have a 97 fl60 with a 5.9/allison 4spd.went camping last weekend and had about 40 miles on it.was driving down the road doing about 55-60 and all the sudden the turbo whistle increased about half again what it was.this lasted til i came to the next stop sign and took off again,then i didn't really notice it.fast forward to today.i fired it up in the campground to come home,it idled for about 5 minutes before we left,then it was about a half mile to the road at 10-15 mph.temp at this point is about 140 or so.when i get to the main road and take off i get up to 55 or so just driving along and the turbo does it again.it has a more distinct whistle then (normal).but one thing i noticed is it sure runs alot better when it's louder.when it's quiet it seems to really work to get 60mph,but when it's louder i barely have to press the pedal to maintain 60mph.one other thing i noticed.this thing has always had a ticking to it,and i have isolated it to the fuel line out of the tank to the lift pump,grab the hose and you can feel every tick.with the turbo louder the tick also seems louder.does this sound like a lift pump issue??plugged filter??turbo going south??

 

Do you have gauges? if so whats your boost at? possible waste gate not opening? Whats your fuel pressure at? Only suggestion i can make is if you dont have gauges you should get some. They will help you diagnose possible problems.

 

no i don't have them yet,well actually i have a pyro and boost,but they are in another vehicle right now.and i have been thinking about a fuel pressure gauge.

 

I can't explain the increase in power, but maybe the noise is a cracked high pressure intake boot. As for the ticking, many owners have tried to fix it by replacing the overflow valve, without sucess. I believe the current thinking is the ticking is caused by a worn lift pump. Do a search.

 

well today i got the hood popped open and checked the diaphram on the wastegate.i could not for the life of me get it to move.i put vacuum to the diaphram and pushed on the lever and it will not move whatsoever.how easy should they move???this thing came out of minnesota and the outside of the exhaust side of the turbo looks like its about to rust thru.i'm thinking maybe the wastegate is sticking or stuck altogether.i had the intake hose off the front and the turbo feels nice and tight and spins freely.

 

update:got my boost and pyro mounted and took it out for a spin today.took off and i was running about 4 lbs of boost and about 600 degrees when it hit second,the boost went up to about 8 lbs and temp about 800,then hit 3rd boost went to about 10 and temp to 1000,then 4th and boost hit about 14 or so and temp up to 1200,by the time i got up to 55 the temp and boost came down.cruising on a level the boost was about 5-7 and temp 850-950.do these numbers sound about right or should i have more boost and lower temps??i did change the fuel filter and it seems my ticking is not as loud as before.i still need a fuel pressure gauge.hopefully within the next week or so.

 

The Cummins system uses Boost pressure to control Boost level, unlike the GM system with a vacuum-controlled wg - the wg is stiffly spring loaded, so you will likely not be able to open it by hand - Boost pressure on the wg diaphragm aids exhaust pressure on the 'gate to open the wg at ~12psi - block the line at the wg actuator for ~25psi Boost - keep a close watch on EGT at those levels of Boost.

Your current Boost readings are good, but do not indicate your original symptoms - keep an eye on the guages, post results when that happens

 

i'll try blocking that line.but first i think i'm gonna add a fuel pressure gauge.