Hey all, first question... I am not getting much boost. If I push it really hard going up on onramp, I can get maybe 11psi, usually only around 8psi ( I even bought a new gauge to make sure it wasn't bogus). We built one of the pressure tester deals that you hook up to the turbo (got the idea here I believe) and it doesn't appear to have any leaks, and that's even at 20psi with the tester. I turned up the star wheel 1/3 turn, spun the diaphram 90 deg., and put the smoke screw in 2 turns. But still only getting 8-11psi max. My brother gets almost 20psi. So, any ideas? Thanks in advance!

 

when was the last time the overhead was ran on the truck? if you can't recall, then i'd suggest that. look or listen for exhaust leaks around the manifold, and does it smoke like a rich dark black? or start out black and slightly grey up? also check endplay and radial play in the turbo... shouldn't have any end play (shucking back and forwarth) and radial (up and down) i haven't seen a turbo w/o any so as long as it doesnt rub the housing your ok. then of course the obvious... air filter and fuel filter restrictions... gotta have air and fuel to create the gasses to push the turbo, if ya arent pushin the turbo go back to the basics, air, fuel, heat... and idk how common the intake gasket goes out on the first gens, but that could be the cause of a massive boost leak, and if the intercooler checked out, take a close look at the boost boots and make sure there arent any leaks there either.

 

This may sound ignorant, but what is overhead? Does that mean adjusting the valves? I installed a new fuel filter, and the air filter is good. We ran the pressure tester and it held 20psi pretty solid. I'll try and check the exhaust manifold for leaks.

 

yeah, the overhead is a valve adjustment. sorry, different people call it different things. but i'd look at the source (exhaust) and the supply to the engine (intake) for leaks... cummins intakes are 2 pieces with a bolt on top, possible leak there could cause a massive leak and in turn, low boost. look for clean spots where everything else around is dirty the pressurized air will actually clean the leaking area over time. typically just small straigh lines with a slight fan spread at the end.

 

are you running a factory turbo or a wastegated turbo off a later model. i dont know for sure but it is possible that the waste gate is screwed up

 

waste gate.... hmmm didnt think of that, assumed it was a non waste gated turbo being a first gen, even then didnt think of someone putting one on. good point cumminskid

 

It is a non-wastegated first gen. Ok, I've been watching closely while driving. I notice when I'm on it, at around 2200rpm I'm getting some grey smoke out the pipe. Also, I notice my boost falls off really quick right around 2600rpm. The truck seems to lose power when it's fully warmed up and doesn't boost up as well. I'm going to check the valves this weekend and see what I see. Oh, also, I didn't see any clean spots around the intake manifold....

 

At 2600 the it is defueling thats why the boost is falling off there but you should still be seeing around 18 psi or so the rest of the time.

 

18psi easily... how restrictive is your exhaust? if back pressure is equal to drive pressure then you arent going to be getting anywhere very fast at all... and idk how probable it is either; but broken fins on the turbine wheel? has anyone heard of this by chance? i do know that it'd keep the exhaust from pushing like it should. but fins dont just break unless they're making contact with something. so we're back to when i asked earlier about the condition of the turbo... any play to speak of? and have you replaced the fuel filter?

 

you want to turn down the star wheel, not up.... that is delaying full fueling. Turn, the fuel cone to the deepest setting, and bottom out the full power screw to the collar. that should give you the boost you are looking for.