Need some opinions again and I'll try to keep it short,

Truck: 1999 Dodge Ram 3500 5.9l turbo Auto 2WD. Truck hasn't ran since I bought it

Lift pump was bad so I replaced it with another stock unit (Didn't realize I shoulda upgraded but here we are).
Added a fuse/relay to the pump that uses the signal from the ECM to activate.
Re-terminated the battery cables and grounds going to both batteries with military style connectors due to voltage issues and poor fitment.
Went through any grounds under the hood that I could get easy access too and cleaned/greased em (still need to check passenger side motor and driver side ground by starter)
Pulled ECM out to clean contacts to motor and re-installed

I'm currently pulling both p1688 and p1689 codes ( and p0230 but thats the lift pump wiring), so from what I've gathered the VP44 is toast. But the weird part is how the truck is acting. If I have the relay for both the injection pump and lift pump installed, the lift pump will not run. If I remove the relay for the injection pump, the lift pump functions as it should (short bump on ignition and runs for 25ish seconds if starter is bumped). I get good signal voltage to the injection pump relay either way, but the signal for the lift pump goes from 12V to around 8ishV if the injection relay is installed. My first thought is a short or ground issue somewhere in the wiring but I'm starting to wonder if the dead VP44 might be causing this, or possibly a ECM issue.

Anybody else experienced this or have any thoughts?

 

I'm no help but please update. Doesn't seem to be a lot of Cummins talk here. You might do better at Cummins Forum or similar

 

You didn't replace the lift pump with the new update fuel pump for the fuel tank? Do you know if you are getting fuel up to the injectors? I want to try this. Crack open 3 injector lines at the cylinder head. Have someone crank the engine up to 15 seconds. That will tell you if you are getting fuel at the injector. Once you see fuel. Try starting the engine at 15 seconds. Once the engine starts and runs, tighten the injector lines.

 

Have you had any success with your diagnosis, I just changed my pumps and my lift pump is not working

 

Not yet, mine should be here sometime this week. I'll update the thread once I get it replaced.

 

Just wanted to update, the truck is up and running now. The issue ended up being a bad VP44 and after a replacement from DAP, she runs like a charm. So the diagnosis was a bad lift pump ended up causing the VP44 to fail. As for the communication issue, I believe that the ECM was not allowing the lift pump to activate due to codes 1688/1689, because the communication with the VP44 controller had failed. As for the lift pump, I will be upgrading to an aftermarket system (Air Dog, FASS, etc...) in the near future to remove any chance of the stock pump failing again. With the addition of a low fuel pressure warning kit and having the lift pump wired on a relay, it should be good for a while though.

 

Did you change both the injection pump and the lift pump?

One thing to look into is the actual ECM. It seems these trucks have a bad habit of the ECM not sending power to the lift pump. This is the main reason I ended up wiring a relay and fuse into my lift pump.

 

You could run an upgraded fuel pump that inside the fuel tank and get rid of the factory lift pump. If you don't go the in-take route, I ran a walbro fuel pump with a fuel pressure reg (25 psi) for years on my 02 cummins. I've run those aftermarket airdogs/fass, but they still fail just like the factory lift pump. I also ran a fuel pressure gauge inside my cab. Curious if you running a chip that runs a wire to the VP?