Engine/Transmission (1998.5 - 2002) How do you check the wastegate actuator ?

[SMalafy]

I am having excessive fuel consumption on my 01 and was looking at the wastegate actuator as being the problem. I do not see any vacuum lines running to it only a steel line going to the front of the turbo. I see the 2 mount bolts for the actuator and I wanted to know how I can check it ?

 

[petersonj]

The wastegate actuator is in part is a diaphragm that receives boost pressure from the compressor side of the turbo. That pressure puts force on the diaphragm which is connected to a rod and a valve inside the exhaust side of the turbo. When that valve opens, some of the exhaust is diverted away from the turbine wheel. This sets boost at a maximum psi.

Is there a specific reason you are focusing on the wastegate? Do you have an operational boost gauge?

Is your engine an SO or HO? The wastegate opens at a lower pressure on a standard output engine - around 22 psi boost for SO and around 26 psi boost for HO. These boost pressures will be attained while the engine is under a significant load at 1800 rpms or higher.

If you can reach the pressure rated for your engine (and the pressure doesn't continue climbing), then I would say the wastegate is functioning properly.

- John

 

[SMalafy]

The wastegate actuator is in part is a diaphragm that receives boost pressure from the compressor side of the turbo. That pressure puts force on the diaphragm which is connected to a rod and a valve inside the exhaust side of the turbo. When that valve opens, some of the exhaust is diverted away from the turbine wheel. This sets boost at a maximum psi.

Is there a specific reason you are focusing on the wastegate? Do you have an operational boost gauge?

Is your engine an SO or HO? The wastegate opens at a lower pressure on a standard output engine - around 22 psi boost for SO and around 26 psi boost for HO. These boost pressures will be attained while the engine is under a significant load at 1800 rpms or higher.

If you can reach the pressure rated for your engine (and the pressure doesn't continue climbing), then I would say the wastegate is functioning properly.

- John

I have an SO and a boost gauge and I only get 7 PSI at top rpm

 

[petersonj]

Is it possible that your engine has gone into a de-rated mode (sometimes called limp mode)? Is the exhaust clear when you are at top rpm at 7 psi boost? If so, the ECM may be de-rating the engine for some reason.

Low boost doesn't mean that there is necessarily something wrong with the turbocharger or wastegate. If the ECM is not commanding full fuel when needed, then boost will be low since the turbocharger operation is dependent on exhaust gas flow to drive the turbine.

Your symptoms can be caused by many things. A blown intercooler hose could be dumping half the boost. A faulty MAP sensor or faulty associated wiring could cause a de-rate mode. Other sensors and wiring could be an issue. Usually, codes will be set.

Have you checked for trouble codes? If so, what are they?

More detail regarding the symptoms would be helpful, such as miles on the truck, work that has been done to the truck (what and when), etc.

- John

 

[GAmes]

I have an SO and a boost gauge and I only get 7 PSI at top rpm

Under what conditions? Under a load, like while pulling a trailer up a hill in drive or OD, or normal city driving?

 

[SMalafy]

Under what conditions? Under a load, like while pulling a trailer up a hill in drive or OD, or normal city driving?

Whether accelerating hard waiting for the gears to wind out and change or even going up a steep hill. Truck is empty almost all the time and no city driving. I am going out now to use my SMARTY to check the DTC codes again.

 

[SMalafy]

Is it possible that your engine has gone into a de-rated mode (sometimes called limp mode)? Is the exhaust clear when you are at top rpm at 7 psi boost? If so, the ECM may be de-rating the engine for some reason.

Low boost doesn't mean that there is necessarily something wrong with the turbocharger or wastegate. If the ECM is not commanding full fuel when needed, then boost will be low since the turbocharger operation is dependent on exhaust gas flow to drive the turbine.

Your symptoms can be caused by many things. A blown intercooler hose could be dumping half the boost. A faulty MAP sensor or faulty associated wiring could cause a de-rate mode. Other sensors and wiring could be an issue. Usually, codes will be set.

Have you checked for trouble codes? If so, what are they?

More detail regarding the symptoms would be helpful, such as miles on the truck, work that has been done to the truck (what and when), etc.

- John

Thanks for your suggestions. I went out to check the DTC codes and have 3 . The lift pump code which I ignored all of the time because I installed an Air Dog Raptor lift pump which they want you to run 16 to 17. 2 other codes were P1693 JTEC module which I do not know what that stands for and P0122 low throttle position sensor voltage whcih I do not know what would cause that. I also have a intercooler hose which seems like is broke or slipped 1/2 way off the pipe. At 258K I should probably buy the BD silicone ones and replace them all. Thanks for the feed back. I need to go find out if the intercooler hose just slipped or if it is torn. I guess I do not have to worry about the waste gate then.

 

[petersonj]

The P1693 is just a companion code that can appear when codes are set in either or both the ECM and PCM.

and P0122 low throttle position sensor voltage whcih I do not know what would cause that

A worn out APPS (accelerator pedal position sensor) can cause a de-rating of the engine. How many miles on the APPS?

Definitely check the condition of the intercooler hoses.

Clear the codes and see what comes back.

- John

 

[SMalafy]

The P1693 is just a companion code that can appear when codes are set in either or both the ECM and PCM.



A worn out APPS (accelerator pedal position sensor) can cause a de-rating of the engine. How many miles on the APPS?

Definitely check the condition of the intercooler hoses.

Clear the codes and see what comes back.

- John

Just changed it out last year with a Standard sensor

 

[gtwitch]

Interesting here as my 1999 2500 is doing some of the same things, sometimes I feel the boost come in and sometimes not , I changed out the APPS 19 or so years ago so I have not checked that. I had a mechanic tell me that it might be time for a new turbo, I guess I'll pull the air inlet and feel the turbo rotation with my fingers and also look at the Intercooler input and output also. Mine comes and goes with boost.
I did start by replaceing the filters, I have a frame mounted lift pump with a inline filter/water drain at the output of the pump and the stock filter up on the block above the starter. I found no signs of water in either filter. I was wondering if I should possibly check and or bleed the injector lines from the VP44 at the head??

 

[GAmes]

I had a mechanic tell me that it might be time for a new turbo,

Considering that stock turbos last 500k+ miles, I doubt it.

 

[gtwitch]

I rigged up a pressure regulator today and hooked up air pressure to the wastegate actuator and with a mirror placed where I can see the actuator linkage, it does not move with 30 psi on the actuator, this tells me that the actuator is faulty or the wastegate is stuck in some way.
Now my question is how do you get the actuator off to check and also Do I have to pull the Turbo to check the the freedom of the movement of the wastegate. Never had this problem, so any knowledge anyone can send my way will be appreciated.
gtwitch in wyoming

 

[GAmes]

On a 2WD the actuator can be replaced. I did it once but can't remember if I had to do part of the work from below or not. Taking the air filter out of the way might give you the room you need. Once the actuator is disconnected from the gate's arm it should move easily by hand.

 

[gtwitch]

after thinking about this issue , I hooked up the air to the actuator again and very quickly turned air off and on at 40 psi and I can now see the actuator rod and arm moving about 1/2 to 3/4 inch so it is working and while the air cleaner was still off, I started the engine and the turbo is turning at idle. So back together and test drive, Thanks to GA and after looking some more I can see how you can get the actuator removed from the turbo with not a lot of work.
gtwitch in wyoming

 

[gtwitch]

Back quickly here, I suppose that the spring in the actuator could be broken and could cause the wastegate to be dumping too much boost pressure and causing the issue of intermittently loosing power due to that and could the reason for the power coming and gong. I'll kmow more later today

 

[GAmes]

I've never had one apart but I don't think there is a spring in there. It is a bellows and only the preformed rubber makes it expand.

 

[petersonj]

I could be wrong here, but I think there is a heavy spring inside the wastegate actuator that holds the wastegate closed with a fair amount of force. That is why about 40 psi air pressure was needed to open the wastegate.

In real life operation, much less air pressure from the turbo is required because exhaust turbine pressure is being applied to the waste gate valve at the same time, thus assisting the boost pressure to open the waste gate. A 40 psi wastegate bench test could be the same as a 26 psi wastegate in real-life operation.

Photo of a typical wastegate actuator below.

- John

 

[gtwitch]

John:
OK thanks for the drawing, As I see this, as the boost comes up the actuator piston pushes the rod clevis to open the wastegate thus wasting turbo boost and as that happens , then the boost pressure is controlled so an over boost pressure condition dose not happen! It looks like there has to be a seal around the piston and if that seal is leaking , this might cause an over boost condition, however if the spring is weak /collapsed, the opposite could happen and a low boost pressure to the engine could cause the problem I am seeing. I have ordered an actuator and that looks like I can put that in without pulling the turbo off, the e-clip might be the real problem but we will see.
Thanks for the insight here
gtwitch in wyoming George

 

[petersonj]

The fact that you mention supplying 30 psi air to the boost actuator and the wastegate did not open, and then you applied 40 psi air and the wastegate did open indicates that the the wastegate is performing as it should and that the spring is strong - not broken.

Most turbo under-boost problems are related to clamps or hoses that are loose / torn on the pressure side, or that the engine is not getting enough fuel (can be many causes) to drive the turbo.

- John

 

[gtwitch]

John After changing the (both) fuel filters) I bled air at the forward fuel filter located in the stock location above the starter but did not crack and bleed the injector lines downstream at the head from the VP44, should I do this also?
gtwitch in wyomiing