Duramax Diesels Forum Truck of the Week
Old 01-02-2012, 06:50 PM
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bullfrogjohnson bullfrogjohnson is offline
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Default LB7 Tool No Mechanic Can Live Without

If you have owned and LB7 and do your own work, you have seen this picture before. One of my biggest LB7 fears is fuel in the crankcase. Everytime I have pulled injectors and return lines, I worry about leaks from the banjo seals. Either that, or I have seen trucks that had slow fuel dilution over time, and I wanted to figure out whether it was a leaking return or cracked injector body. I stumbled across a gm spec for the LB7 fuel return system. GM says that the fuel return system under the valve cover should 15inHG of vacuum, so I came up with this rig

It consists of a Mighty Vac hand held vacuum/pressure gauge and the clear tube it comes with, the end of an old lb7 fuel return line, fuel return line bolt and banjo washer.

Install the fitting on the fuel return outlet of the cylinder head. The passenger side port is on the inside front of the head. The drivers side port is on the inside back of the head.

Passenger side

Drivers side

Once you have finished you fuel system repair, you can check the return line system by pulling 15inHG vacuum and watching for 30 seconds. If one didn't seal off, it will show its ugly face. There is no more putting the whole motor back together and crossing your fingers that everything sealed up.

If you have one that does not seal up, you can pressurize the return system to no more than 15psi. Squirt some oil around each return bolt banjo seal, and you will see the air bubbles coming front the leaking seal.

03 CCSB lb7
06 2500hd ECLB 6.0 gasser

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Old 01-02-2012, 06:53 PM
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rgullett83 rgullett83 is offline
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very nice

Mine: 01 CCSB Siverado frame off restored with various parts from 01-06 built lly motor, built 03 trans, 2xcp3, 100% exergys, billet s366 and much more that I wont fill this space with...

Hers: 07.5 CCSB GMC Sierra SLT LMM, XD Spys, Tuned and deleted
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Old 01-02-2012, 07:06 PM
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Cool! Great idea, thanks Travis! Every time I do an LB7 injector job, Im always paranoid that im going to spend hours getting it all back together, only to find that I have a leaking return line. Knock on wood Ive never had a problem, but I think Ill be making one of these setups ASAP.

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Old 01-02-2012, 07:12 PM
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That's awesome Travis!
2001 chev ec/sb 4x4. Built motor and trans.
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Old 01-02-2012, 07:15 PM
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Burn Down Burn Down is online now
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Nice Travis. Good job! I prefer to not worry about it, though I can see how it might worry you LB7 guys
04.5 CCSB ole blue, built trans, mpi twins
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Old 01-02-2012, 07:15 PM
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Evan@LimitlessDiesel Evan@LimitlessDiesel is offline
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Great idea, I know I will be making one up.
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Old 01-02-2012, 07:35 PM
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Way to go Travis! Nice work!
"BBT" 2003 GMC CC/SB 4x4

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Old 01-02-2012, 08:25 PM
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Chavis, 2001 rc/lb Lots of air, Lots of fuel, Lots of spray.

2003 rc/lb zf6 South bend dual disk 64/75 compounds 30% injectors
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Old 01-02-2012, 08:30 PM
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Thats sweet!!! Im sure as hell gunna make one. Thanks travis!
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Old 01-10-2012, 09:08 PM
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sweetdiesel sweetdiesel is offline
That's better
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Great post! We did this last year on Abby trying to rule shit out and it does work great

We actually used a fitting I think it 10x 1.25 to connect the head to the pump....... It's been a while on the fitting though so don't take my word on it
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Old 01-10-2012, 09:10 PM
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Holy cow that is ingenius!!! Wish this would have been here awhile ago before I put my valve covers back on lol

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Old 01-11-2012, 06:37 PM
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1chevy02 1chevy02 is offline
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Nice !
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Old 01-22-2012, 11:06 PM
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awesome , wish i wouldve saw this a little while ago, just finished a HG job, no leaks, but im always worried. Ive had one leak, and it ruins your day.

Making one tomorrow have to do a set on tuesday. A+ great idea. Thanks.
Wife:2010 Jetta TDI "Cup Edition" Thunderbunny. Stg 2 Malone, Rawtek Straightpipe
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Old 08-03-2012, 11:33 PM
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Old 08-04-2012, 08:39 AM
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02ilduramax 02ilduramax is offline
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build it til it breaks

2002 lb7 cc/sb afe stage 2 intake, MBRP 5in exhaust, airdog-165, efi live tuned by dans diesel performance, tie rod sleeves, stage 4 trans by mike l
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