CM2250 Poor fuel mileage

[Truckdriven]

(02-08-2022 )SemiSweet Wrote:  I’m sure you have checked or replaced your air filters?

Air filters look clean, also the Restriction gauge does not show any vacuum

[Truckdriven]

(02-08-2022 )Rawze Wrote:  fuel mileage problems aside...


A CM2250 should peak at about 36 psi or so boost. If your only getting 30 psi boost then something is wrong.

Just some guesses here ...

* could be an improperly reading exhaust gas pressure sensor, or its circuit from the manifold thru the thermostat housing is clogged up. This can cause both power, boost, and fuel mileage problems, depending on how bad it is.

* Can be that the Turbo is not adjusted high enough in the program for the make/model truck you have.

* Can be that the ecm is holding back power/torque for one reason or another (can be seen by monitoring the 'CBL_Fuel_State' setting to see if it is following the torque curve of the engine, the accelerator pedal.. or if it has a fuel derate of some kind.

* Can be a damaged exhaust turbine in the turbo, an inlet, CAC or exhaust restriction, etc.. (something turbo or air related). Could also be a boost, exhaust manifold, or egr circuit leak somewhere. Can also be the turbo out of calibration, or has issues with its control arm.

* Can be something wrong with the fuel system, not allowing it to get full fuel.

-======

Lower than normal fuel mileage issues can be caused by a thousand different things. Does the trip fuel mileage in the dash match the actual fuel mileage on paper at the pump after it has been reset and run for a week or so?.

Oh man where do I start, trip fuel mileage versus calculated either matches or the readout will be slightly higher then actual.

As far as exhaust pressure reading I replaced the sensor and the tube and it seems to be reading properly at atmospheric pressure. The old tube was not clogged I could blow air through yet

Occasionally when using the engine brake on a long downhill at higher RPMs I will get a 2387 code for a short time. Also any time the engine brake is on at higher RPMs there is a slight fluctuation in Turbo pitch, it will boost about 36 PSI. The turbo calibrated without issues, if it were a damaged turbine wouldn't I hear a chaffing or irregular sound?

If it were in the fuel system not giving full fuel how would I go about diagnosing that?

[Rawze]

(02-08-2022 )Truckdriven Wrote:  ...
As far as exhaust pressure reading I replaced the sensor and the tube and it seems to be reading properly at atmospheric pressure. The old tube was not clogged I could blow air through yet
...

It is never usually the tube that clogs up, but the circuit thru the thermostat housing itself.
ref:

Quote:...
remove the sensor and plug it back into the harness ... spray moderate amount of brake cleaner into the hole where it mounts... crank truck to see if the brake cleaner comes blasting back up out of the hole.
...

[Rawze]

Also, do you have a pyro gauge on it>?. Where is the sensor installed?. What is the pyro getting to / showing in a hard pull?.

[Truckdriven]

I did verify the exhaust circuit in the thermostat housing was cleaned through.

I do not have a pyro but would like to add one where should it be mounted before or after Turbo??

[Rawze]

(02-09-2022 )Truckdriven Wrote:  I did verify the exhaust circuit in the thermostat housing was cleaned through.

I do not have a pyro but would like to add one where should it be mounted before or after Turbo??

after turbo is fine.

[Truckdriven]

(02-08-2022 )Rawze Wrote:  * Can be that the ecm is holding back power/torque for one reason or another (can be seen by monitoring the 'CBL_Fuel_State' setting to see if it is following the torque curve of the engine, the accelerator pedal.. or if it has a fuel derate of some kind.

.

Would I check this with insite or calterm?

[Rawze]

(02-09-2022 )Truckdriven Wrote:  

(02-08-2022 )Rawze Wrote:  * Can be that the ecm is holding back power/torque for one reason or another (can be seen by monitoring the 'CBL_Fuel_State' setting to see if it is following the torque curve of the engine, the accelerator pedal.. or if it has a fuel derate of some kind.

.

Would I check this with insite or calterm?

in CT. the setting is actually 'CBL_Fuel_State'
Everything about the engine and what it is doing is mentioned on pages 53 - 57 in this document. Page 57 shows the outcomes of this fuel state setting in detail:: http://rawze.com/forums/showthread.php?tid=7677

[JMBT]

This may be a long shot, but what about a rolling resistance problem? A sticking brake or something from sitting so long? Could be on the truck or trailer. What about drive axle alignment? Maybe scrubbing a bit to much. Or even trailer alignment? Does the trailer pull straight and easy??

Just thoughts…