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Old 07-22-2009, 12:44 PM   #1
shrtbx
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ls1 swap question fuel tanks

I know there are a handful of guys that have made this swap here. I was wondering. Would i be able to still keep dual tanks with a swap like this or would i have to switch to a single fuel injected baffled tank. I have to say i am rather fond of the dual tanks for some odd reason.
thanks

Last edited by shrtbx; 07-22-2009 at 01:10 PM.
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Old 07-22-2009, 08:55 PM   #2
gchemist
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Re: ls1 swap question fuel tanks

You can keep both tanks. All you do is install a fuel pump.
Go to this website for part numbers.
http://www.hotrodlane.cc/77chevytruck/77chevy.htm
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Old 07-22-2009, 09:04 PM   #3
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Re: ls1 swap question fuel tanks

I'm in the midst of buying all my fuel system parts. Here is a write-up I did for a couple members here and on couple other forums:

Quote:
* AC Delco EP381 in-tank pumps. $69 each at http://store.getgmparts.com/fe0114.html
* Pollak high psi tank selector valve, this is a direct OEM replacement (JC Whitney p/n ZX812705U) $83
* Fuel selector switch from an 87, replaces existing dash switch (AC Delco p/n D7089C) $11.50 at rockauto.com
* Corvette filter/regulator if running a returnless/1 line system (WIX p/n 33737) $34 at rockauto.com

If you don't already have in-tank pumps, you'll need sending units:

* Dorman p/n 692027 for the driver side, $94 at rockauto.com
* Dorman p/n 692044 for the passenger side, $101 at rockauto.com

To make the connections at the filter/regulator:

The inexpensive way:
* 3/8" female connector (Dorman p/n 800121) $6.30 at rockauto.com
* 5/16" female connector (Dorman p/n 800120) $6.30 at rockauto.com
* 3/8" x 12" double ended male connector (Dorman p/n 800120) $8.20 at rockauto.com

The "nicer looking" way:
* 3/8" to -6AN straight fitting, Russell #640850 (this one is also is needed for connection to the fuel rail)
* 5/16" to -6 AN straight fitting, Russell #640860
* -6AN to -6AN union, Russell #660350
* -6AN tube sleeve, Russell #660650
* -6AN tube nut, Russell #660571
* 3/8" x 12" double ended male connector (Dorman p/n 800120) $8.20 at rockauto.com

And be sure to use a good quality high psi fuel pressure hose for connections, not regular fuel line. And use smooth stainless fuel hose clamps that look like these:

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Old 07-22-2009, 10:52 PM   #4
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Re: ls1 swap question fuel tanks

Im sure glad you had a good answer for that. I was thinking of doing the swap on my el camino but now that i see its not the bad with the truck i just might stick with it. I think it would be an easier fit with the engine bay. we will have to stay in touch and swap notes...Thats the only thing that really got my goat was the fuel system. How are you going to set up return lines?
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Old 07-22-2009, 11:10 PM   #5
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Re: ls1 swap question fuel tanks

I'm using a newer 1 line "returnless" system, so there is only one feed line going to the engine, and no return. The Vette filter/regulator has an inlet and a return on one side, and the feed to the engine on the other.

Bottom right - from tank
Top right - return to tank
Left - Feed to engine

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Old 07-23-2009, 03:45 PM   #6
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Re: ls1 swap question fuel tanks

this might sound stupid but do the pumps hook right onto the fuel sending unit? or do i have to make some mods to attach it.
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Old 07-23-2009, 03:54 PM   #7
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Re: ls1 swap question fuel tanks

Quote:
Originally Posted by shrtbx
this might sound stupid but do the pumps hook right onto the fuel sending unit?
They do if you are using the 87 style sending units. The 87 trucks had throttle body fuel injection, and the pumps were in the tank.

If yours is not an 87, you will need to get the 87 style sending units, they will swap right out with your existing ones. You don't need to upgrade to the 87 tanks (baffled), but it might be worth it. I am running TBI on my 85 right now with the stock tanks and 87 sending units. I haven't had any problems with them yet, but I never let my fuel gt below 1/4 tank. On anything I have. Old habit! I will most likely try to secure a pair of 87 tanks when I do my swap though.
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Old 07-23-2009, 04:21 PM   #8
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Re: ls1 swap question fuel tanks

good to know.. I thought they stopped making dual tanks in 86. Have you figured out your wiring stuff yet or is that on down the road. I think im gonna start getting the stuff you showed on your list. I like to have everything there before i jump into this.
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Old 07-23-2009, 04:26 PM   #9
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Re: ls1 swap question fuel tanks

That's what I'm doing now. I'm in the "hunter gatherer" stage!

87 was the last year of this body style. I was going to figure out the wiring for the fuel system when the time came, but I'll probably get wiring info from alldatadiy.com and start coming up with a plan soon.
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Old 07-23-2009, 05:21 PM   #10
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Re: ls1 swap question fuel tanks

did you have any problems getting the the fuel injected sending unit in the R.H tank? I see some but they all say L.H. tank only. Im guessin thats because the one tankers only had the tank on the drivers side.

Last edited by shrtbx; 07-23-2009 at 05:23 PM.
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Old 07-23-2009, 05:22 PM   #11
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Re: ls1 swap question fuel tanks

I was just looking at this unit. Im pretty sure i shouldnt have a problem getting the second on the passenger side in.



http://cgi.ebay.com/ebaymotors/87-90...lenotsupported

Last edited by shrtbx; 07-23-2009 at 05:24 PM.
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Old 07-23-2009, 05:25 PM   #12
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Re: ls1 swap question fuel tanks

Quote:
Originally Posted by glock35ipsc View Post
* Dorman p/n 692044 for the passenger side, $101 at rockauto.com
Rock auto
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Old 07-23-2009, 05:47 PM   #13
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Re: ls1 swap question fuel tanks

dang sorry..too excited about this. I forgot you had that in your list. Whenever i get excited and all interested like this that means that a new project is a brewin lol.
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Old 07-24-2009, 01:22 PM   #14
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Re: ls1 swap question fuel tanks

Are you familiar with the Fuel tank Pressure Sensor and level. I know that you being in colorado you might not need them. But i was told i would need them here in california becuase of your crappy emission laws.
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Old 07-26-2009, 07:41 AM   #15
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Re: 87 TBI wiring swap question fuel tanks

Quote:
Originally Posted by shrtbx View Post
good to know.. I thought they stopped making dual tanks in 86. Have you figured out your wiring stuff yet or is that on down the road. I think im gonna start getting the stuff you showed on your list. I like to have everything there before i jump into this.
Hey Guys,

FYI If you need it I have the Factory Wiring Diagram showing color codes and everything related to wiring for an 87. If needed I can post it. Let me know...

Desert

Last edited by Desert1957; 07-26-2009 at 02:26 PM.
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Old 07-26-2009, 09:33 AM   #16
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Re: ls1 swap question fuel tanks

yes please post it up man! the more info we have the better and thank you!
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Old 07-26-2009, 09:58 AM   #17
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Re: ls1 swap question fuel tanks

Heck yeah! Thanks!
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Old 07-26-2009, 02:24 PM   #18
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Re: ls1 swap question fuel tanks

Here it is....
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Old 07-26-2009, 02:39 PM   #19
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Re: ls1 swap question fuel tanks

Here is the Tank Switch...
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Old 07-28-2009, 08:27 AM   #20
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Re: ls1 swap question fuel tanks

If anybody has any questions about these two wiring Diagrams please contact me...

Desert

PS: one is the Tank Switching valve / Sending unit with pump Diagram
second is the dash switch diagram
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Old 07-28-2009, 08:44 AM   #21
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Re: ls1 swap question fuel tanks

Thanks for posting those! The only thing I need to wrap my head around is tying in the Vortec harness to the trucks harness for the switching and pumps. I still haven't dug into it yet, but I'm thinking it should be pretty easy? Right now the truck has one fuel pump relay on the firewall. I am only guessing that the fuel pump relay wire in the Vortec harness will take the place of the signal wire that currently goes to that relay?
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Old 07-28-2009, 11:09 AM   #22
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Re: ls1 swap question fuel tanks

I think your truck (If an 87) should be like mine. On the firewall there should be two relays. Not sure without looking which one is fuel pump relay. I will have to check the other pages in the wiring books I have to figure out if that is the signal wire from the relay to the switching valve. I think it almost has to be.
Just remember in theory what a relay does. Anything with a motor or a high amp draw (like a fuel pump) have a switching relay to prevent the wiring from having problems.

So back to your question, You want to know if the relay wire from the firewall , goes to the switching valve and then to the pump?

I will do the research today , might not post until wed PM...
Desert
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Old 07-28-2009, 11:23 AM   #23
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Re: ls1 swap question fuel tanks

Quote:
Originally Posted by Desert1957 View Post

So back to your question, You want to know if the relay wire from the firewall , goes to the switching valve and then to the pump?

I will do the research today , might not post until wed PM...
Desert
Yes, that's pretty much it. My truck is an 85, with the harness and everything TBI related from an 87 donor truck. But I'm installing a 5.3L/4L60E this winter, and so far that's really the only wiring question that is still not fully verified.
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Old 07-28-2009, 05:59 PM   #24
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Re: ls1 swap question fuel tanks

The fuel pump test lead on the firewall goes to the switching valve and then to the appropriate pump.
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Old 07-28-2009, 07:42 PM   #25
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Re: ls1 swap question fuel tanks

Test lead? Does that go to something other than the fuel pump relay?
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