look all that beefy at the triangular tips. What if the '95 tank that's leaking badly had those tubes break away from the bottom of the tank? I was tugging on it a bit when removing it, not realizing there were two banjo bolts on the one side... I wouldn't have thought it was nearly enough force to do internal damage, but maybe the hard lines aren't solidly attached to whatever the banjo bolt threads into, making that a vulnerable joint.



Inside of the leaky '95 tank.

Hmm, I've gotta say, it does look like there's a bit of a gap at the base of the triangular pieces, especially the lower one in the pic. One thing that's puzzled me when adding fuel back in is that half a gallon or less is enough to get it spilling out the bottom. That didn't make much sense at first with the system unpressurized, but I figured it must be getting into the hard lines somehow. It would make a heck of a lot more sense if it's simply spilling out the gap below the hard lines.

That would then most likely mean that the pin holes extend up a ways but are blocked off from the hard line itself, perhaps going into the triangular base.

I guess I'll be swapping the tanks back over tomorrow... I wanted to use the entire '95 setup to eliminate all sorts of possible pressure loss culprits such as vent lines, pump and back valve (forgot what exactly it's called), filler spout vent, etc.

Edit: Looks like the tank's hard lines were the culprit. Ugh. I swapped the original '94 tank back in and it's staying dry down below. False alarm on the banjo fitting pins, but at least now it's documented what they do and don't do! They are purely to keep it from spinning, as originally assumed. It sucked having to put the '94 tank back in, because the supply line banjo was extremely rough going. That's the one that was super duper torqued when removing it originally, to the point that the head got a bit stripped even with a 6-pt socket. Either someone worked on it previously or the threads were heavily gunked from the factory, like the fuel filter and fuel rail.

I also swapped the two '95 banjo fittings (return and evap return) over along with new hoses, and I did find that the return hose slid off with hardly any force once the pinch clamp was removed. That raises suspicions in my search for the fuel pressure loss.

Now to pressurize the system and hope it still stays dry below...