Morbark 17 Cummins 4bt has Vacuum?? Need Causes!!

[GarethVW]

My cummins 4bt has 10 psi of vacuum at idle and doesn't really change when I rev it up. The injection pump was recently rebuilt and the turbo was replaced with a good used one. I am kind of at a loss the only other thing I can come up with is burnt valves. (Air back feeding through the intake slows down the turbo so it wont spool) Any ideas?

 

[jrr344]

Where are you taking your reading at?

 

[GarethVW]

I removed a plug on the manifold right by where the fuel lines come around from the injection pump

 

[jrr344]

Have you inspected the intake boots between the turbo and intake, and make sure that the turbo is functional by pulling the air filter intake boot and make sure it will turn and is not hitting or come apart? Also make sure you have no exhaust leaks before the turbo and your waste gate is stuck open.

 

[GarethVW]

All that seems fine I just replaced the turbo with a good used one and the intake and exhaust seem fine

 

[Biker Dude]

Vacuum at idle would be normal but as it revs up you should see it switch to pressure and increase. The wastegate controls the boost pressure so you may want to look there. There should be a little hose that runs from the turbo to the wastegate actuator. That hose is where I usually take my boost pressure reading from. Also, just free revving the engine won't produce much boost, maybe 3-5 psi. You have to put the engine under a load to get a true boost reading.

 

[GarethVW]

Well, I figured it out. I didn't know that I had an air to water intercooler in the intake manifold, and when I took the intake apart I could see the fins were clogged up with oily gunk. I cleaned it out and am back in buisness!!

 

[046]

diesels can't generate vacuum except with a vacuum pump.
you've got a separate vacuum pump driven by the 4BT

The vacuum pump is mounted on the timing gear case. There is a gear in the Cummins timing gear case that is attached to the vacuum pump.

My cummins 4bt has 10 psi of vacuum at idle and doesn't really change when I rev it up. The injection pump was recently rebuilt and the turbo was replaced with a good used one. I am kind of at a loss the only other thing I can come up with is burnt valves. (Air back feeding through the intake slows down the turbo so it wont spool) Any ideas?