Mackpro

I can pull the software versions tomorrow and see what the levels are and If it’s up to date. Also what size tires are you running? These AI engines have a narrow horsepower/torque curve so high rear axle ratio and tall 24.5 tires can throw it out of the curve .

There is a new updated pipe number 21599120, also on that pipe it takes 2 o-rings on each end of the pipe.

Being a tooth off on the cam gear will set the cam position sensor code. I’ve done more than once , especially on the MP7 where they have timing marks on the front and rear of camshaft. The marks on the front of the cam are not inline with the rear of camshaft. So always remember on the MP7 to use the rear camshaft marks for timing. Luckily on your MP8 it only has timing marks on the front of camk

I found my notes on this exact problem, “No power till you turn key to start position “. Fuse/breaker number 7 in top dash fuse box is bad or blown. The one I had used a fuse and showed 12 volts on both sides( key off) but when turn key to on position one side of the fuse dropped to 2 volts

There is a ground stud welded to the frame rail behind the battery box. Check the wire from the ground stud to the negative on the battery. It’s a smaller fuseable link wire that can melt inside and cause this issue. I’ve also had the stud break loose from the frame and had the eyelet ends come looked from the cables

There was a design change around your year model. The original MP8 side cover had a grove machined into it and a rubber sealing strip that went into the grove to form a seal/gasket. They updated the side cover to a smooth surface with a metal gasket with rubber seal made on the gasket. I remember replacing the whole side cover to get the new style cover/gasket because the old string rubber seal was discontinued.

On some trucks we saw the starter solinoid shorting internally and making the engine die in a hard pull when the engine would lean over.

Here is a bulletin on this. https://static.nhtsa.gov/odi/tsbs/2018/MC-10152929-9999.pdf

“No Info” message on the cluster on thoses years is usually the J1708 or J1939 data link wires shorting in the engine harness. Had 2 in one week doing this and it was shorting wires in the engine harness behind the oil filters . New engine harness solved both theses trucks. Also check the engine ECM connectors for rotted pins due to antifreeze in the engine harness.

The oil leaks are probably the bottom exhaust manifold studs. They are drilled into the oil return/push tube area and you have to put RVT silicone on the studs if oil is seeping around then . This is only on the bottom studs. Using to long of bolts or the incorrect studs can actually hit the push tubes and cause issues

Going through my notes, not long ago I had a 460 CHN with low power complaint. New injectors, good fuel pressure, turbo actuator adjusted to 37 psi of boost , newest software. All perfect and ran great with no trailer. We wanted to replace the fan clutch because it was stuck on but owner declined . Finally he gave us the OK and once we replaced it and fixed the low power power problem. That fan sucks 30 to 50 HP on some engines.

I gotcha. Yea the boost pressure relief valve is a place to start.

The HP and torque curves are so narrow with the AC and even worse with the AI engine. With a AC 427 engine traveling on flat ground at 65 mph your RPM’s should be 1600. Someone might have swapped out rear axles ( ratios) or transmission and gotten the torque and HP curves out of wack. This was a common issue on the AI engine in the dump trucks we saw. The AC engine was more forgiving

Here is the bulletin https://static.nhtsa.gov/odi/tsbs/2020/MC-10180406-0001.pdf

There is a service bulletin on this issue. I believe that some on the reman carrier housing had to be ground down in some areas so the bracket would fit flush up against the carrier housing. I’ll see if I can find it and attach it here .

Like FJH mentioned, you need a boost pressure gauge. Just get a small liquid filled air pressure gauge better if it’s a 0-50 psi but a 0-100 psi will work, hook it to the intake manifold, there is a 1/8” pipe plug just for this . Using 1/4” air line run it in the cab and see what boost pressure your getting under a load, 33 psi is what I always shoot for on the ASET AC engines.

The green switch on the AC line by the drier is for the engine fan clutch only. The high/low pressure switch for the AC system/compressor clutch is on the drier itself. However if you have the factory option add on APADS system disregard the switch set up

With key on , AC switch on and blower motor on at least low speed, you should have 12 volts to at least one side of the connector on high/low switch that’s screwed on the receiver drier. If the system is full of R134a then you should have 12 volts going through the high/low switch to the compressor clutch. If no voltage , pull the cover off of the AC/ heater unit . Starting sometime around 2003-2004 Mack started putting a in line fuse below the control panel. What was happening is the AC compressor clutch was shorting out and it would fry the micro switch on the control panel. With the add on in line fuse , the fuse would blow and save the control panel. Hopefully yours has the in line fuse.

Mack won’t come out and say exactly what PSI of boost will derate it but they want the wastegate adjusted to open at 32 to 33 PSI. So I would think the derate level is higher than 33 psi. There were some software updates for the 460 CCRS if you were operating in above 4,000 feet.

Hopefully the Y hoses are still available. Best I remember they were pretty expensive

Screen clogged in the lower radiator Y pipe where it goes into the oil cooler. This restricts coolant to EGR cooler and it cracks . Then boost pressure is blown into cooling system when under high boost loads .

If power loss has been gradual over the years. I’d look at getting the pump timing adjusted. Timing gear train wear over time will cause the pump timing to slowly retard. I’ve seen them as much as 2 degrees below spec. I alway set them 1 to 1.5 degrees over the spec on the valve cover. Being in a RD I’d only go 1 degree over spec. CH’s and Superliners with the bigger radiators can go 1.5 degrees over. Also check you muffler. Some of the older RD’s had those small canisters mufflers that broke apart inside. And like the guys said above. Check linkage for full throttle and especially the kill leverage way forward. Chased a low power issue for over a day one time and it was the kill lever not adjusted. Also if truck has an air ride cab , be sure to check the linkage with the cab aired up. Check air filter for being put in upside down( don’t think it will even run that way though)

Good deal!!!

The EGR valve is on the RH side of the engine bolted to the exhaust manifold towards the rear . The EGR valve has about a 6 “ harness coming off of it with a 2 wire connector. This connector is usually zip tied to the very center of the back of the engine. You have to remove the lower center of the dash and remove the firewall engine cover to get to it.