From here: Chevrolet-GMC Diesel Diagnostics

No Start or Hard Start

1. Excessive fuel restriction, check or change fuel filter
2. Use vacuum gauge, check the suction, you should have no more than 5 inches Hg at WOT (wide open throttle) or 7-8 inches Hg under load. If you have too much suction, after changing the fuel filter, the restriction could also be the sock in the tank. Too little vacuum (less than 2 inches Hg) means that it could be sucking air.
3. Check for air in fuel system, install clears lines before and after the filter housing to check for air in the lines.
4. Confirm actual versus desired rail pressure, even under crank no start conditions
5. If the above check good, then it comes down the following.
   a. fuel injectors (see injectors for more diagnostic information) Buy 6.6 Duramax Fuel Injectors
   b. high pressure injection pump – CP3 Buy Bosch CP3 Injection Pump for Duramax
   c. Fuel pressure regulator, check to make sure it is not stuck. Buy 6.6 Fuel Pressure Regulator
   d. fuel pressure relief valve (high pressure limit valve), check to make sure it is not leaking into the return system when rail pressure is 160 MPa. Buy Duramax 6.6 Relief Valve
6. Before condemning the high pressure pump you need to make sure there are no high pressure fuel leaks. Use the EN-47589 (same block-off caps as #9011 SPX Miller tools) cap set to cap off the injector rail to isolate the injectors from the injector return system.

 

From here: Chevrolet-GMC Diesel Diagnostics

No Start or Hard Start

1. Excessive fuel restriction, check or change fuel filter
2. Use vacuum gauge, check the suction, you should have no more than 5 inches Hg at WOT (wide open throttle) or 7-8 inches Hg under load. If you have too much suction, after changing the fuel filter, the restriction could also be the sock in the tank. Too little vacuum (less than 2 inches Hg) means that it could be sucking air.
3. Check for air in fuel system, install clears lines before and after the filter housing to check for air in the lines.
4. Confirm actual versus desired rail pressure, even under crank no start conditions
5. If the above check good, then it comes down the following.
   a. fuel injectors (see injectors for more diagnostic information) Buy 6.6 Duramax Fuel Injectors
   b. high pressure injection pump – CP3 Buy Bosch CP3 Injection Pump for Duramax
   c. Fuel pressure regulator, check to make sure it is not stuck. Buy 6.6 Fuel Pressure Regulator
   d. fuel pressure relief valve (high pressure limit valve), check to make sure it is not leaking into the return system when rail pressure is 160 MPa. Buy Duramax 6.6 Relief Valve
6. Before condemning the high pressure pump you need to make sure there are no high pressure fuel leaks. Use the EN-47589 (same block-off caps as #9011 SPX Miller tools) cap set to cap off the injector rail to isolate the injectors from the injector return system.

Fuel filter has been changed. Cannot check vacuum considering it is not running. Clear lines have been installed and no air in lines. Actual is near 18,000 desired is 6,000. I understand that it may be one of those hard parts but I am having trouble distinguishing what I am dealing with. Regulator could be bad considering the high pressure but that wouldn’t keep it from starting. The high pressure also leads me to believe that the cp3 is good. As for the injectors, I know they are a common issue but I am not seeing any of the common signs. No fuel in oil, no smoke out of tail pipe. No smell of raw fuel. I have checked the resistance on the injectors as well and got a consistent 0.5 ohms reading. I have also verified that the FICM is receiving power to both of its plugs.

 

Did you check the VATS and do a relearn. Had this problem. I ended up tuning my truck to delete VATS

 

Yes VATS is correct.

 

The problem, it seems to me, could be the Fuel Pressure Regulator (FPR), or could be a bad new fuel (rail) pressure sensor, or bad ECM , maybe other things.

You could disconnect the FPR and see if the fuel pressure goes really high at idle, 23K 24K or so, whatever LB7's produce. Then re-attach it and see if it comes back to commanded pressure. Watch your FRPS and see if it looks like is responding to what you are doing to FPR, detaching, attaching, etc. And then look at the attachment and do what testing you can do to figure out what's happening.

You could call Lincoln Diesel Specialties and see what they suggest, or maybe Oregon Fuel injection. I think that both of these places will give you their best advice.

 

The problem, it seems to me, could be the Fuel Pressure Regulator (FPR), or could be a bad new fuel (rail) pressure sensor, or bad ECM , maybe other things.

You could disconnect the FPR and see if the fuel pressure goes really high at idle, 23K 24K or so, whatever LB7's produce. Then re-attach it and see if it comes back to commanded pressure. Watch your FRPS and see if it looks like is responding to what you are doing to FPR, detaching, attaching, etc. And then look at the attachment and do what testing you can do to figure out what's happening.

You could call Lincoln Diesel Specialties and see what they suggest, or maybe Oregon Fuel injection. I think that both of these places will give you their best advice.

ECM is new to the truck. Didn’t have an ecm in it when purchased. It is to my understanding it should still start if the fuel pressure sensor is bad. Now would the regulator cause issues as I am having?
I only have two weekends into it so far. Hoping to figure it out and not waste anyone’s time but If not I’ll be reaching out to someone more experienced.

 

I dont think its a fuel pressure problem because you got fuel pressure. Might be the FICM or Vats.

 

VATS is good. I’m not sure FICM isn’t causing me issues. Starting to think I have a few issues it’s just determining what’s keeping it from starting then go from there.

 

Rail Pressure is getting up around 18,000 while cranking when 6,000 is desired.

The truck should never have 18K of rail pressure while cranking.

 

Have you checked to see if you have a collapsed return line? That could cause your high rail pressure and no start issue.

 

I have. I have disconnected lines to rear and ran into a jug of good diesel. Have also replaced cp3 return line and put clear line in at the filter head.

 

Double check your fuel rail pressure when cranking. 18k psi? Don't think it's allowed to build that high of pressure when not fired over. Fuel filter heads tend to get hairline cracks. It sounds like you have bad injectors. Remove the outgoing line on the cp3 to injectors, or remove a injector line or fuel rail line and install a clear hose and have someone crank the vehicle over see if your pushing fuel. Very easy to do. This will tell you if you have an issue from fuel tank to cp3/injectors. It should push fuel fairly quickly. Would fill a beer can in about 20 seconds of cranking. If it does then you need to check to see if your injectors are being triggered to fire. If so then I'd be looking at injectors.

 

It gets up there on rail pressure. That’s just the highest I’ve seen. I have a log saved on HP tuners when trying to start it. It’s a possibility filter head has a crack. I rebuilt it and didn’t notice anything but I’m not ruling anything out at the moment. It is pushing fuel. I don’t believe injectors are firing. It doesn’t act like it at least and no smoke/smell in tailpipe. No fuel in oil.

 

Did you have the ecm Vin programmed? And set up for that truck? And I didn't see ecm until just recently but to my knowledge a duramax can't build 18k psi at cranking, the ecm doesn't allow until rpms are up to build much more pressure. Check to see if you have power to the injector wire harness or have a tech 2 put on to see if your injectors are pulsing

 

ECM has not been vin programmed but is is paired to the truck. I can change the vin but I’m not sure that’ll make any difference.
I don’t have a tech 2. Have a friend that has a snap on scanner may get with him if it’ll give me more data. I’m definitely going to be checking for power to the injector harness when I’m back to work on it. Can I disconnect injector harness above valve cover and check for power while cranking or will it notice and act funny?

 

What do you mean paired to the truck? The tcm doesn't need Vin to be the same but the ecm and bcm and ficm need to be the same Vin. Those that say tcm needs to be same can't explain why my lb7 drives with zero issues with a swapped tcm

 

I did the emergency/VATS relearn.

 

You may have to relearn the vats again after changing the vin in the ecm

 

FICM doesn’t have to be the same VIN on the LB7 they are plug and play.

 

04 Lb7 purchased it knowing it wasn’t running with the intent of making it a daily. Running into a crank no start condition. At this point I’m just scratching my head

Installed new batteries
Rebuilt filter head (was leaking)
Installed new fuel pressure sensor (old one was broke)
Already had new starter when purchased

Rail Pressure is getting up around 18,000 while cranking when 6,000 is desired. I know this is a problem but should still start. No fuel in oil no smoke out of exhaust.No fuel leaks. Seems to turn over harder than I imagine It should and does not maintain over 200rpm unless both batteries are hooked to a cummins. Seems to make absolutely no difference to spray a little wd40 to it. Any help on this is appreciated

Need to use a scanner or you will chase this forever.

 

04 Lb7 purchased it knowing it wasn’t running with the intent of making it a daily. Running into a crank no start condition. At this point I’m just scratching my head

Installed new batteries
Rebuilt filter head (was leaking)
Installed new fuel pressure sensor (old one was broke)
Already had new starter when purchased

Rail Pressure is getting up around 18,000 while cranking when 6,000 is desired. I know this is a problem but should still start. No fuel in oil no smoke out of exhaust.No fuel leaks. Seems to turn over harder than I imagine It should and does not maintain over 200rpm unless both batteries are hooked to a cummins. Seems to make absolutely no difference to spray a little wd40 to it. Any help on this is appreciated

I had an 04 Duramax that one day decided not turn on. It would sit there and crank till there was no tomorrow and would never actually start. I changed literally everything. Turned out it was the truck ended up forgetting the key I and the security system was preventing start up. Had a friend reset some modules with a diagnostic computer and truck fired up right then and there made me look like a moron. You can tell if your key has a security feature if it has a little cross on the bottom of the shank of the key. This happened to me just sharing my experience.

 

04 Lb7 purchased it knowing it wasn’t running with the intent of making it a daily. Running into a crank no start condition. At this point I’m just scratching my head Installed new batteries Rebuilt filter head (was leaking) Installed new fuel pressure sensor (old one was broke) Already had new starter when purchased Rail Pressure is getting up around 18,000 while cranking when 6,000 is desired. I know this is a problem but should still start. No fuel in oil no smoke out of exhaust.No fuel leaks. Seems to turn over harder than I imagine It should and does not maintain over 200rpm unless both batteries are hooked to a cummins. Seems to make absolutely no difference to spray a little wd40 to it. Any help on this is appreciated

Check wiring harness at the brackets on left side of engine, they have a history of rubbing through at the bracket and shorting out causing no start on that model.

 

Update for everyone. It had been Ether bombed as I liked to say. Bent pushrods and broke rocker bridges. Pulled it apart and thankfully cam pin was fine. Has been running like a top for a couple weeks since I put it back together. That is until today I tried to read the tcm and smoked ficm. Going to send it out to be fixed. Thanks everyone for the help and guidance.