Air hose to engine-DD 8V71 Turbo/Blower

I'm wondering what the air hose from the in cab air block/manifold (located on the dog house under the right side of dash) to the engine is for and where on the engine dose this hose connect to? I'm trying to track down a power loss. I think and hope its the left side bank of injectors N70's. Back to the hose. I found it attached to the front air box cover, left bank drain/breather nipple. I removed this hose and place another with a drain bottle Why would a air hose be attached here and run to the air manifold? I checked a Service Manual and It shows a air line from the manifold to the engine. But dose not explain where on the engine it attaches. I have a 1969 White Freight liner. DD 8V71 turbo/blower, 13sp Eaton Fullerton. I also tested the injectors with a 1/2" x 18" pipe. I used the tip of the pipe to press down on top of the injectors to simulate a miss fire. Right bank will drop RPM's, but the left bank three back will not and the front will a little.

 

Longhood379,
Thanks for the reply. I have the newer spring loaded racks (arms are spring loaded). I tried moving the rack on each head and get a change in rpms. I also used a temp gun and notice a big difference in the exhaust temps on the left bank. The right bank is in the 159-163deg rang and the left is 117-121deg range. I started up the truck and tried all the different checks, Johnson bar, breaks, parking brakes. There's no air comming out the hose ( just oil resedual ). This hose was traced to the left bank air box cover and attached to the cover. I removed and replaced with drain hose and bottle. I would like to find a good manual that would go over all the timing, injector ( have the tool ), racking, gov't,etc.... I haven't had my head under the hood on one of these engine for a long time

 

Hi-Stranger, No. There's no white smoke on start up. It's a single stack. Ok that's an idea on the fuel line. Now to find It in a COE. Is there a real way to make sure the injectors are good or bad. I worked on my cummins and crack the fuel lines to check if RPM's drop or not. I have a video up on youtube under TheWaterman1000 that show me running the truck. Also shows the air line.

 

Stanger,
I found the engine number after you mentioned the differnt valve cover. Here's the number 8VA-1337 5or6 4 then under it is another number 7087-7040. I'll check the fuel lines when the weather lets up a bit. I did check fuel pressure at the secondary filter housing and it reg's 65psi at around 2,100-2,900 RPM's. I did notice there are no check valves on the drain outlet from the air box and engine block, hummm. Wondering if the two on the left side are letting to much air box pressure out.