Ok, heres the deal

Have an 01 Cummins 6 speed with AFE air intake, 4" straight pipe and Van Aaken box.

Used to run 32 lbs of boost and spool fast.

Now I am only spooling 15-20 lbs. 15 lbs at lower RPM, 20 at higher RPM.

I used to be able to lug it in third and put it to the floor and get a small cloud of smoke. Nothing any more. No smoke at all.

When you have a boost leak shouldn't you get more black smoke?

I have the wastegate blocked with the little the 90 with the allen screw in it.

I replaced the drivers side intercooler boot. Replaced gauge line. Tightened clamps.

Did my box die or is it a leak somewere. Do these sound like stock #s for boost?

I was towing about a 5000 lb trailer up Bozeman pass(6000 ft or so) last night and could only spool about 15 lbs of boost at about 1800 RPM and 70-75 MPH(35s with 3.55s) with it on the floor. Still held about 75 MPH but only 15 lbs? EGTs with the pedal on the floor only hit 1050-1100 degrees.

Boost leak? Box die? Wastegate stuck open?

I guess I need to make a tester to check for leaks, but I was under the impression I would get more smoke with a boost leak.

Thanks

 

I had a simular problem and found by accident the wastegate had come unhooked.
Have a look at your wastegate.
good luck
scotte

 

From what you have described, it would appear most certain, that you are now fueling less than before and the issue is not a boost leak. The combination of factors: low boost, no smoke, low EGT's all point to less fuel, there is no doubt about that.

I am very sorry to say, that it sounds like you may have a dying VP there or perhaps just a dead lift pump. Because even if your box died, the Mach 1.6's should fuel harder than what you describe, I would think.

First things first, check your lift pump/fuel pressure. If that checks out ok, you might be loosing your VP.

A quick easy check is to take out the box and see if it changes. If it stays the same, then maybe in fact the box is dead. If if gets much better, than obviously the box is seriously hosed, but I have never heard of this happening.

Did this happen all of a sudden or over time?


KP

 

It happened sometime in November, but I don't know when. It was cold and the roads were snowy and I did not put my foot into it for a couple weeks. Then I did and noticed the low boost.

I don't have the injectors, but I want to get them.

I have the engine warranty till July as I only have 41,000 miles on the clock. Had a new lift pump in July or August of 05.

Have a fuel pressure gauge(mechanical) but has been unhooked because I cannot find anything that won't leak. I guess I could just hook it up again just to see.

 

whoops, I missed that 'some day' part.

Well in that case, yes it could indeed be only just the box. Unplug it and see what happens.

KP

 

Will give it a shot. Will pull the box and see what it does.

Even with a dead lift pump(only 10 PSI at idle) and could pull it zero wide open I still would get 32 lbs of boost before.

Although, shouldn't it stock, with the wastegate blocked still spool over 20 lbs? Or does the computer limit it?

 

Remember that the turbo is an exhaust-powered turbine driving an air compressor. It takes power to drive that compressor to make boost, and it takes hot exhaust to drive that turbine. With less fuel, you have cooler and less total exhaust available to drive that turbine, so it cant spin the compressor fast enough to make lots of boost.

short version: it takes fuel to make boost.



KP

 

your lack of smoke is from no boost , if your intake manifold sensor doesnt see any boost or lack of boost , the ECM will keep the IP from feeding it more fuel. I would be looking at what your boost signal is reading or if you have any boost leaks, boots or intercooler leaks.

 

Thanks John

Good info there

I will keep looking for boost leaks.

I will have to make the PVC tester.

I might also just plug the turbo with a pipe plug and cap off the wastegate to make sure that isn't the problem.

 

You might want to check to line to your guage to see if it is cracked. If I understand you correctly you are not complaining about power, only low boost reading? I would think that if your boost were that far down from normal you would have smoke anad power issues.

 

Brand new line to gauge

Don't have anything to compare the power too

 

Ok, put a 4" PVC fitting in and put about 10 lbs of pressure in

Took a couple of minutes to leak out. Using the soapy water I could not find any leaks.

The only air I felt leaking out was out of my boost elbow(90 with the set screw). There is a small hole in it that looks like its supposed to be there. But air comes out of it like crazy, even with only a few PSI.

Put in the stock elbow thing and will try a pipe plug and putting a screw and hose clamp on the other end tomarrow.

Will see what it does with the stock elbow as well.

 

This is what I would have expected.

And the boost elbow is supposed to leak off air through that hole, thats how it works.

You need to be looking at fuel.


KP

 

You haven't mentioned one crucial thing:

Does the truck seem to have less power? It should seem like it.

I'm no surprised that you aren't finding a boost leak. You probably aren't making the boost to begin with (as opposed to losing boost you had made).

1) Verify WG function with compressed air
2) Change Fuel Filter
3) Consider replacing MAP sensor

jmo

 

I don't know, its hard to tell. Seems like it doesn't pull as hard as before. Definitely doesn't seem to spool as fast either.

With the wastegate hooked up I am only getting 10-11 lbs of boost.

So this must mean a boost leak, correct?

Will the map sensor cause low boost? Trying a new one is not a problem as I work at an auto parts store. Also, would having the boost fooler of my VanAaken stop the check engine light from coming on if the sensor was bad?

It will actually spit a little cloud of black smoke when lugged in 3rd. So it seems like it fueling.

How do I verify the wastegate is working with compressed air? Just put 20 lbs in?

Fuel filter is new. Gauge line is new. Replaced drivers side lower boot.