wastegate problems

[gennylight01]

Truck throws a code 78. Replaced solenoid, cleared code and it came right back. I have 25" of vacuum at solenoid and at wastegate actuator. Any thoughts???

[Oldsmoke]

78 must code for other faults as well as low vacumn. Obviously your vacumn is not a problem. It is essential to have your scan interpreted by a mechanic with experience with these trucks.:)

[TedReminder]

Year of truck helps. I'm guessing 94-95.
With truck running, grab wastegate rod and see if it moves. It should be rock solid. If it moves and you do indeed have vacuum at the actuator, the actuator is probably bad, not holding vacuum.
Ted

[Oldsmoke]

I was going to add that in another post but he beat me to it.:)

[gennylight01]

Thanks guys. It is a 94 and I have a sheet with all codes. I will try that though.
Code 78 is specifically a wastegate solenoid problem which is why I replaced it.

[grancito]

I have posted a lot after code 78 that was not a wastegate problem. You need to install a turbo pressure gage, I found that the gage vibrated at 2500 rpm and above and the pressure dropped, that is valve problems, mine has lifter problems but broken springs or bad rockers will cause the same.

[Joe 94 dually]

What is an actuator and where is it and what does it look like? I thought I knew what most basic engine parts were, but apparently I know next to nothing about a diesel in a pick up. They say a little knowledge is dangerous, but I don't think I even qualify to be dangerous.

[hraney]

The actuator is a "can" either right under the turbo or right behind it. It has a rod that connects to a shaft that runs into the turbo close to the outlet. There is a vacuum line to the other end of the "can". I am in agreement w/ Grancito, you really need a boost gauge for definitive diagnosis.

[Joe 94 dually]

The actuator is a "can" either right under the turbo or right behind it. It has a rod that connects to a shaft that runs into the turbo close to the outlet. There is a vacuum line to the other end of the "can". I am in agreement w/ Grancito, you really need a boost gauge for definitive diagnosis.
The only "can" I see is next to the turbo on top of the pass. side valve cover. It goes into the valve cover and has a hose going to the air boot in front of the turbo, it also has a sticker on top of it that says this end up. Also, with the engine running, "wastegate rod" moves freely back and forth. I think I need to get a vacuum gauge and check at the wastegate solenoid, the vacuum pump and the actuator (if I'm identifying this correctly). Does this all sound correct?

[torque454]

Sounds right. The can on the valve cover that says "this end up" is the CDR valve. The actuator is the little canister on the end of the wastegate rod which you have found.

[Joe 94 dually]

O.K. thank you I got it now. The vacuum line that's attached to it was either already broke or I just broke it. It's dark out now and I can't tell where the other end of this tube goes to. I sure hope a new one is less brittle! But this would certainly seem to be a reason why it seems I'm getting nothing from the turbo.

[torque454]

Those are hard plastic lines. Replace them with rubber. That line comes from the vacuum solenoid on the drivers side valve cover back towards the back of the engine. It plunges off beneath the intake and snakes its way back to the back on the other side. From there it goes to the vacuum pump, which on my truck is on the passengers side at the bottom. Might be different on your truck, mines a 96 and they changed the location of the accessories in 95 i believe.

[gennylight01]

Thanks for the input. I can move that rod pretty easily with the truck running. I'm guessing the spring inside is broken. Where can I find a new one if I need it and what do they cost??

[hraney]

If you have no vacuum on the can, the rod will flop since vacuum holds it closed. So if the vac line is broken to it the spring is probably OK, just lack of vacuum.
Personally, I would opt for going w/ a manual controller instead of putting the factory vacuum controlled system back in service. If its old enough the lines are brittle and breaking, then the vac pump is probably not far behind (especially if its the original pump). It sure does make things simpler in my opinion. Plus, the cost of the TurboMaster is just a bit less than the cost of a new vac pump. I don't even know if you can buy the vacuum can separately.

[gennylight01]

I have 25" of vacuum going to it, 25" to solenoid, as well as power to solenoid which is why I think spring is broke. Can I get a turbomaster for a 1994????

[grancito]

Have you got vacuum to the waste gate can? If not, the solenoid is not working.

[hraney]

I have 25" of vacuum going to it, 25" to solenoid, as well as power to solenoid which is why I think spring is broke. Can I get a turbomaster for a 1994????

Is that 25" at the can? or coming out of the solenoid? I guess the wastegate itself could be gunked up and hung open. W/O going back through the entire subject, have we determined whether or not you can move the wastegate rod w/ the engine killed? Oops, I see now, that yes you can... Hmmmm... I bet its not the spring, but a hole in the diaphragm in the can.
And yes, the turbomaster is available for any turbo'd 6.5.

[Joe 94 dually]

I found that I have no vacuum going to the actuator "can". So yesterday, I safty wired the rod forward and took it for a little spin. I can definately hear the turbo spool up now. I didn't go at it too hard to be able to see how much of a performance improvment this makes, but it seems to be pretty big. Now, at least I know my turbo works. I ordered a turbo master and boost gauge on friday so I should be all set.

On that note, what is the easiest way to install the boost gauge at the turbo?

[grancito]

Remove the intake extension and drill an tap a hole somewhere in the top.

[AGNSCODY]

Remove the canister and the vacume pump. Or leave vacume pump as a pulley. Then install a spring to hold the wastegate shut. Also install a booste gauge so that you can adjust your booste. disconnect your batteries and leave them off for an hour or so, this usually earases the codes. Then try running it again. Thats what I did with the help from others here and I have not had any more problems with it. If you need some pictures E-mail me and I'll reply back with the pictures. I post them here but they are to large in file size and if I reduce the quality to fit, it makes it hard to understand. But I did the conversion for less than $5.00 in parts available at a local hardware store.

Steve Cody
Agnscody@aol.com
agnscody@sbcglobal.net