LB7: Why won't it start!?

[slipagnt]

I just put my lb7 back in the truck but it won't start. I sure could use some suggestions from you guys. While it was out it it got head studs, new heads, II 90hp injectors, Airdog 2 165, intake heater delete, water pump, glow plugs, and 2 new optima yellow tops. I have verified fuel to the rails. I have only one DTC P0540 (intake air heater). Everything seams to be happy but it wont fire. It turns over and over and over and over....

 

[slipagnt]

Anyone know how to test the ficm to see if its sending a signal to the injectors?

 

[BlkMax]

How long were you cranking? It does take a little time to get all the air out of the system.

Did you change the tuning to account for the larger injectors?

 

[slipagnt]

I've been cranking it for a while. Shouldn't it be trying to start even with a little air in the system? No tune change yet.

 

[02greysixer]

Mine had to crank for close to 2 minutes before it finally fired up. A minute or so without glow plugs to build oil pressure then almost another minute to get all the air out of the rails.


Sint frum tha orijinul smert fone

 

[slipagnt]

Oh yeah, way past that. I figured it was air but I'm thinking something different now. I've run out of fuel before and had to crank for a while but nothing like this.

 

[BlkMax]

It does take some time to clear out the air. Is your AD set up to run while cranking?

My question about the tuning is based on quantity injected when, I haven't run larger injectors, but timing and duration of pulse with the larger injectors may be a factor....just a thought, I have no experience here. Have you checked the bail connectors and injector connectors? It could be wiring....

 

[slipagnt]

Yes, it's on a fuse that's switched with the key on. I can hear it running while I'm not cranking. It will push fuel from the filter housing bleed screw ( if loosened) and the test port schrader valve.

 

[slipagnt]

I have checked the bale connectors at the ficm and ecm for bent prongs. Nothing there.

 

[slipagnt]

Iv'e heard it was pretty rare for a ficm to go out. Maybe not so rare?

 

[slipagnt]

What are the chances the cam sensor and crank sensor have the same plugs? I'd go look but it's raining pretty hard right now.

 

[cafryer]

If of those were hooked up wrong you should get a code. I also would bet its air i just put injectors in my 03 it sat for a year and a half without running it took a long time cranking it before it would start.

 

[blk smoke lb7]

With the key on check to see if you have power at either the orange wire or the pink wire i cant remember which is hot at on and which is hot at cranck or it might be both orange might be passenger side and pink drivers side i can not remember for sure its been a long time since i had my problem,also if your injectors could be sending to much fuel back to the tank,i dont remember if its 1000 psi or 1500 psi the ficm needs to see before it will even try to fire the injectors cant remember his proper name but Johnny770 just installed new injectors from gm and i believe he had 2 bad injectors returning the ful to the tank. Bullfrog has that pump you can use to find out if you have an injector leaking by i believe you can check each side and if you find 1 side leaking down you can pull that valve cover and start checking 1 by 1 to see which 1

 

[slipagnt]

You guys know of any way to check the ficm pulse to the injectors? In the mean time I'll keep cranking.

 

[blk smoke lb7]

You guys know of any way to check the ficm pulse to the injectors? In the mean time I'll keep cranking.

Yeah check the orange wire and the pink wires you can check at the ficm or rite at the injector harness try the harnes 1st and check it plugged in or it will set codes.I will head out to the shop and see if i can find my photo copy of the wiring scamatic to be sure

 

[blackdirtymax]

Do you have a way to check rail
Pressure ? Who adjusted the valves if you pulled the heads off ? Doesn't take much for a duramax to run , compression , crank and cam signal , and fuel . If you got all three it has no choice but to run. I would first see if you are building rail pressure while it's spinning over , if not I would be looking for leaks . Then move to compression and see where that takes ya. Make sure you don't have any moisture in any of those bale plugs or in the ECM plugs , had that happen on a lly .


Built motor , duel fuelers , 60's overs , gtx4202r

 

[slipagnt]

Very nice. That would help alot.

 

[slipagnt]

i built the motor myself. my first common rail but not my first motor. the valve lash was adjusted within GM spec. if the fuel pressure sensor doesn't see 1000-1500psi the injectors wont fire? that sounds like what's going on. i don't have efi live or a tech2 to see psi while cranking.

 

[slipagnt]

i should see 96 volts to ground with the key on right?

 

[sweetdiesel]

You might have a stuck injector Hard to see heats going on with out a scan tool

Do you have any spare inj lines that you can cut and weld shut, I just did that to find my injector stuck