mack running bad

unfortunately i think i am going to have to take my truck in. am having one/multipul problems i can't seem to nail down.

started out that the truck would occasionally idle pretty rough esp when hot. and occasionally stumble and miss in the low gears taking off easy from a stop when it would miss it would either blow white smoke that smelled of raw fuel or thick black smoke. would come out of it by 6th gear and seem to run ok.

then the front jake break quit working. and the truck seemed to run rougher less max boost on the gauge and seemed to be down on power overall, egt's stayed normal. also seemed to be accomanyed by a slight loss of oil psi on the gauge (not sure if this is the sending unit or actually lost oil pressure the oil pressure and boost gauges do tend to fluctuate a few psi on this truck.) it came out of it and ran fine for a couple hundred miles front jakes started working boost came back up as well as oil psi then went back to it and never came back. changed the oil as it was past due from where i normally change it at (had 19k miles and 460 engine hours on 5-40 full synthetic) got a slight bump in oil psi seems to be running about where i would expect when due for a oil change but not where i would expect for fresh oil.

pulled the valve covers in a parking lot i have had a oil plug in the end of the rocker shaft pop out before causing a simular problem. upon inspection all the oil plugs were in place, jump power to the front jake with the engine idled up to 1300 rpms the solinoid would activate but oil would basicly just dribble out of the jakes, #6 putting out pulses of oil a couple inches tall. the rest 1/2 an inch or so do the same on the rear cyl would shoot oil 4 ft and the jakes would come on, swapped the solinoids and the problem stayed with the front.

it idles rough, hesitates and misses at lower throttle in the low gears does smooth out and run somewhat smooth down the road but rougher than normal, power seems to be down overall. it drives like it has a bad injector but it also seems to be connected to the jake problem, also not sure what would cause the lack of oil out the front jakes when activated. engine is around a tad shy of 300k on a rebuild from mack.

any idea's?

 

yeah each injector has a unit pump that is driven off the cam, then a hard line from the unit pump/electric solenoid to a injector

 

i was thinking possibly cam as well as they are a bit known for eating cam shafts but, it does not quite add up. i was watching the rockers with the engine running and the valve covers off non looked off, i didn't measure valve lift on any of them but no rockers bouncing or anything like that indicating a problem. a bad cam bearing might make sense on the jake if the same oil galley that feeds the Jake on one head also feeds part of the cam shaft, but i also feel that to be unlikely. i guess i would buy it if they told me it ate a injector lobe and a cam bearing but i don't really feel that is what is going on.

can't visually see the cam shaft or the injector lobes without removing the injector unit pumps.

 

i have never been too far into jake breaks other than solenoids and setting clearances, one thing that has crossed my mind is a internal oil leak in the jake and its causing it to try to open the jakes while under power. i would think if that was the case though that the oil leak would probably be at the solenoid seals witch looked fine also i would have expected to see a change with swapping the solenoids if that was the problem. i would also expect to see oil coming out of the jake break when not activated.

 

i guess i also would not be entirely surprised if the poor running and the Jake break are two separate issues, that just seemed to go together.

i unless i get a better idea of what is going on im probably going to try to get it into mack as soon as i can, and hope that i get a good tech that can figure it out, iv never used there shop all repairs up to this point iv done everything myself. i just hope if i do take it in i don't get someone that just wants to throw parts at it till something sticks, i can do that myself without there 100+ per hour labor rate.