Detroit 12.7 DDEC 4 Interesting problem

Checked air compressor intake hose. It's fine. New boost sensor. Fuel mileage is varying. Pull it hard in the wind, it's down to 5. Decent load no wind. 7. Still no engine light. Sheesh. Stupid thing. Going to run it until something shows up that's a definite problem.

 

http://www.dieselenginetrader.com/diesel_talk/categories.cfm?catid=9
You should post over here too, I haven't been on there for a while but they used to have some pretty sharp detroit experts.

 

Do you have a pyro/EGT gauge?

 

I have a pyrometer. EGTs running normal. With the bigger Borg Warner turbo, they actually are about 150 degrees cooler than when using the factory Garrett turbo.

 

So you're getting air then, and if you were constantly losing 8-10 psi, you'd hear that for sure. If you just weren't pulling enough air, you're pyro would be higher. I'm guessing bad fuel lines as the next culprit. Do they appear original?

 

They are original. Thats my weekend project. Going to check them all and see what's up with them.

 

I have a '96 9400 12.7 with same issue. Have you found the fix yet? I still looking.

 

most likely electric . A freind of mine with EU truck ( mb actross) had a lot of trouble in what seem similar to your case,spent tons of $ changing mechanical parts . anyhow he found a sensor near the top of the engine near the turbo that was bad but went un-noticed to pc scan tool or dash. Warning

 

Hey guys. Still haven't figured it out. Just installed a manual boost gauge this weekend. Going to see if the computer is reading the manifold pressure right. As soon as I figure out the problem I will post it.

 

DO make sure you check ALL the parameters in the ECM. Just because the HP setting was flashed doesn't mean anything else was changed from prior settings.
While this sounds like a harness problem I would check to see if you're getting any air in the fuel lines.