Lb7 engine cranks but will not start

[2trout]

subd

[Cowansauto]

Something odd is going on with the DLC system and/or BCM. Using a TECH 2, the display would read (Unable to connect or whatever it says. We found no codes in the BCM or in any other system. We went through some of the tests for the BCM and the PASSLOCK system. There is a valid code there. He thought he saw the code read "0" once but go back to "10" afterwards. I never saw this, but he thinks the PassLock sensor inside the ignition swith housing has went bad. I have my doubts and would rather check the functioning of the whole PASSLOCK system first before just replacing it. Of course once again, I dont have a good enough scan tool to do all of that.

ALso like I mentioned earlier, my Craftsman scan tool flashes the "CCM" light which in the manual says that system hasn't completed its system check yet and "Aux Input Status OFF".

[01 D_Max]

Continue to work on finding codes and making sure the ECM, BCM, TCM, and FICM are in working order.

But...Because you have no obvious codes I would spend even more time finding your fuel issue. Your FPR should be working alright. Now you need to try pressurizing the fuel system before the CP3. Do you have any kind of lift pump you can hook up? Pressurizing the fuel going to the CP3 will eliminate any air coming into the lines. It may even leak out of the line at the point causing the issue. This may allow you to bleed the system and have consistent fuel to the injectors.

Hooking up a lift pump is the best an most perminent way to eliminate fuel issues, caused by a leak. However you can test for the leak by pressurizing the system in different ways.

-Using a shopvac's pressure side and a rag on the fuel fill tube.
-Using a air nozzle and compressed air, and regulate the pressure to 10psi or so. Seal the opening around the nozzle at the fuel fill tube.
-Splice in a electric/hand crank fuel pump of any kind temporarily.
-Or use compressed air regulated to 10 psi and make a fitting on the fuel cap for a perfect seal. Pick up another fuel cap for cheap at your local parts store as a replacement.

I am pushing you towards the fuel leak because there should be NO air anywhere in the fuel lines. You have a ton of air, and there is no way the truck will run without constant fuel pressure, even if you do find an electrical issue.

[2trout]

Originally Posted by 01 D_Max

Continue to work on finding codes and making sure the ECM, BCM, TCM, and FICM are in working order.

But...Because you have no obvious codes I would spend even more time finding your fuel issue. Your FPR should be working alright. Now you need to try pressurizing the fuel system before the CP3. Do you have any kind of lift pump you can hook up? Pressurizing the fuel going to the CP3 will eliminate any air coming into the lines. It may even leak out of the line at the point causing the issue. This may allow you to bleed the system and have consistent fuel to the injectors.

Hooking up a lift pump is the best an most perminent way to eliminate fuel issues, caused by a leak. However you can test for the leak by pressurizing the system in different ways.

-Using a shopvac's pressure side and a rag on the fuel fill tube.
-Using a air nozzle and compressed air, and regulate the pressure to 10psi or so. Seal the opening around the nozzle at the fuel fill tube.
-Splice in a electric/hand crank fuel pump of any kind temporarily.
-Or use compressed air regulated to 10 psi and make a fitting on the fuel cap for a perfect seal. Pick up another fuel cap for cheap at your local parts store as a replacement.

I am pushing you towards the fuel leak because there should be NO air anywhere in the fuel lines. You have a ton of air, and there is no way the truck will run without constant fuel pressure, even if you do find an electrical issue.

beat me to it!...totally agree, above all, get the fuel running properly, the engine can run with codes, worry about those after the engine is running!
No matter what you do now with codes, no fuel = no running engine!

[01 D_Max]

Any updates so far on the fuel system Aaron?

[comeeonn]

Subbin to this.


Sent from the drivers seat of a Mack truck

[2500Sierra]

I'm no expert but would there be any way for him to test if the injectors themselves are getting signal to operate, with a noid light or a DVOM, or something.

[Cowansauto]

Breaking News!!!! She lives!!!

A different guy came over and hooked up the Tech 2 and hooked up the vacuum gauge to the test port. After noticing some slow cranking on my charger we bumped the amperage up. After the bump,for some unknown reason, it cranked up and started running as smooth as one that's driven daily. Balance rates were really poor and had a roughy idle. After a few minutes they'd started to level out. I haven't put it in gear yet though. The fuel filter separator was leaking on the bottom and I have a new sensor and filter to install. The got the vacuum gauge on the test port up to 8 or so and it stayed at 2 for awhile and then dropped some. I had already orderd the orings and seals to rebuild this anyways off eBay.

Balance Rates- after initial 12 mins of running. First time I heard it running!
1 -2.3
2. 0.7
3. -1.7
4. 3.7
5. 1.3
6. 1.9
7. -1.6
8. -1.8
I'm going to go tomorrow, drain the oil again, add new oil and filter.

Although I still have a long way to go, I want to thank all the board members for there help, especially the ones that have delt with my PM's!

[comeeonn]

Awesome! Glad she's finally running for ya. Rates look good too!


Sent from the drivers seat of a Mack truck

[01 D_Max]

That's great! This shows how good the Duramax is... I am glad it was cheap and not very involved.