L59 fuel question

[osaltyone]

So I picked up my motor last weekend... It is a L59 from an 06 Tahoe. The guy at the salvage yard said it did not have the FlexFuel option, but the fuel rail has 2 lines. Is this normal? Do I run the 2nd line as a return if I am not doing FlexFuel?

Also there is a nylon tube with a quick disconnect on it. What is that used for?

Thinking I should pick up a book on the swap. Any recomendations?







Is there any way to get the # off the motor and track it back to a VIN? Just want to be sure I got the motor they gave me the VIN for. Verify mileage and all...

[83_shortwide]

I have the book GM LS-Series Engines: The Complete Swap Manual written by Joseph Potak. I dont know if it is any good, I have nothing to compare it too.

This book says "All oem engines are stamped with the last few digits of the VIN of the vehicle that the engine was installed in at the factory. Sometimes these numbers are useful if other identifying marks prove unreliable in engine identification.''

Looks like the numbers are on the drivers side, back corner of the block next to the flywheel.

[ls1nova71]

The black nylon line goes to the evap purge solenoid, you wont need it. Also, an 06 should be single line rail, either flex fuel or not. I belive the earlier flex fuels were double up to about 04 or 05.. might be worth checking to make sure they gave you the right engine. You'll need to run the return to the tank on a return style fuel rail.

Also if you got the PCM with it, it's got the VIN in it, but you'd have to power it up to read it.
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[ls1nova71]

Looks like it has a harness on it, it it hasn't been cut the harness will have a tag on it close to where the PCM plugs into it, and they have a build date for the harness. That should give you an idea on year.
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[nacho55]

Does it have a cable throttle body or a drive by wire?? Your fuel rail and regulator looks identical to mine and its an 2002 motor, and they changed the regulator in 03 or 04 I think.
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[Daaaanz67]

My 06 Tahoe motor is dbw with single fuel line but it's 4.8l
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[clinebarger]

A Flex Fuel engine would have stainless fuel rails not plastic. ALL L59 engines are Flex Fuel, You have a LM7 (If its a 5.3L).

Trucks & SUVs went "returnless" in 04, I doubt thats a 06 Tahoe engine.

[osaltyone]

Thanks for all the replies!

Originally Posted by 83_shortwide

Looks like the numbers are on the drivers side, back corner of the block next to the flywheel.

The only numbers I can find on the back of the block and stamped are 12567398. Can't find anything on google and nothing close to the VIN I was given 1GNEK13T76R167608.

Originally Posted by ls1nova71

The black nylon line goes to the evap purge solenoid, you wont need it. Also, an 06 should be single line rail, either flex fuel or not. I belive the earlier flex fuels were double up to about 04 or 05.. might be worth checking to make sure they gave you the right engine. You'll need to run the return to the tank on a return style fuel rail.

Also if you got the PCM with it, it's got the VIN in it, but you'd have to power it up to read it.
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So if I wanted to stay emissions legal would that line run to a charcoal canister or the extra bung on the gas tank. Yea, I am thinking they might have done a swap on me or told me it was for a different vehicle. I just have to find a way to prove it.
I do have the PCM, just not sure how to power it up and read it. I plan to send it out for work. Guess they could get it at the time. The harness has no cuts (checked that before I left). It has the white label on it, but is faded and I can't read the info on it.

Originally Posted by nacho55

Does it have a cable throttle body or a drive by wire?? Your fuel rail and regulator looks identical to mine and its an 2002 motor, and they changed the regulator in 03 or 04 I think.
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It has a DBW throttle body the # on that is 1257080 RME75-.

Originally Posted by clinebarger

A Flex Fuel engine would have stainless fuel rails not plastic. ALL L59 engines are Flex Fuel, You have a LM7 (If its a 5.3L).

Trucks & SUVs went "returnless" in 04, I doubt thats a 06 Tahoe engine.

That is what I thought stainless. I did not want FlexFuel and the guy said it was the regular version of the L59; but the return was throwing me off since he said it was from an 06... I can run it back to the tank no problem as I have the return on my brothers tank.

[osaltyone]

Here are some of the other #'s I found on the engine.



Y3R298141 I believe

[ls1nova71]

Not all flex fuel engines have the metal fuel rail, '04's were plastic. Post a pic of your fuel injector, that would be the easiest way to tell.
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[BR3W CITY]

Thats an 04-06 head casting (706) and those were actually the ones that were prone to failure (GM issued a TSB for it) for a 5.3l

With dual plastic rails and those heads, I'm saying its an 04 5.3L

[osaltyone]

I was thinking older too. wish I could prove it... going to try to do a compression test today. Moving forward with the install to make sure it runs in the warranty period.

[ls1nova71]

That's not a flex fuel injector. I'm guessing this is going to turn out to be an '03, an" 04 non flex would be a single line rail. Can you post a pic of the DBW throttle body? 2002 and older have two plugs.
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[osaltyone]

Here you go!

[gringoloco]

02 and older 5.3s weren't available with dbw, to my knowledge, this was an LQ9 only option in trucks before 03. I'm thinking 03, too, assuming these are original parts to this truck/engine...
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[usmcchevy]

You have a 03-04 LM7 there................or possibly even a LR4 (4.8)

[gringoloco]

Check the head gasket tab to verify displacement. It will be stamped with 4.8, 5.3, 6.0...

[Jonboy]

I am pretty sure some '01's were avaliable with DBW. They do have 2 plugs on the TB, though.

[osaltyone]

What is the easiest way to tell that I don't have a 4.8? I can remove the heads if I don't have to. Not something I have done before, but can if I need to.

[usmcchevy]

Originally Posted by gringoloco

Check the head gasket tab to verify displacement. It will be stamped with 4.8, 5.3, 6.0...

Originally Posted by osaltyone

What is the easiest way to tell that I don't have a 4.8? I can remove the heads if I don't have to. Not something I have done before, but can if I need to.

There is a little tab sticking off the head gasket below the exhaust ports that will be stamped with displacement. Take a wire brush to it and hopefully you can read it.
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[ls1nova71]

Pretty sure that 4.8's and 5.3's use the same head gasket, so the tag doesn't always match. The easiest way to find out if it's a 4.8 or 5.3 is to pull the heads, but you can pull a spark plug and shine a flashlight in the hole to see if the top of the piston is flat or dished. Flat is 5.3, dished is 4.8.

[68GMCCustom]

yup....'01 LQ4 in the GMC Sierra C3 (1st Denali truck) came with DBW. If you wanted a 6.0 in '01 you had to buy a 2500 or an HD...or in '01 a C3, '02 Sierra Denali followed in '03 by Chevy with the Silverado SS. All extended cab, AWD 6.0 powered... tho the Chevy got the LQ9.


I still miss my C3!

[osaltyone]

Originally Posted by ls1nova71

Pretty sure that 4.8's and 5.3's use the same head gasket, so the tag doesn't always match. The easiest way to find out if it's a 4.8 or 5.3 is to pull the heads, but you can pull a spark plug and shine a flashlight in the hole to see if the top of the piston is flat or dished. Flat is 5.3, dished is 4.8.

So when I shine a light down the spark plug hole I am not seeing anything really. Do I need to spin the motor a bit to bring the piston down to the bottom of the stroke? Pulling the plugs I noticed the drivers side set of plugs were black and the pass were white chalky look to them. Throught that was a bit odd.
I am just a bit worried pulling the heads since I have not done it before. Seen it in videos and... well on TV. I have all the tools; just might have to do it. Can I reuse all the head bolts or do I need new ones if I pull them. I assume I would just be pulling the bolts, checking then putting everything back together, with new head gasket of course.

My PCM came back as a 4.8 from a 06 Tahoe...Makes me worried and I think I need to be absolutley sure.

[68GMCCustom]

Don't reuse them...get new ones.

[ls1nova71]

X2 Never reuse torque to yield bolts.
You need the piston at top dead center, but it may be hard to tell anything if the piston tops are carboned up. Personally I wouldn't pull the heads, the bolts are not cheap. If you are doing it to prove to the yard that they didn't sell you what they said, then I would take it back and have them do it. Most places wont take back an engine that's been taken apart.
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