Turbo 101

[ranger71]

Hey guys quick question. So I’m dealing with a sluggish motor. I have a rebuild kit for the turbo, not really any forward and back play but enough top to bottom or side to side to touch the case if you nudge it that way. No contact with the housing as yet while running. Other thing is I tried manually pushing the actuator rod for the wastegate and it moves freely but just watched it while the motor revved up to 2500-3000 in neutral and it didn’t move at all. Thoughts? Bad turbo internals? Bad actuator? Both? Checked everywhere for boost leaks except the inter cooler itself. One other thing, I have a loss of prime issue going on overnight sometimes, 430k stock motor. All comments appreciated, sorry I can’t supply boost and fuel pressures as I don’t have any gauges for that, just hoping someone with working experience can help me narrow this down. No smoke issues at all, burning clean but only seems to boost in second gear (first and second) or if the truck is running flat or downhill, the smallest hill and it fails to rev past 1800-1900 and boost normally, hits around 2000 historically. I’ve owned this truck for 18 years and want it happy again with your help!

 

[GAmes]

You won't develop enough boost in neutral to activate the actuator. The factory service manual gives instructions of checking/adjusting it using shop air. Lots of people rebuild their own turbos. A key part of the process is to index the wheels to the shaft, they spin at 25,000+ rpm so balance is key. Personally I just replace mine. You have got your money out of it at 430k. I like this one. http://www.pdrdiesel.com/products/PDR_Diesel_HX35_Turbo-481-139.html The founder of Piers Diesel was a member of the TDR years ago.

Losing prime is normally an air leak between the fuel tank and the lift pump. Once again, shop air regulated to about 15 psi. Pressurize the tank using a rag or a fuel cap rigged with a shrader valve and check the lines for air bubbles. I'll save you the effort to use the search function. https://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html

 

[ofelas]

In the same vein as the excellent PDR HX35 hybrid, I'll go one step further & say you can re-use your existing turbine housing & wastegate on the new assembly.

Theres also an option for a factory replacement here, complete with housing/wastegate - https://shop.dieseltuff.com/Turbos-Accessories_c224.htm

 

[KATOOM]

Hey guys quick question. So I’m dealing with a sluggish motor. I have a rebuild kit for the turbo, not really any forward and back play but enough top to bottom or side to side to touch the case if you nudge it that way. No contact with the housing as yet while running. Other thing is I tried manually pushing the actuator rod for the wastegate and it moves freely but just watched it while the motor revved up to 2500-3000 in neutral and it didn’t move at all. Thoughts? Bad turbo internals? Bad actuator? Both? Checked everywhere for boost leaks except the inter cooler itself. One other thing, I have a loss of prime issue going on overnight sometimes, 430k stock motor. All comments appreciated, sorry I can’t supply boost and fuel pressures as I don’t have any gauges for that, just hoping someone with working experience can help me narrow this down. No smoke issues at all, burning clean but only seems to boost in second gear (first and second) or if the truck is running flat or downhill, the smallest hill and it fails to rev past 1800-1900 and boost normally, hits around 2000 historically. I’ve owned this truck for 18 years and want it happy again with your help!

Turbo's dont build boost just by free revving the engine so you wont discover anything by trying that. I'm not really sure what you mean by "sluggish" either since thats a very general statement. Maybe this acceleration chart will help you understand how your truck compares to what baseline should be fore a stock truck: http://dodgeram.info/tsb/1999/18-21-99.htm

Since you dont have any gauges to help diagnose whats you think could possibly be going on, most suggestions will be shooting in the dark. So I'd say that unless your turbo whistle sounds different than before then the turbo is likely fine.
What you could be experiencing though is some basic maintenance issues like a clogged fuel filter, valves in desperate need of adjustment, or simply a tired automatic transmission torque converter that cant hold back the old Cummins like it used to.

 

[DavidC]

So what year are we talking about ? Some truck specific's would be nice. First thing to change is the fuel filter