****Disclaimer This was orignally a post made to help trouble shoot another members car, as such there maybe steps that do not apply to you as well, it may not appear in complete logical order, and possibly has steps missing for your own problem.*****
1. Exhaust leak some where before turbo. (this used to happen to my K24 all the time, it got to the point where I actually tack welded the bolts into place after i got them tight Rolling Eyes ) This is really frusterating as a really small leak does a ton of boost damage. I found with mine I would still hit peak numbers at first but they would just take longer, and then slowly it would reduce the peak number and take longer to get to what ever peak it would hit. As well you will start to smoke alot more on the top end, where boost used to clean it up.
2. Boost leak some where. Though for the most part this "normally" tends to be an all or nothing deal not a slowly disindigrating problem. I.E. One pass you run 20psi then pop and you run like 5psi, but stranger things have happend.
I asume that you are using an adapter to run this turbo? My suggestion is start the car (preferably cold) put on some ear protection, have a buddy hold the rpm's steady at about 2000rpm grab a flashlight and a mirror and just your hands and start at the exhaust manifold feel and look around as much of it as possible, normally you can either feel or see an exhaust leak, if your not sure have your buddy "snap the throttle" a couple of times and I know that you are pushing enough fuel that you will get some black cloud coming out. Repeat this process untill you have gone over every pre-turbine exhaust connection.
If this is the case tighten it up and you should be good to go. If this is you also may need additional support for the turbo, heavy turbo's and some engine vibration have an amazing ability to loosen bolts, and most of the time they are the toughest one's to get at. :roll:
If that was your problem great if no exhaust leaks where found anywhere read on.
Added to orignal post
Wastegate diagnosis, this is a quick easyone, clamp the line from the turbo to the waste gate, or if it is a hardline the entire way just unplug it or undo it. Now go for a drive, Boost will be imidieatly known if that was the problem, if not read on. End Addition
The easiest way to diagnose a Boost leak is well with a boost gauge, now I assume you have one, and that it is tapped into the intake manifold or very near to it, this is perfect, now you need a second one. Go to Princess auto or napa or where ever and pic up a cheap airpressure gauge obviously you dont need anthing more then like a 0-30psi gauge.
(Aside: I know alot of guys that drag and pull frequently run two gauges full time just for troubleshooting and pressure loss sake, and boost gauge's are realitvly inexpensive so you may want to go this route.)
Now take and tap that gauge in right at the compressor or as close as you can get it. Run the gauge upto the cabin and go for a drive if there is any more then about a 3psi difference you have a boost leak. If there is any more then about a 1.5psi differance your intercooler and plumbing is lacking in efficiancy (the differnce will grow bigger with the more air you move through it.)
If you have the differnce you will have to go through the entire cold side and see where the leak is coming from, most bigger turbo's don't hardly spin if there is not any load as such having the car running and trying to feel the leak doesn't work for the cold side.
If this fix's your problem great! If not read on.
Now if when you did your road test looking for the differance across the gauges and they were about the same and both low, you may have a turbo problem. So with the Engine OFF take and pull off the intake look into the turbo is there any blades bent or missing is there any scoring on the compressor walls around the blades, finally what sorta play does the compressor have. There will be a little up and down, but should be none side to side. Finally spin the turbo by hand it should spin free without dragging. If still no problem is found then pull off the downpipe and look and the turbine wheel look for all of the same things as for the compressor.
If there is any damage to the turbo you probably found your problem, replace it or have it rebuilt. If this fix's it great! If not read on.
We have now looked at all of the boost system, at this point we have to assume that it is either an engine problem or a fuel problem so what we do now is grab our compression testor and do a compression test on the engine, if that is good acording to bently spec (iirc about 495psi for a new motor, down to about 400psi for a worn out one, if I am wrong please feel free to correct me with the right numbers. :wink: ) if your numbers are low it is rebuild time if they are fine then read on.
Now we can only asume at this point that it is a fuel problem as we have covered the "Air" section, and the "Heat" section so all we are left with is "Fuel + Timing" lucky for us on a diesel these go hand in hand.
So first thing drain the water seperater and if the fuel filter is at all old replace, check all lines for wear and bubbles that could be air leaks, if the system looks good all the way to the IP we can then assume that it is the IP or the injector's so first pull the injector's have them flow tested or just replace, if this solves it great! If not, it is the IP, as such you will have to remove and send it in for repair, or take the car to a place that will remove it and repair it. If this solves your problem Great! If not...
You are over my head it is time to spend some money on a diesel mechanic. :wink:
Topic: Lack of Boost Trouble Shooting. (Read 7304 times)
