Low Boost

[KallyI]

This is going to be a bit long, I fear. I've had gauges for boost, EGT, and Tranny temp for about 5 years now, and I put an after (inter) cooler on about the same time, and I replaced the injectors about 8,000 miles ago, and installed the DSG timing gear set, as well as a Fluidampr harmonic balancer. The Vacuum pump was replaced about 8,000 miles ago, and the replacement is still pulling 20" at the wastegate solenoid. I replace that piece last summer.

I bought a Boost Fooler from Kennedy, as well as a reflashed PCM, designed to go with the Boost Fooler. It all worked quite well until last August, coming back from Missoula, Montana. With all the changes, I was running at 13 to 15 pounds of boost, and the EGT's were about 900°F to 1200°F, when pulling my 5th wheel, depending on the terrain. At some point on the trip home last summer, the boost dropped to a maximum of 10 pounds, and it will not go over that, no matter what I do. The truck does not pull the 5th wheel as well anymore.

I have checked all the tubing, clamp connections, and the cooler for leakage, as well as the intake, and can't find any signs of a leak. I do believe the pressure showing on my gauge.

About a month ago, I got the P0251 code, and the truck would not stay running, so I changed the pump. It had about 120,000 miles on it, so it wasn't necessarily a premature replacement. I thought perhaps this might fix the issue with boost, but it wasn't so.

At this point, I am at a loss what to do next. I have tried wiring the wastegate shut, and it made no difference. Could it be the turbine? The wheel spins freely, makes no abnormal noises, and looks good to my relatively inexperienced eye.

Any help or suggestions would be welcomed.

[ronniejoe]

Check for wear on the waste gate pivot shaft. If the bushing is worn, it can bind and prevent the waste gate from closing all the way. This happened to my truck back when it still had the factory turbo on it, interestingly enough, on the way to Missoula, Montana.

[KallyI]

Check for wear on the waste gate pivot shaft. If the bushing is worn, it can bind and prevent the waste gate from closing all the way. This happened to my truck back when it still had the factory turbo on it, interestingly enough, on the way to Missoula, Montana.

Thanks for the tip. I'll check it Saturday. Could a bad boost sensor create the condition? I ask, because I believe the boost sensor may not be working.

[ronniejoe]

The fact that you tried tying it closed suggests not. A mechanical problem with the pivot shaft could prevent closure even when wired "closed".

[Kennedy]

I'd like some clarification as to:

reflashed PCM, designed to go with the Boost Fooler

My programming works without the need for boost foolers.

What brand gauge do you have and what PSI range? My guess is Auto Meter 30 psi...

On edit now that I see the signature part 1 is confirmed. Try a different gauge. When I see issues like this they often trace back to errant Auto Meter gauges.

[suburbanK-2500HD]

Hi, i have been thinking about installing a intercooler on my truck also.
Do you have any pics of your setup.
What kind of cooler did you use.?

Thanks

Børge


This is going to be a bit long, I fear. I've had gauges for boost, EGT, and Tranny temp for about 5 years now, and I put an after (inter) cooler on about the same time, and I replaced the injectors about 8,000 miles ago, and installed the DSG timing gear set, as well as a Fluidampr harmonic balancer. The Vacuum pump was replaced about 8,000 miles ago, and the replacement is still pulling 20" at the wastegate solenoid. I replace that piece last summer.

I bought a Boost Fooler from Kennedy, as well as a reflashed PCM, designed to go with the Boost Fooler. It all worked quite well until last August, coming back from Missoula, Montana. With all the changes, I was running at 13 to 15 pounds of boost, and the EGT's were about 900°F to 1200°F, when pulling my 5th wheel, depending on the terrain. At some point on the trip home last summer, the boost dropped to a maximum of 10 pounds, and it will not go over that, no matter what I do. The truck does not pull the 5th wheel as well anymore.

I have checked all the tubing, clamp connections, and the cooler for leakage, as well as the intake, and can't find any signs of a leak. I do believe the pressure showing on my gauge.

About a month ago, I got the P0251 code, and the truck would not stay running, so I changed the pump. It had about 120,000 miles on it, so it wasn't necessarily a premature replacement. I thought perhaps this might fix the issue with boost, but it wasn't so.

At this point, I am at a loss what to do next. I have tried wiring the wastegate shut, and it made no difference. Could it be the turbine? The wheel spins freely, makes no abnormal noises, and looks good to my relatively inexperienced eye.

Any help or suggestions would be welcomed.

[KallyI]

I'd like some clarification as to:

reflashed PCM, designed to go with the Boost Fooler

My programming works without the need for boost foolers.

What brand gauge do you have and what PSI range? My guess is Auto Meter 30 psi...

On edit now that I see the signature part 1 is confirmed. Try a different gauge. When I see issues like this they often trace back to errant Auto Meter gauges.

I bought the boost fooler, and the PCM from you. I was not aware the PCM did not require the fooler.

You may well be right about the gauge, but the truck is still not pulling as well as it did before this all started. It is pulling about the same as before any changes were made on the engine, which is why I believe the gauge. I can try a different gauge and find out for sure.

[KallyI]

Hi, i have been thinking about installing a intercooler on my truck also.
Do you have any pics of your setup.
What kind of cooler did you use.?

Thanks

Børge


I don't have any pictures of the cooler setup. right now. I bought a cooler from ebay, that I felt would fit under the front. It's aluminum, with a 2.5" inlet and outlet. I'll see if I can get some pictures of the setup, and post them here.

[suburbanK-2500HD]

Thanks

that would be great..:)


I don't have any pictures of the cooler setup. right now. I bought a cooler from ebay, that I felt would fit under the front. It's aluminum, with a 2.5" inlet and outlet. I'll see if I can get some pictures of the setup, and post them here.

[JohnC]

How's the air filter look? What about the fuel filter? Any chance the inlet hose is getting sucked shut? Blockage in the intercooler? ...

[KallyI]

How's the air filter look? What about the fuel filter? Any chance the inlet hose is getting sucked shut? Blockage in the intercooler? ...

Air filter has 2000 miles on it, all on pavement, fuel filter was replaced last week. I haven't checked the intercooler for blockage inside the intercooler. I will, but after working for 4 years, I don't know what could have gotten into it.

[KallyI]

I checked the wastegate, and it has full movement, with no binding at any point.

The intercooler is free, and not blocked.

[Kennedy]

A good pressure test of the IC and plumbing including the boost gauge would be a good idea.

[stezloco]

if your 'intercooler' was holed at all...you'd hear it...squealling or whooshing sound (more than is usual) when flooring it....having it under the front puts it in line for a lot of stone damage....you say youve checked the 'turbine'??? i'm guessing you mean the inlet of the compressor wheel (alloy) the turbine wheel is on the 'hot end' and requires that you remove the turbo for a physical check of that part.....you can also have a good look at the wastegate disc itself for bits breaking off or a burnt seat area....(if youre running loaded /hot/high pyro temps regularly)
theres always Occams (Achems) Razor ...the theory that the simplest thing is usually at fault...start off with the easy and cheap checks first before writing off the big money items..theres some good suggestions here already listed by others....helps if you've got a bud with the same truck to swap/try expensive components..... good luck.;)