• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Changed Vac pump, have suction @ turbo, no boost

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
Messages
4,838
Reaction score
846
Location
NW Kansas and SC Idaho
Hey guys, We changed the vac pump on my 96, and at idle, it will pull at my finger at both the solenoid and at the turbo, but with it on the road, she wont build boost.

I cannot move the arm at idle, so I feel the vac canister and lines are good.

Do I have the two plastic lines reversed at the solenoid?
 
Not to be mean or sound stupid, but can you move the waste gate arm while its NOT running??? My 93 builds LOT of boost, BUT I recently found out that the waste gate is frozen almost all the way shut....Hints it will make boost and yet dump some off BUT the wastegate dont work!!! I knew their was something up when a spring loaded gate wasnt tripping...Yours is vac but you might wanna check to see if its stuck!!!
 
Check the diaphragm on the actuator I had one that developed a slow leak that would close the WG at idle like it is supposed to put could not maintain sufficient vac on the diaphragm to keep WG shut at power. It only takes a slight crack of the WG bypass flapper to keep you from making boost.

Put a mitey vac or similar device to test the diaphragm, if that checks out okay, you'll need to install a vac gauge between the WG & WG solenoid to see if vac is falling off once you get the vac solenoid hot, also possibly a small vac leak that doesn't matter at idle, but matters at power.

best thing IMO junk the vac system, go TM if you want to maintain the GM turbo, or ultimate fix go ATT, "

Waste Gate ????? we don't need no steenking Waste Gate" :D
 
Last edited:
sears tractor fan, yes, I am able to freely move it around with the motor shut off.

supposedly the turbo was rebuilt shortly before i purchased the truck, but the vac canister does look original, so I doubt it was replaced. so the leak at the diaphragm is a possibility.

could the solenoid need changing?

If i cant figure this out soon, I am about to go turbo master. (as this truck isnt worthy of an ATT! :) )

Later Edit:

I do remember in our rush to get the truck together, we did use gas line, cause we were out of vac line on that short section from the pump to the plastic line. could the pump pull enough to collapse this?
 
Last edited:
You can put a pump on the wastegate actuator to see if you can move it. If not, then diaphragm is bad.
 
You must log in or register to reply here.
Back
Top