Mackpro

I think in the last CBR bulletin I saw, it wanted you to look at the past history of the truck , like a failed turbo or EGR cooler . Where oil or coolant could have made it to the DPF or SCR box. This could “ poison” the SCR box. Software updates help sometimes . We have been lucky and have not had to replace any SCR boxes on our 30 CXU/Anthems yet . We did have a cracked DPF filter causing a P20EE code once , see if the exhaust stack black or clean

There is a fuse for the turbo , I can’t remember which fuse box it’s in though. Also, other sensors on the same 1939 data that the turbo is on could be shorting out causing the issue. On some year models the DEF level sensor is on the same data link as the turbo. Make sure your DEF level guage is working

I remember having lots of issues with a certain emission year group of MP7’s. I believe it was around the 14-15 year models. Engines would have lots of injector codes and not running smoothly. The wiring harness was rubbing the top front of the air compressor. Mack sent out a bulletin it at the time. It’s worth a shot, I remember using a long pry bar to lift up the harness and a mirror to look under it for bare wires , it was hard to reach .

It’s always the yellow and green wires that run between the ECM’s .

If your truck has the metal air cleaner housing that uses the air filter with the metal flange end , the housing has a alignment tab that sometimes gets bent out of the way and the air cleaner housing no longer likes up correctly with the hole in the hood. We would put grease on the rubber sealing gasket on the air cleaner housing and close the hood and then raise the hood to see if the grease transfers the the hood and the hole lines up . Also check in the hood to make sure nothing is blocking the passage ways , there was a bulletin on some of the hoods coming apart inside and clogged the air passages. Also if it has the chrome/metal side hood vents , remove them . Some of the chrome side vents had HP limits on them as they didn’t allow enough air in

Most all the CH/CX style trucks around that time had 3 wires on the chassis harness but usually only 2 wires on the fuel sending unit . The third wire was for a optional style of sending unit that was rarely used. If your dash is the flat panel dash with the old style odometer with the rolling number then the wires from the fuel tank sending unit go pretty much straight to the back of the fuel guage . If you put the two wires together on the sending unit the guage should go to full if the wires are not cut or guage is not bad . If you have the newer rounded dash that started with the CX and then used in the CH trucks and has the digital odometer in the middle upper part of the dash cluster, the fuel sending wires goes to VECU ( vechicle ECM) located in the kick panel in front of the passenger seat. Putting the two wires on the fuel sending unit on this style does nothing to the guage . You will get fault codes with this style if the wiring or sending unit is bad .

You are correct and even the ECM is the same just the software is different. Sometimes we get injectiors in Volvo boxes because the dealer could not get the same injectors in a Mack labeled box. However year model makes a big difference. There are 6 different MP7 injector part numbers and 5 different MP8 injector part numbers depending on year/emissions year model. The same with cylinder head part numbers , 5 for the MP7 and 6 for the MP8’s. The biggest screw ups I remember seeing were putting 2007 emissions year MP8 turbos on 2010/2014 emissions year engines, this caused regen issues. There are at least 3 MP7 turbos and at least 2 MP8 turbo part numbers. Then of course you have the common rail engines which are totally different as well .

The fuel return line above the air compressor swapped with the coolant line to the air compressor? I have seen it happen

On the ASET AC engines the air compressor gets is fresh air from the air filter piping going to the turbo. When the engine is run with a dirty air filter the suction from the turbo is so great tgAt it sucks oil up past the air compressor piston rings and the oil settles in the air filter piping and mouth of the turbo intake . Usually it’s a thick tar like residue. Kinda normal actually. Mack had a couple of bulletins on it but I dont know if it helped any.

All CHU, CXU and GU’s regardless of transmission type have a shrader valve on the air governor that’s mounted to the firewall just for theses situations. Airing it up at this fitting will air up all tanks including the one for the transmission.

Also , all MP engines starting 2010 (DEF fluid ) have two oil pressure sensors, one for the actual oil pressure and one for the piston cooling Oil pressure. On the MP7 they are both on the oil filter stand . On the MP8 the oil pressure sensor is on the driver side of the engine block beside the engine ECM and the piston cooling oil pressure sensor is on the oil filter stand . This leads to lots of confusion on both engines due to the location of which is which. The same sensor part number fits both engines and either location . Plus I believe this same part numbered sensor also is used on the fuel filter stand and the AHI for fuel pressure readings. And years ago we liked to keep no less than 10-15 sensors in the parts room due to high failure rate . A updated sensor came out and has been good for the past couple years.

See if you can find Mack service bulletin FSB 221-010

There were lots of service bulletins on low oil pressure issues on the MP7 engine. We sold very few MP7 trucks when I was at the dealership and the place I work for now only runs MP8 so I never got to personally dive into the issue but it was mostly in hot conditions and under a hard pull or in hills from what I remember

If ETECH. Could be “H ring” in block that holds and alings the roller lifter . It can be dislodged and can cause roller lifter to cam alignment issues

Looking in my 1989 Mack tune up manual. It list both the EM6-300L and the EM7-300 engines . And yes both show 1425 torque at 1020 rpms

This is probably of no help , But my buddy has 5 GU’s all with the 455 MP8, however all his have Allison transmissions. He’s running 24.5 full size tires and 4.19 Mack rears and runs 87 mph at 1900 rpms . Unsure of the overdrive ratio difference between the two transmissions

For CCRS and ASET style engines the fuel pressure regulator starts opening at 59 psi. Early ETECH engines had an 59 psi and later a 100 psi valve . The 100 psi valve caused some fuel in the oil issues on some trucks . If the valve sticks it causes low power and in most cases hard starting as the fuel in the injection galley flows bank to the tank

According to my AI HP chart , if you have a AMI-300 you will need injectiors and download to go to 400HP. If you have a AI-300 Engine you only need the download To get to 400.

Cam key swaps were only on early ETECH 1998.5 till around 2001. Beginning with the CCRS engine sometime in 2002 , all key ways are straight regardless of HP. But good on reminding us !

All AI engines internals are the same except the for turbo and injectors and download that determine horsepower ratings. I will have to find my AI horsepower charts to see the difference between 300 and 400 , sometimes the turbo has to be changed along with the injectiors .

What’s the T2 ( center of DPF temp sensor) temp running ? We like to see around 880 degrees. High temps in the upper 950-990 can kick out the regen momentarily and resume.

I had my buddy look up the part number and yes it is unavailable and no other dealerships show to have any in stock . The part number did crossover to a new Mack/Volvo part number but the description was listed as “Wiring Schematic “ and had a price of $650.

It is on the intake manifold on the drivers side of engine, between the middle to rear of manifold, it will have a round 3 wire plug

Yea , what happened? I loose my password to this place from time to time and sometimes take me a month or more to find it and log back in . But always like coming back here. Mack Technician did the homework and wasn’t afraid to swap parts around on the ASET engines to try to get them to run like they should.

It was a learning process for sure. I was thinking I could adjust the arm to where I wanted it and put the actuator back on and all would good, but the pressure inside the turbo would overpower the actuator and let the arm move. Also the actuator gear has no internal stop in either direction , so the gear will move in either direction somewhat freely.