LB7 Tool No Mechanic Can Live Without

bullfrogjohnson

bullfrogjohnson

Big Girl!
Nov 20, 2006
4,167
1
0
39
Locust, NC
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

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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.

IMG_20120102_183223.jpg


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.

IMG_20120102_174230.jpg


Passenger side

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Drivers side

IMG_20120102_180147.jpg


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.

IMG_20120102_174418.jpg


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.

IMG_20120102_174445.jpg
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
0
Wyoming
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.
 
sweetdiesel

sweetdiesel

That's better
Aug 6, 2006
10,390
0
0
52
Thailand
Travis

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
 
durallymax

durallymax

New member
Apr 26, 2008
2,756
1
0
Under The Hood
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.
 
R

Randy1156

New member
May 5, 2013
9
0
0
Hi Guys newbie here. Names Randy and I love the tool Travis Great Idea. this is a little about Me and my Problem. I'm sure this is not the right thread for a newbie intro but.
I'm a Hot Rod Freak 56 years old working on my first LB7 for a friend of mine his went down,
So He purchased one from I-55 auto used $5000 12 month 12000 mile warranty. Said they cranked and ran engine. He lives in Ga. I'm in Bama we swap the motor out. would not crank with out help. either Bad I know I-55 claimed injectors were accessories and they would not warranty them. long story short Bad injectors. he made a 3000 mile haul with it and noticed fuel in the oil. lots. after 5 or so oil changes on the road adding Lucas
he made it home. we hauled it back here and purchased a rebuilt set of injectors off ebay. I install all new banjo washers and parts that came with the kit. fired right up runs great. but still filling the crank case with fuel. I spent all day Saturday pulled the top covers put fuel lines back on cranked the truck know signs of leaks. any where I'm Stumped. any Ideas can the injection pump leak from the drive side into the engine ?
 
R

Randy1156

New member
May 5, 2013
9
0
0
No Codes I'm Not Sure how to check the balance rate. I have a Nephew was a world class mechanic for GM. sold his GM Scan tool. I would have to ask him I'm new to this fuel injection stuff and don't know much. He was in the shop last night when I fired it off watching for leaks. he was putting a tranny in a hot rod last night and didn't have a lot of time to help.
 
MAXX IT OUT

MAXX IT OUT

<<<IT WORKS
Mar 1, 2013
1,780
37
48
Des Moines, Iowa
You need a scan tool. How fast is the crank case filling? How does the truck run(rough) and is it smoky at idle? Who's injectors are they? If they are cheap one off of ebay, you could have a couple of bad injectors still. The biggest thing i would be worried about leaking is one of the banjo seal on the return line, so I would pressure check them.
 
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