• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Duramax LB7, the fussiest diesel on earth!

MetalMaineak

MetalMaineak

New Member
Messages
10
Reaction score
11
Location
Limestone Maine
After the hair pulling experience of getting a LB7 to start after changing the CP3, I came to the conclusion: If you don't have your toungue in the exact proper place in your left cheek it's not going to start! LOL If it wasn't for my OBD II having a FRP readout on live data I would still be trying to get it started. It was trapped air in the junction block. Ended up resorting to some "old school" tricks to get it out. The "by the book" priming and cranking method was getting me no where. My unorhodoxed method of isolating, deadheading, cranking & bleeding only took around 20 minutes to get it started. If that wasn't frustrating enough, check out my next thread
 
The frustration continues...... Gonna need some help with this one. It ran good for a couple of days so I decided to try out my new PPE tuner. I chose position 2 tow haul (90 hp increase). It ran great after, in fact I was pretty impressed with the throttle response, the increased acceleration, and improved tranny performance. I also installed an EFI live monitor. It does some diagnostic scanning, OBDII code reading and clearing, and engine gauges. So I checked inj. balance rates all were in spec.(2,5&7 were on the hi side but still in.) A couple of days later I got back from the store, put it in park, left it idling, and about 5 min later she started running like crap. I mean knocking,misfiring, the works. Checked the inj balance rates, they were all over the place, and I had no new codes Shut her down, then restarted it, and it was back to running fine again! So now I,m thinking, it reset itself, must be something to do with the FICM, ECM, or their connectors. But I have no codes. I removed the tuner program and put it back to stock. Checked all rellevant grounds. All good Checked the wiring, found one of the pink FICM ignition wires chafed through at the camlock connector on D/S. Repaired. Even did the "ice pick" trick on the inj connectors. The problem isn't as bad. While going down the road its fine, it doesn't go into a fit until it is stopped and idling . Any thoughts? Please help me. My poor old brain is turning to mush! LOL
 
The lb7 is well known for injector issues due to the VOC design. Most of the time rough idle, misfire, smoking, hazing ect can all be traced to bad injectors. But you need to confirm the supply side of your fuel system is good. Due to the duramax not using a lift pump it likes to suck air from cracked/rusted lines or bad seals in the primer. You had priming issues so it test that thoroughly. Also I see ALOT of wiring issue on the duramax. But that should set a code most of the time.

Do your self a favor and put a lift pump on that truck. It will save your pump.
 
Rockabillyrat said:
The lb7 is well known for injector issues due to the VOC design. Most of the time rough idle, misfire, smoking, hazing ect can all be traced to bad injectors. But you need to confirm the supply side of your fuel system is good. Due to the duramax not using a lift pump it likes to suck air from cracked/rusted lines or bad seals in the primer. You had priming issues so it test that thoroughly. Also I see ALOT of wiring issue on the duramax. But that should set a code most of the time.

Do your self a favor and put a lift pump on that truck. It will save your pump.
Click to expand...
I should have mentioned that I've already installed a PPE lift pump by the tank and replaced all the fuel lines from the tank to the engine, also dropped and cleaned the tank itself. I don' t get so much as tiny bubble of air from the fuel system. I've learned the hardway(LOL) to check for air right off the bat. I can see why they have electrical issues. I have a spare engine harness I've been exploring. I have never seen as many factory splices in a harness in my life!! There is 2 factory splices in 1 of the pink ign. wires to the FICM and 1 in the other! Not to mention the O/B & O/W inj power supply wires and grounds. As much as I hate to, I'm going to open up the harness on the truck and check it wire by wire. Thanx for the feedback man. It's nice to know that I'm looking in the right area!
 
I've always found my LB7 to be anything but picky. Efilive doesn't make a monitor, I'm guessing you meant edge cts or similar. As to balance rates, you have to correct them for them to mean anything. Many people overlook the fuel rate which is the most important number to know.
 
Yes it's an Edge cts, had EFI on the brain at the time. Can you help me with the B/R correction? Also where should the fuel rate usually ?run Thanks for the info. Not pickin' on the LB7 exclusively seems like all the common rail diesels have their days! LOL. I come from the days of all you needed the battery power for was to turn the starter to run a diesel. Pushin' 60 and still learnin' I went from points and carbs to buildin' stand alone harnesses for LS eng. swaps. also doin' hemis. I'll learn these diesels.
 
MetalMaineak said:
Yes it's an Edge cts, had EFI on the brain at the time. Can you help me with the B/R correction? Also where should the fuel rate usually ?run Thanks for the info. Not pickin' on the LB7 exclusively seems like all the common rail diesels have their days! LOL. I come from the days of all you needed the battery power for was to turn the starter to run a diesel. Pushin' 60 and still learnin' I went from points and carbs to buildin' stand alone harnesses for LS eng. swaps. also doin' hemis. I'll learn these diesels.
Click to expand...
Several other sites have copied it as there own(don't mind them putting the info up, just give credit where it's due), but here's my original write up I did.

Proper way to check balance rates

It drives me nuts to hear people say there balance rates are good, so how can they have bad injectors? Well they might THINK there balance rates are good, but in reality they can be quite the opposite. Balance rates are nothing more than how far off of the average fuel flow each injector is. All...
www.thetruckstop.us
 
You must log in or register to reply here.
Back
Top