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TBI tanks *are* baffled.... (plastic repair?)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by dyeager535, Mar 7, 2002.

  1. dyeager535

    dyeager535 1 ton status Premium Member

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    ...but poorly : ) ('89 TBI K5)

    Apparently GM used some type of ABS-ish plastic, which is brittle, or gets brittle. It's held to the tank floor with 4 studs and some kind of nut. As I remember seeing here, apparently the violently sloshing gas from an accident is more than the baffles can handle, and the studs shatter (yes, there are a few pieces of plastic in the tank) the bottom of the baffle, creating large holes for the fuel to drain out, rendering the baffling worthless.

    heres a hastily drawn diagram http://yeagerd.home.mindspring.com/TablePics/k5tbitank.jpg

    The baffle is about half the depth of the tank, and is open on the top.

    As I said, it's a very poor design. Effective, but made with very poor materials. Nothing like the baffles/material used in cars.

    This plastic is black, and appears to be some type of ABS(?) Quite thin, and obviously not very flexible nor stout.

    Does anyone know of any plastic repair methods that would bond both the plastic and the metal studs together, and be impervious to fuel? I was thinking JB weld of course, but not sure how it sticks to plastic..was thinking of roughing the remaining plastic up, then just filling the 1/2" holes with JB Weld, thus locking the baffle back in place on the studs as well as the floor of the tank.

    Any other ideas for plastic repair?

    BTW, using the TBI pump to evacuate the tank, about 1.5 to 3 gallons of fuel were left in the bottom, when the pump went dry.
     
  2. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Yep, I posted this same question about 3-4 months ago. End result was, tough luck. There were a few takers with suggestions like JB weld, and I considered plastic epoxy, but I don't think any of it will hold up on plastic submerged in gas. I think about the only hope would a plastic welder, and I think there is no way to get adequate access to it. Every single tank I could find (being restricted to 87/88 TBI saddle tanks {before they went inboard} didn't help) had busted baffles, including one that looked brand new, not a scratch or dent on it. So, I'm using a unbaffled tank and I'll just keep it full. Eventually I may make a tank that goes between the rails behind the cab. If so, I'll put steel baffles in it then...
     
  3. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Same deal here.

    Due to the tight working space (impossible to rivet, bond or otherwise tweak on the stuff) and the solvent nature of gas I purchased a new tank. Ouch. Wish I would have known about the aftermarket tanks then....
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Were you able to get an aftermarket one with effective baffles?
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    I thought most, or a lot, of epoxies held up to fuel. I know JB weld is used on Q-jet fuel wells, but theres no plastic there..my dad mentioned something called Marine Ez or something like that, similar to JB Weld.

    My dad's also got a plastic welding kit, but I think you have to know what kind of plastic you are dealing with, and the RV tanks he bought the kit for is polyetylene IIRC. I guess I can fish out a couple of the pieces and see if JB Weld will hold them together firmly...

    My friend also works for a plastics company, I know he has access to all sorts of adhesives, I'll check there as well for a source of fuel proof glues/epoxies.
     
  6. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I figured the different temperature expansion properties (coefficient of expansion) would cause the JB to break off the plastic (maybe even taking pieces with it if it bonded well). Also, you can only get to one side for most of the baffle. I almost tried some plastic epoxy but decided not to take a chance on doing something that would gum up my injectors or cause other major ($$$, or stranded) problems. The epoxy I was considering is some stuff I've used before, but not on fuel systems. It comes as two part putty (like play dough), you mix it together, 5-10 minutes later it gets really hot and hardens. The stuff is strong as hell and it will stick like crazy to any kind of plastic I've used it on. Like I said though, I had no idea (and couldn't find info) on it's suitability for use constantly submerged in fuel.

    On the welders, I used to have one in the body shop. We used it to fix over-flow tanks, bumpers, all sorts of stuff. You do need to know the type of plastic to select the right rod. Then it works sort of like tig, but with an iron instead of an arc torch (I know you know, but I put this in for those who may not). My problem with using it here (assuming the plastic is of a suitable type) is that (1) it will be hard (impossible?) to do it through the pickup port, (2) Getting the fuel soaked plastic clean enough to weld on (with any chance for success) would be an ordeal in itself.

    Good luck. Looking forward to hearing how this turns out. I just dug out my old <a target="_blank" href=http://coloradok5.com/forums/showflat.php?Cat=&amp;Board=blazer4x4&amp;Number=257906&amp;page=&amp;view=&amp;sb=&amp;o=&amp;vc=1>thread</a> and realized you were one of those who replied. /forums/images/icons/laugh.gif
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Unfortunately at the time, I thought GM had used the same material in the car and truck tanks. Unfortunately not. I'm hoping that maybe whatever I can find will bond steel AND plastic, that way I can "glue" the baffle to the tank floor, and fill up the holes at the same time. I figure if it sticks to the plastic or the metal of the tank floor and studs, either way its holding the baffle in place, and making the holes much smaller, if not eliminating them.

    I started contemplating in my head a "bolt together" baffle, but I think that would be very tedious to design, make and install, even though it could be made to prevent fuel from moving enough to break the baffling in the first place...I'm going to have to research all of my options.
     
  8. Boss

    Boss 1/2 ton status Author

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    I know some of you guys know my gas tank prob with the baffle breaking off. Basically, now I'm just not letting the tank dip towards 1/2 full until I save enough dough to get a new one.

    But one member here, forget his name, said that the aftermarket one he purchased from Autozone, uses a metal baffle that is very sturdy and way better than our stock plastic junk. Only cost like $125 for a 31 gal. and $119 for a 25 gal. I don't have the part # handy, but I can get it if you need it.
    Boss
     
  9. 1BAD88

    1BAD88 Registered Member

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    About a year ago my truck was running like sh*t so I dropped the gas tank and what happened was the plastic baffle broke loose and was bouncing back and forth in the tank and it beat the hell out of my sending unit .It streesed it so that the weld on top broke and would shut the pump down . Ijust cut the baffle out and put a new sending unit and fuel pump in and I never had a problem again .The only down fall is that when I take a hard corner now my fuel gauge moves a little but not much .To get an accurate fuel reading I just let the truck sit at a a stop and it reads fine ................
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    If the aftermarket tanks baffle is as effective as the stock one, I'd have no problem buying it.

    If you look at my diagram, you can see that the stock baffles "trap" fuel, so the pump doesn't go dry on hills, cornering, etc.

    But if the aftermarket stuff is just vertical pieces of steel that prevents fuel from moving front and rear, instead of actually trapping it at the pump, it will be "worthless". I know most don't seem to have any problems, but I for one, don't want to chance it. Heck, just the other day, I was low enough on gas that the truck died on my parents driveway idling. (Q-jet, so you know it ain't the carb : )

    When I'm out hunting or whatever, having to keep a half tank of gas would require a fill up everyday, and thats a 40 mile round trip. No thanks! /forums/images/icons/smile.gif
     
  11. BurbinOR

    BurbinOR 3/4 ton status

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    Dorian, if the baffles are ABS plastic, Methyl Ethyl Ketone (MEK) will weld it back together like you wouldn't believe. Now, as for how it reacts/doesn't react to gasoline I can't say.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, spoke to my friend that works for the plastic company, he says that most of the "glue" he sells actually melts the plastic back together, so I have to believe it won't be affected by gas.

    I think I can get a couple pieces and conduct a non-scientific test of how well it's going to hold up under fuel by "glueing" them, then soaking them in gas (lol) and trying to pull them apart periodically. He says he can probably identify the type of plastic fairly well if I get him a piece.
     
  13. Boss

    Boss 1/2 ton status Author

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    dyeager,

    Do you know for sure if the aftermarket ones are just verticle pieces of steel keeping the fuel from moving around, etc and not like the OE units? I don't have a clue.

    Damn, I wish I can remember who that member was that told me he replaced it with an aftermarket tank and never had a problem.......I'll do a search and PM him.
    Boss
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    I know a guy that works for autozone, wonder if he could check for me....hmmm....I don't have to buy it I guess, just look at it /forums/images/icons/smile.gif
     
  15. Boss

    Boss 1/2 ton status Author

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    Hey, if you do ask him. Let me know what he says. /forums/images/icons/smile.gif Thanks
    Boss
     

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