Mackvette1

Just did a long test drive with an empty trailer and Boost hit 35 psi under full load and Performance was what I was looking for pulling good strong and quick

Could be all that is left. I have tried cracking lines and can’t really find one that is weak..would that make it lose it’s prime over night? Or maybe to big of a tip on the injector for this truck? Again I have replaced fuel lines, filters, check valve, lift pump. Thanks again

Reinstalled old injectors/factory injectors and The rough idle when away...guessing the oversized injectors need more fuel pressure so I’m going to buy the 100 psi check valve and try that

didn’t know there was one...all I’ve ever known is the check valve on the return side. It seems weird to me though because it will smooth out when I unhook the suction line at the tank. I have switch tanks and used 5 gallon buck still no change

Recently installed new oversized injectors, fuel lines, Return check valve, fuel filters and ran the overhead. Truck runs amazing going down the road 33 lbs of boost and pulls like a dream but runs like its sucking air and running ruff at idle. Seems strange but I can get it to smoothen our when I unhook the fuel supply line for a bit but no fuel suction. Seems to be on the return side if I had to guess but everything is new. Any help would be great thanks

Update on this truck. After a week of driving I’d say the truck has the same issue..took it to shop and plugged into computer and found a engine speed derate. Cleared code and still no change. Installed new oversized injectors and took care of the low power issue(runs and pulls like it should now). Only problem is now after installing them I have a erratic idle. Everything is new on the truck except the lift pump could that be cause the rough idle?

Well after a few days of testing and diagnostics, I found a hole in my air line going to my boost gauge..fixed it and now I get 30lbs of boost under full load most of the time. Did not find any other leaks after pressurizing the intake system so I left the fresh air compressor pipe/hose alone for now. Truck still feels sluggish at times so I turned to the fuel system. Replaced all fuel lines, filters, and replaced check valve. While taking the line from the tank to filter housing off I found a chunk of plastic/rubber from the inside of the fuel line stuck in the elbow. Found my problem I’d say truck seems to run ok now. I may still check fuel pressure and replace the lift pump if need be when I get a few more days to mess with it. Was talking to a buddy that runs repair shop and he is seeing a lot of that from the fuel lines from trucks 20 years old or so. Thanks for all inputs everyone

Just did the intercooler. I can do that tonight, that should also tell me if my pipe for air intake on air compressor is good or not also ...how much pressure? 30lbs like the book says for the intercooler test?

Pressure check intercooler and found no leaks and it passed the leak down specs...so onto the air compressor intake pipe...plan to just use 3/4 inch hose to test it for a day and see what happens

Also note that when air compressor is pumping I lose 1 to 2 lbs of boost

Ya might be an option once I get the boost issue figured out...I did not pressure check it yet, also has 2 price manifold

Yesterday it seemed as air temps got warmer in the afternoon i was consistently lower on boost and ultimately power than in the morning....now this mornings ride to work the truck seems to be “normal” but still maximum of 24 lbs...just for the hell of it I took the check valve off on the return fuel side and inspected cleaned and put back in(didn’t find anything in there)...leaning towards changing the intercooler first before changing the cam gear since I was lower on boost before I didn’t the hp increase...t thanks for input!

Thanks everyone...So what is the process of changing the cam key?

Mack dealer put the request in to mack headquarters and never mentioned cam key...ran the truck all weekend here and temp didn’t move off of 180 all day...what does changing the key way do ? Change the timing I assume? What will it hurt if not changed? Also my problem with low boost was there before I upgraded the horsepower. Also truck is a 2000 amd I read somewhere you didn’t need to mess with key way in that year of truck but I don’t know for sure

Hello was wondering if I could pick your brain...recently took this truck from 350 to 427 using correct part numbers on the injectors and turbo , set the valves while is was there and had mack dealer reprogram Ecm. Truck has only 320000 actual miles on it...before it would only make 19 to 21 lbs of boost regularly. Now it only makes 20 to 22 lbs regularly. Truck runs ok but not a power house.. I feel like there is more power there by changing intercooler maybe? Or maybe cleaning a check valve ? Also last 6 of the vin 125886 maybe there’s a data file upgrade? thanks