PLEASE help me! VNL670 with an ISX CM2350 4.4 MPG!

[VNL670]

Good evening everyone. I am an O/O in need of some serious help or advice. After totaling my 2007 VNL670 with a Cummins CM870, I bought a month ago a 2014 VNL670 (VIN:157174) with a 525 HP ISX CM2350 (ESN 79646948) and a manual 13 speed. It had a CIL when I bought it. I took it to the shop in Venus, TX and here is what has been done so far, but not on the same trip. Please keep in mind that the truck started to lose MPGs around 2 - 3 weeks ago.

1. Oil change, air & fuel filters. (complete PM)
2. Oil pan gasket
3. Upgrade fuel pump inner rods from ceramic to metal with a rebuilt head unit from Cummins.
4. Baked & cleaned both DOC and DPF filter.
5. New injector DEF doser and gasket.
6. All new DEF sensors. (All sensors have been changed except the ammonia sensor on SCR)
7. New Delta-P sensor.
8. New I-map sensor
9. Exhaust gas pressure sensor (Close to the thermostat).
10. Fuel rail pressure sensor.

The issue is that after all these repairs the truck is only getting around 4.5 mpg (at the pump) cruising at 68 mph at 1400 rpm with light loads (50000lb - 60000lb) all in the South and Midwest. Currently there are no CIL on the dash or any messages. Boost gets to 35-37 on the gauge between gears and shifting or up-hill. Doesn't over heat and does not run hot like my old CM870. I fill up the DEF tank every 4-5 fuel fill-ups or roughly 4000 mile (give or take). It drives fine but just using a LOT of fuel. Ask me anything you want and if you need pictures, let me know. Any advice on what else to replace is highly appreciated.

[Hammerhead]

(06-25-2018 )VNL670 Wrote:  Good evening everyone. I am an O/O in need of some serious help or advice. After totaling my 2007 VNL670 with a Cummins CM870, I bought a month ago a 2014 VNL670 (VIN:157174) with a 525 HP ISX CM2350 (ESN 79646948) and a manual 13 speed. It had a CIL when I bought it. I took it to the shop in Venus, TX and here is what has been done so far, but not on the same trip. Please keep in mind that the truck started to lose MPGs around 2 - 3 weeks ago.

1. Oil change, air & fuel filters. (complete PM)
2. Oil pan gasket
3. Upgrade fuel pump inner rods from ceramic to metal with a rebuilt head unit from Cummins.
4. Baked & cleaned both DOC and DPF filter.
5. New injector DEF doser and gasket.
6. All new DEF sensors. (All sensors have been changed except the ammonia sensor on SCR)
7. New Delta-P sensor.
8. New I-map sensor
9. Exhaust gas pressure sensor (Close to the thermostat).
10. Fuel rail pressure sensor.

The issue is that after all these repairs the truck is only getting around 4.5 mpg (at the pump) cruising at 68 mph at 1400 rpm with light loads (50000lb - 60000lb) all in the South and Midwest. Currently there are no CIL on the dash or any messages. Boost gets to 35-37 on the gauge between gears and shifting or up-hill. Doesn't over heat and does not run hot like my old CM870. I fill up the DEF tank every 4-5 fuel fill-ups or roughly 4000 mile (give or take). It drives fine but just using a LOT of fuel. Ask me anything you want and if you need pictures, let me know. Any advice on what else to replace is highly appreciated.

These are the two issues that jump out at me.
First, great fuel mileage cannot be achieved at high speeds, but regardless, you should be getting better than you are.
Which leads to something very obvious, a CM2350 SHOULD NOT BE ANYWHENEAR THIS MUCH BOOST! Verify this is correct, and have someone who knows what they are doing verify you have the correct programming in that thing BEFORE it's too late.

[DLC]

One thing I tell guys to do is to take a windex(spray bottle) filled with some dish soap and water and spray down all your intercooler connections. Rev engine to 1200rpms or so and spray all your intercooler connections. I find leaks on most of the ISX/QSX equipped machines I see. IH trucks are bad with their shrink clamps. I'll spray down intercooler too but haven't found any leaky ones yet. It may not be your silver bullet but it's easy and cheap to do. Someone will chime in and say he's got lots of boost and won't have a leak don't bother checking. Please just check and there's one thing off the list.

[Rawze]

Just for reference there hammerhead, on a 2350 with egr still active, a couple psi higher than a demandated truck if it is using a lot of egr gas.


==========


What is the rear ratio of the truck? What is the mileage? - I did not see it mentioned.

Like hammerhead has said,.. has anyone verified that the truck has the correct program in it based on the engine ser#?. I.E.> Make sure someone did not "up the hp".

* Has anyone bothered to look at the decomp tube and verify it is not partially clogged? Reference: http://rawze.com/forums/showthread.php?t...07#pid1807

* Has anyone bothered to see if the Doser injector behind the turbo is leaking fuel?

* Has anyone bothered to pressurize the CAC and check it for leaks? -- How about pressurizing the entire engine between the intake filter and the back of the turbo and checking it for leaks as well?

* Does the truck have an after-market CAC unit on it? - Many brands of after-market CAC uints are very restrictive and cause fuel mileage losses.

* Does it have an after-market EGR cooler on it? -- Same thing, they can rob you of fuel mileage and in fact many have even caused engine damage due to excessive egr temps.

* Anyone bothered to pressurize the fuel tanks and check the lines for leaks?

* Does it pass a leak-down test? Reference: https://youtu.be/eH9GRkeozTM

* Anyone bother to flow-test or even inspect the the SCR unit for clogging?

* Anyone bothered to do valve adjustment?

======

It the mean time ...

Like Hammerhead said, slowing down to 63~ish will help -- A LOT!. So will driving by your boost gauge and limiting boost to about 15 psi or so as a good start. I am not saying this as a replacement to any fuel mileage loss problems the engine or truck may have,.. but it will definitely help mitigate losses. This is especially true while you figure out how to get the fuel mileage back up to normal levels. Better driving habits always lead to higher profits and less down time.

[snailexpress]

I will look blowby first. If truck was idling a lot it's about time to have cylinder polishing and carbon seized rings. Why oil pan gasket was changed?
How about overhead? How frequently regeneration is occurs?

[VNL670]

(06-26-2018 )Hammerhead Wrote:  

(06-25-2018 )VNL670 Wrote:  Good evening everyone. I am an O/O in need of some serious help or advice. After totaling my 2007 VNL670 with a Cummins CM870, I bought a month ago a 2014 VNL670 (VIN:157174) with a 525 HP ISX CM2350 (ESN 79646948) and a manual 13 speed. It had a CIL when I bought it. I took it to the shop in Venus, TX and here is what has been done so far, but not on the same trip. Please keep in mind that the truck started to lose MPGs around 2 - 3 weeks ago.

1. Oil change, air & fuel filters. (complete PM)
2. Oil pan gasket
3. Upgrade fuel pump inner rods from ceramic to metal with a rebuilt head unit from Cummins.
4. Baked & cleaned both DOC and DPF filter.
5. New injector DEF doser and gasket.
6. All new DEF sensors. (All sensors have been changed except the ammonia sensor on SCR)
7. New Delta-P sensor.
8. New I-map sensor
9. Exhaust gas pressure sensor (Close to the thermostat).
10. Fuel rail pressure sensor.

The issue is that after all these repairs the truck is only getting around 4.5 mpg (at the pump) cruising at 68 mph at 1400 rpm with light loads (50000lb - 60000lb) all in the South and Midwest. Currently there are no CIL on the dash or any messages. Boost gets to 35-37 on the gauge between gears and shifting or up-hill. Doesn't over heat and does not run hot like my old CM870. I fill up the DEF tank every 4-5 fuel fill-ups or roughly 4000 mile (give or take). It drives fine but just using a LOT of fuel. Ask me anything you want and if you need pictures, let me know. Any advice on what else to replace is highly appreciated.

These are the two issues that jump out at me.
First, great fuel mileage cannot be achieved at high speeds, but regardless, you should be getting better than you are.
Which leads to something very obvious, a CM2350 SHOULD NOT BE ANYWHENEAR THIS MUCH BOOST! Verify this is correct, and have someone who knows what they are doing verify you have the correct programming in that thing BEFORE it's too late.

I am going to check some time next week on the boost issue and I recently updated the ECM from EF10064.34 to EF10064.39 with no improvements to the MPG. I will keep everyone posted.

[VNL670]

(06-26-2018 )DLC Wrote:  One thing I tell guys to do is to take a windex(spray bottle) filled with some dish soap and water and spray down all your intercooler connections. Rev engine to 1200rpms or so and spray all your intercooler connections. I find leaks on most of the ISX/QSX equipped machines I see. IH trucks are bad with their shrink clamps. I'll spray down intercooler too but haven't found any leaky ones yet. It may not be your silver bullet but it's easy and cheap to do. Someone will chime in and say he's got lots of boost and won't have a leak don't bother checking. Please just check and there's one thing off the list.

That is actually going to be my next move. I am going to do that Monday or Tuesday to make sure I'm not losing any boost.

[VNL670]

(06-26-2018 )Rawze Wrote:  Just for reference there hammerhead, on a 2350 with egr still active, a couple psi higher than a demandated truck if it is using a lot of egr gas.


==========


What is the rear ratio of the truck? What is the mileage? - I did not see it mentioned.

Like hammerhead has said,.. has anyone verified that the truck has the correct program in it based on the engine ser#?. I.E.> Make sure someone did not "up the hp".

* Has anyone bothered to look at the decomp tube and verify it is not partially clogged? Reference: http://rawze.com/forums/showthread.php?t...07#pid1807

* Has anyone bothered to see if the Doser injector behind the turbo is leaking fuel?

* Has anyone bothered to pressurize the CAC and check it for leaks? -- How about pressurizing the entire engine between the intake filter and the back of the turbo and checking it for leaks as well?

* Does the truck have an after-market CAC unit on it? - Many brands of after-market CAC uints are very restrictive and cause fuel mileage losses.

* Does it have an after-market EGR cooler on it? -- Same thing, they can rob you of fuel mileage and in fact many have even caused engine damage due to excessive egr temps.

* Anyone bothered to pressurize the fuel tanks and check the lines for leaks?

* Does it pass a leak-down test? Reference: https://youtu.be/eH9GRkeozTM

* Anyone bother to flow-test or even inspect the the SCR unit for clogging?

* Anyone bothered to do valve adjustment?

======

It the mean time ...

Like Hammerhead said, slowing down to 63~ish will help -- A LOT!. So will driving by your boost gauge and limiting boost to about 15 psi or so as a good start. I am not saying this as a replacement to any fuel mileage loss problems the engine or truck may have,.. but it will definitely help mitigate losses. This is especially true while you figure out how to get the fuel mileage back up to normal levels. Better driving habits always lead to higher profits and less down time.

Hi Rawze. I rear axle ratio is 3.420MT40-14X*C and the current mileage is 429306. I updated the ECM from EF10064.34 to EF10064.39 & with no improvements to the MPG. I just wanted to make sure everything is correct and not tampered with in the ECM. And in regards to the SCR screen, Yes I had a similar problem which I fixed by replacing the DEF doser valve, but mine was not as bad. Now the turbo injector/doser I have not took apart yet & I will do that after I check the CAC with soap & water on Monday or Tuesday. I will also see if I can get it pressure tested from the turbo as you mentioned. The CAC on this VNL is OEM & so is the EGR cooler (it's red like the engine). Please keep in mind that the highest EGTs I get from this truck even during REGEN or PARKED REGEN, is 720 degrees fahrenheit. I did get under the truck for fuel leaks, but did not find any what so ever. Not even a minor leak or even at the engine. Now the mechanic that built my fuel pump and switched out the ceramic rods to metal rods, did the injector test and found no leak, so he replaced the fuel rail sensor and that issue was fixed. But i will have him do it again just to make sure. I honestly don't know if the SCR was checked for clogging or not. I will put it on the list along with an overhead valve adjustment.

[VNL670]

(06-26-2018 )snailexpress Wrote:  I will look blowby first. If truck was idling a lot it's about time to have cylinder polishing and carbon seized rings. Why oil pan gasket was changed?
How about overhead? How frequently regeneration is occurs?

Actually I don't think there is a lot of idle time on this engine because it had idle shut down after 2 minutes of idling, so I had the idle shutdown removed when I updated the software on the ECM because it was driving me crazy. There is no blowby on this engine at all (knock on wood!). The oil pan gasket was changed because it had an oil leak but later discovered the leak is actually coming from the valve cover towards the rear. I won't be able to confirm it's coming from the valve cover until I take it in to the shop and do the overhead valve adjustment on it. It is very hard for me to tell in regards to the REGEN, but they occur while I am driving (passive) or I do it while I am parked manually when it let's me. But I go thru I fill-up of DEF for every 4 to 5 fuel fill-ups.