Vacuum Question...............

[Badazz chevy]

Ok I'm still learning about diesel engines here...lol.
I don't think i am getting much or any boost. thing runs great empty, till i start up a hill with weight behind me. Starts blowin out black smoke then drops a gear and goes to a grawl. i'm talking about maybe 5k . so...until my gauge gets here and i install it, i've been playing with the turbo. i notice theres NO vacuum at the wastegate and the lever is down. i raced the motor up a few times and the lever went up and stayed there. at idle ......it was still there till i pulled the vacuum line off, then the lever went back down. Is this normal ? when the wastegate is closed? (up or down).......where should the lever be ? if this is NOT right...whats the problem ?

Its a 1998 k3500 4x4 1 ton dually
new injection pump and relocated PMD

Thanks Jeff

 

[JMJNet]

Get a vacuum gauge and make sure you get vacuum from the vacuum pump plus there is no leak on the line.

 

[Badazz chevy]

Why would the wastegate be holding vacuum ? it pulls the arm...but doesn't seem to let go . soon as i pull the line (vacuum),the arms drops back down? i'm guessin, the vacuum pulls the arm to drop boost. well why doesn't it return when i go back to an idle?

 

[Badazz chevy]

I just bought a boost gauge...just have to find time to pull intake off to mount plug for boost gauge.
:thumbsup:

 

[buddy]

The wastegate without vacuum will just swing open, the vacuum sucks the diaphragm in and pulls the lever closed and holds it closed. To build boost you need to hold the wastegate closed. At idle, the computer holds the wastegate fully closed until you have boost then it tries to regulate it by varrying vacuum to allow the wastegate open a little or a lot.

 

[WarWagon]

Any codes in the computer? Waste gate control via the solenoid, tubes and vac pump are the mechanical aspect of it and most prone to fail. So is a plugged air filter or plugged soot trap,(cat converter.)

Less common is the MAP sensor or other issues wigging out the computer.

Start with codes and then check airflow. Sounds like the vac system is sort of working. But check it again...

 

[silveradostew]

Simplest fix is to remove the vacuum part and make or buy the mechanical setup with the spring tension to hold the gate. Real easy to know what it's doing then. Once you get your gauge installed it's an easy job to set the tension on the spring to hold boost until you want it to dump.

 

[buddy]

If its just a vac line the easiest thing to do is repair it, even a new solenoid is simple and not expensive. It depends how you want it to perform, mine performed very well with the vacuum setup.

 

[Turbine Doc]

Vac system when working is fine, unfortunately as these trucks get older requires $$$ to keep up & running and been my luck 2x times leaves you stranded with a load on vehicle and inability for turbo assist. What I suspect Jeff is you have a partial leak at one of the solenoids, a weak vac pump, line leak or diphragm leak at the WG actuator on side of the turbo itself, or maybe even a exhaust leak not letting full drive exhaust to make it to the turbo.

You may want to spend some time in the TRL here http://www.thetruckstop.us/forum/showthread.php?589-6.5-Diesel-Technical-Library and here http://www.thetruckstop.us/forum/showthread.php?589-6.5-Diesel-Technical-Library to better understand the way it is supposed to function.

WG is supposed to be closed at all times fully unless PCM sees you making too much boost for what it has been programmed for then it opens the wg to bleed off drive energy to turbo ergo lessening boost. If there is a pre-existing vac/turbo issue this can lead to black smoke low power as the PCM is somewhat dumb to vac issues from a leak or insufficient vac supply. S L-56 EGR engines in OBD-II family monitor vac and will code with oddball vac problems though coding as a boost problem which drives one to start down the wrong path sometimes.