Having some issues on a Cat 3406E 6TS with air in the return line to tanks. Think it’s something that has very slowly getting worse. Had a long block installed in Jan 2019. Ran silky smooth from out of the shop. Little over a month goes by develops a slight miss, lope, whump whump on what sounds like cylinder/injector issues. Truck shook at idle. Took back to shop, told me sounds normal. I’m thinking no it ran better and something changed. On and off for years now been running about the same. Fuel mileage has been 5-6.5. I haul grain local. Miles could be 5-150 loaded, idle time 5 minutes to hours. Stop and go, hard acceleration, etc. figure 5-6.5mpg is acceptable and not shabby for 90k# loads.
Sorry for the history and dragging it out, but feel it’s relavent to the issue. Last year I install a non waste gate turbo. Took power to a whole better level. I run a tune on this truck for 600hp and 2000’# tq. So the guy told me. Always questioned the stock filter setup if it would flow adequately to feed it. I don’t have a fass or air dog. Just stock cat pump.
Here’s the issue that has come up. Boost last year would go to at least 35psi if not 40psi if pushed. Back then it was steady on the needle. Now it fluctuates severely(10psi). Starts around 10 all the way to 35psi. Hard to make 35psi now. Bout a month ago it was cutting out entirely. Even had one morning sounded like a injector failing to fire. Cleared up after a minute or so. Engine even was cutting out one day hauling down the road. Babied it back 40 miles. So I replaced my primary water/separates filter(Baldwin Bf1259). Found the drain plug barely seated. Ok air getting in from there, seemed all well. Cutting out down the road happens again. Replaced it with a Cat 256-8753 about 2-3 weeks later. Checked it’s drain, loose. Tightened figured all’s well. Few days ago, cutting out yet again! This time I’m trying a (Baldwin BF7557) as I had air in my return line(had sight glasses installed now for about 1-2 months). Today I ran diagnosis on the system. Also installed a vacuum gauge to see filter restriction(.5-1”hg of vac currently). With a sight on the suction and tank return line off the filter base this is what I came up with. No bubbles at all from the sight glass on the suction side. These figures were tested at operational temp(185-190*).
-Idle; slight lope in exhaust, 85-90psi with a 2-5psi erratic flutter, no bubbles in return.
-1200; smooth 100psi, slight bubbles starting/pulse.
-1600; rough running, 105psi, pulse of bubbles(almost foamy looking)
-1800; rough running(same as 1600), 110psi a lot more pulsing bubbles
-2100; less rough than 1600-1800rpm. 115-120psi. Lesser bubbles then 1800rpm.
I also check with a temp gun(I question it and need to get another to verify), but the steel portion of the return line before pressure regulator in filter base read around 115*. The brass sight glass after the regulator was 130*. Doesn’t seem right. Again I’m gonna get another temp gun to check. Fuel level I was lower(40 gallons left in tanks). I did check in tanks and fuel was flowing back very well to both sides. Did see some grey film on the sides near the level of fuel. Never had this before. Might be something to mess the filter up?
What should fuel pressures be? Is there a way to find out off the regulator that’s in the filter housing? Also the secondary filter base is the newer style for the C15’s think part number was 136-5017 that I installed. Cat pump came over at the long block install. So did injectors. Injectors were installed bout 6 months prior to the long block. Might have 150,000 miles on them.
Not sure what to check anymore. Had replaced quite a few things over the time. Just got used to it, figured it was the best it was going to run. But something now is getting worse and the mechanics around hear aren’t sure what it is? Kind of alone on this one. I have more details on what other things have been replaced or not, but I made this entirely too long already, again sorry for that. Hoping someone out there had similar issues and can point me in the right path. Thank You so much in advance!