lb7 injector change out - Diesel Bombers

Chevy/GMC Duramax 01-04 LB7 Discussion of Chevy and GMC Trucks with LB7 Duramax Turbo Diesel Engines

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Old 09-20-2013, 10:02 AM
Diesel Fan
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Join Date: Sep 2013
Posts: 11
Default lb7 injector change out

I have a 2004 duramax with 265,000 miles on it, it is an lb7 and looks like a mosquito fogger after about three minutes at idle. I haven't found a reliable source to check flow rates, but have ran injector cleaner in tank, and the gm kind that you have to remove fuel lines to do. Still smoking. I want to make sure head gasket isn't leaking coolant into cylinder, before settling on injectors, but do have slight smell of diesel in oil and no coolant in oil. I just purchased this truck and the guy I bought it from gave me no reason to trust him any further. Luckily the price was reflective of the problems I'm having, although he didn't disclose it and I was too naive at time of purchase to understand what the problems were. I've spent about two weeks now educating myself through forums about the lb7, and am gonna have to attempt the injector swap as I can't afford to pay someone else. I'm a confident shade tree Mechanic and with the step by step processes in the forums feel this, while time consuming, is not too much to take on. Most all forums state to replace, injectors and supply fuel lines, but I have read about return lines causing problems also. Should these be replaced also? Also this truck has stock filtration, which will be changed. I have mixed info on this, from Donaldson to cat, Some say the cat 2 micron only performs at 4 micron nominal and the Donaldson is true 2 micron. Any one have any input on this. Surely gonna go with duel filter setup. Which it seems most cost affordable to make yourself. Does anyone have pics of theirs? Part numbers of the correct filter setups to use?

I don't plan to bomb my diesel too much, as it's purpose it to haul my family, boat, or 20' gooseneck with tractor , and tandom 16' trailers to deer lease 35 miles away. I want to tune it up enough to be reliable, and would really like to see it hit the million mile mark. It came with a Hypertech part number 30029. Which I would use if it would help without potentially hurting tranny, or fuel mileage. My plans currently include

New injectors/ rebuild
Need info on where to buy reliable ones at around 200.00 per injector. If possible?
Is there a test procedure for the checking solenoids, and possibly rebuilding good ones to for go replacing. Is this idea practical? Seems all new ones are reman anyways.

add air dog 2 lift pump.
Is this worth the expense as PM to save new injectors? What Psi should it be set at?

add duel fuel filter set up
need ideas and possibly pics/ part numbers of y'alls DIY setups? Also I'm concerned about removing stock filter setup, as the manual pump has already saved my hind end once. I'm not quite sure why it lost prime, but it did. Is the stock the cause of the loss of prime much of the time and should be replaced, or is it an asset to have the manual prime pump so handy?

Replace injector supply lines
Should I replace the returns also or any other for that matter.

I have to install new fuel sending unit so will be dropping tank also. Is there any other PM I should do while I have all this about. I.E. cleaning/ replacing supply and return lines? seals...

I get very small amounts of blue smoke and large amounts of white, gray currently. This happens after idle for short while. I've parked it as to not hurt pistons and other hard parts, but when I was driving, was getting very small ticking noise ( I believe injector knock) and no smoke while cruising. Heavy throttle input while moving produces typical amounts of pure black smoke. I wonder if the blue smoke reflects possible injector cups leaking and should they be removed and replaced? / Cleaned?

My funds are limited and 4000 is all I have to invest in it currently. I want to do it correct in all aspects, while improving the reliability of the injectors moving down the road. After work is complete, I plan on running rotella synthetic oil, and opti- lube fuel additive.

Any and all comments are welcomed, and if I've overlooked anything please tell me.

---AutoMerged DoublePost---

So I took my truck to a friend who has a shop but doesnt work on many duramax. Ran a scan on the engine. Have a glow plug code and thats it. He also ran a cylinder balance test they all are running about 680 +- 2. What ever that means ? He didnt really know know either. Didnt think he had the tool todo a injector return balence rates test? He said his wireless snap on scanner was 12 grand and should be able to work mircales . Talked to diesel pump and injector out of Houston they sell newreman squirtters for 195 each but didnt sound like they did much more than rebuild nozzels. And replace ball check if showed wear. Is this normal practice as I've read that ball check is the problem and where all the leaking comes from. I think for the price . These suckers should be completly rebuilt . Need answers ! Ready to buy parts and move forward on this. Please help!

Last edited by takenbylb7; 09-20-2013 at 10:02 AM. Reason: Automerged Doublepost
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Old 10-05-2013, 01:11 AM
Diesel Bomber
Join Date: Dec 2010
Location: Fool's Golden State
Posts: 1,187

wow, long read

as you may have learned, the LB7 is well known for its injector issues. the testing procedure for them is quite difficult as the return lines are internal/under the valve covers, operate at up to 26K PSI, 96 volt solenoids, etc, etc, etc. the best way to know for sure is to just replace them all since it is so labor intensive.

return lines do not need to be replaced unless they get damaged some how. the supply lines are the same but some replace them just to be sure while others clean them out. i have reused mine three times already with no problems

the only thing you need to definitely replace, other then the injectors, is the crush washers/seals. the most critical ones being on the return lines

He also ran a cylinder balance test they all are running about 680 +- 2. What ever that means ?
680 = idle RPM
+- 2. = ballance rates

+-4 in park or neutral and +-6 in drive is the spec. anything above this is out, below is good. but when it is way off or not idling then the ecm can report them incorrectly or not at all

return rates can not be tested by plugging in a tool to the OBD port. the only way to do it is disconnect the return lines and measure the flow coming out while cranking the engine over. this is a common misconception with these engines

using injectors rebuild by anyone other then bosch is asking for trouble. it takes more then reseating the check ball to get them going again.

Lincoln Diesel, Merchant and Alligator are all good sources for injectors. i did mine for less then $2K

i got mine form here: Web Store - Lincoln Diesel Specialties

hopes this helps
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Old 10-11-2013, 11:33 AM
Diesel Fan
Thread Starter
Join Date: Sep 2013
Posts: 11

Ok went with lincoln diesel for injectors, fuel filter rebuild kit and fuel lines. Good group of guys there. Bought an airdog II 100, and a goose neck hitch , four days of work but its paid off so far. A little loss in power, thinking old squirtters might have been oversized. Runs much smoother now and no smoke yippee. Lol . Just gonna watch oil level for awhile to insure nothing leaking and put some miles on it !
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