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31 gallon tank same for sub and K5?

Discussion in 'The Garage' started by Blue85, Apr 11, 2006.

  1. Blue85

    Blue85 Troll Premium Member

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    I did a lot of searching and all I found conclusively is that the big 40-42 gallon sub tank won't fit in a K5.

    What I want to do is put a 31-gallon tank from an 89 3x4-ton Suburban in my K5. Will this fit under the stock skidplate?

    Is it the same as an '89 K5 31-gallon tank?

    I will pick it up today if it will work.

    Thanks.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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  3. Blue85

    Blue85 Troll Premium Member

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    Your diagrams are for carb tanks, but I assume the TBI stuff shares the same interchangability.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Yep. If paying anything more than you want the sender for, I'd pull it and make sure the baffle isn't broken. I went through two or three tanks that had broken baffles and just decided to go new.

    But a spare TBI sender is ALWAYS a good thing if it looks to be in ok shape.
     
  5. theperfectgarage

    theperfectgarage 1/2 ton status

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    same, no sweat.
     
  6. Blue85

    Blue85 Troll Premium Member

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    OK, it turns out I'm a dork. I drove 40 miles to get this tank. It was in solid shape (always a find in Michigan), very clean inside and had steel baffles inside. I checked some of the dimesions, but I was talking with the puller guy and I loaded it up. Got home and realized it must be the 40-gallon because it's like 6 inches too long!:doah: The width and depth are the same, which must be what I checked.

    So for an exchange, is the tank from a pickup truck the same? Can I use the tank and sending unit from an 87-91-or-so pickup? They have a pile of Chevy trucks back there.

    Or should I make spacers to back my bumper up 4 inches and move up to 40-gallon capacity? (40x$2.89=$115.60:eek1: )
     
  7. Slapperbar

    Slapperbar Retired Navy NDT Examiner Premium Member

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    You'll never get it below 1/8 tank. The pickup won't. I have a '91 'Burb w/a 40G tank.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Steel baffles sounds to me like it's aftermarket, coupled with your comment about being clean.

    The sender "length" is the problem, I don't believe (as was stated above) any of the pickup tanks are the right depth for the 31 gallon tank sender.
     
  9. Blue85

    Blue85 Troll Premium Member

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    Well I don't have a sender yet, either. I will also be getting fuel lines to match. All I need is a combo of tank and sender that will:
    a) fit in my truck
    b) accept a TPI pump
    c) not be smaller than, say, 28 gallons

    So I thought maybe I could take the tank, sender and lines from a TBI shortbed pickup? If the lines don't fit perfectly, that is probably OK. I will likely have to come up with something different to connect to the TPI fuel rails anyway. I'm also looking for ideas there.


    I found a TBI Blazer with the fuel lines on the frame, but the junkyard said it was illegal to sell used fuel lines.:confused:
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm somewhat curious on this...what's the depth of the 40 gallon tank? From U2slow awhile back, 31 gallon tanks are 12-3/4" deep. I'd be surprised if the 40's were deeper, I just assumed they'd be longer. My parts manual page shows the sender to be different, but it is entirely possible that all 40 gallon tanks that year used a different vent or something...check your 40 and see what the depth is.

    Again, all you are worried about is depth, if you find the truck tanks to be the right depth, the sender would be fine. They all use the same fastening method to the tanks, the only difference is going to be the arrangement of the pipes on the sender...vent lines, no vents, etc., but even then, I'd imagine all the TBI stuff US bound had EVAP, fuel return, etc. Right? I just don't see there being any major differences that vintage, except the tank depth.

    I don't think the TBI shortbed lines would be long enough. The tank is still on the outside of the frame towards the middle of the rig, correct? The K5 stuff reaches all the way back and wraps over towards the center of the fuel tank. I bent the stock TBI stuff up to fit my TPI app, but it's not ideal up at the front of the motor, but I'm confident it's not going to get worn through.

    There were plenty of holes in the drivers side frame already for the large self tapping screws such as used on the passenger side frame rail, I just used those with clamps to solidly mount the fuel lines. I still need the bracket to hold the fuel filter though.

    If you want to pay, you can get the Saginaw to AN adapters, but you'll need at least 4 (tank and fuel rails) plus however you want to plumb a fuel filter. That'd make 6 if you wanted to use a stock TBI or TPI filter. Last I looked those adapters were right around $8/each. Added up too fast for my cheap self, so I just took the stock lines, a hand tubing bender, and straightened then re-bent the stock lines as good as you can re-bend fuel line.

    The flex lines from the tank to frame and frame to fuel rail use the same fitting as GM FWD junk, and those are real easy to get in the wrecking yards. Most are very similar in length to the GM stuff, but I stumbled across a set that was a few inches longer, which can make routing a bit easier.
     
  11. Blue85

    Blue85 Troll Premium Member

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    This tank measures about 12.5" from the bottom of the tank to where the sending unit connects.

    I know I have pumped pretty close to 40 gallons into my Dad's Sub before, so I have a hard time believing there is a general problem with using the whole capacity.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Hmm, sounds suspiciously like the 40 gallon and 31 gallon sender are the same depth. If I was home I'd pull one of my 31G spare senders out and measure the depth to say, the fuel pump lower bracket to get you an exact length.

    It still sounds real close to me, it would be a lot cheaper for GM to run the same depth senders (even if different part numbers, some of the components could be the same) in teh two tanks. I can't see any reason one tank would need to be a 1/4" or so deeper than the other.
     
  13. Blue85

    Blue85 Troll Premium Member

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    It sounded like you said "spare sender"...
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    Heh, sorry man, no way I'm going to part with the ones I've got. This truck leaves my posession when I die or someone blows it up. I figure in 30-40 years senders are going to be hard to get. :)

    The senders themselves shouldn't really be that hard to get, every 31 gallon K5 and 'burb made after '86 has them, but I know what it's like: when you need something, you can't find it. When you finally get one and pay a bunch, you start finding them all over the place.
     
  15. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Ever had any experience with these types of various brand aftermarket senders?

    http://www.egauges.com/vdo_sgrp.asp?Subgroup=Fuel_Senders&Cart=
     
  16. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    I bought a universal adjustable sending unit to replace the one in my K5's aftermarket tank (50 gal ) when I had the tank renu-d. I bought from a michigan company
    http://www.classicinstruments.net/
    Great guys, called them up on the phone and they walked me through exactly how to set up the unit for my setup. Made in the USA.
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't see any that will work with our trucks, since ours aren't bolt ons.

    No experience with the company though, sorry.

    I just spent about 30 minutes looking for new 31 gallon tank senders for TBI, absolutely no luck. Tons of 25 gallon ones though. :(
     
  18. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Opps, yeah, I forgot, most thier stuff is for the aftermarket, all aftermarket fuel cells,tanks etc use the standard 5 or 6 hole bolt mounting.
    rockauto.com has the sending unit, it's the real GM part. Very expensive though.
    LIke $300 :eek:

    RockAuto
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    SU504 is the "fineline" part number for the sender, $152 for it at rockauto, only place I can actually FIND that part number, although there are search results for it around $129.
     
  20. Blue85

    Blue85 Troll Premium Member

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    Yeah, I found the sending units at rockauto, but the price is really prohibitive. I will have to scour the junkyards on foot. Unfortunately, car-part.com does not let you select "sending unit" or "fuel lines". You have to select tank or fuel pump and then contact the junkyard, most of which never reply, of course.

    I looked into the pickup tanks and they are totally different, both before and after the body-style change.
     

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