6v92 low on power

gear jammer · September 09, 2021, 10:54:27 AM

Just got back from a 7000 mile excursion. 6v92 ddec 2 ran great. Used 1gallon of oil total. Has 80k miles total. In the last leg of the trip, 250 miles. It Was running good before this. Didn't notice it on the highway but after I stopped in Tucson for lunch. It was having a hard time getting going. Have a scan gauge and the boost is around 17-18,prior to this I have seen 28, usually you can feel the turbo kick in and pull before it shifts in 1st gear. it has always pushed some black smoke on take off. Now it's worse. This all being said I said it ran great before. It did to what I'm used to. But I always felt it could take off better from a stop. I have changed all fuel filters air filter. Checked fuel pressure at 75 against the governor no load. And no smoke no load. I pulled the intake tube and it he was turbo spins free, bearings feel okay. Hope someone can help. This all happened over the course of 250 miles so seems like something happened.

luvrbus · September 09, 2021, 11:00:05 AM

There are 2 -1/4 inch dia rubber hoses that attach to the turbo boost sensor one of those could have cracked ,broken or fell off check those as you aware the DDEC will only allow enough fuel as the air ratio dictates smart little joker isn't it

gear jammer · September 09, 2021, 12:52:42 PM

Thanks for the reply
Where is the boost sensor.
Thanks steve

luvrbus · September 09, 2021, 01:20:55 PM

Quote from: gear jammer on September 09, 2021, 12:52:42 PM
Thanks for the reply
Where is the boost sensor.
Thanks steve

Should be mounted on the end of the blower with a bracket

gear jammer · September 09, 2021, 03:00:51 PM

Okay I found it. The line looks okay. Without taking it off it's hard to tell. By the time I get it off I'm sure it will crack. Looks like special tubing? How about the blower bypass valve could that cause a problem. Or the air box drain check valves?
Steve

luvrbus · September 09, 2021, 03:37:02 PM

Quote from: gear jammer on September 09, 2021, 03:00:51 PM
Okay I found it. The line looks okay. Without taking it off it's hard to tell. By the time I get it off I'm sure it will crack. Looks like special tubing? How about the blower bypass valve could that cause a problem. Or the air box drain check valves?
Steve

The bypass has a hose too (silicone ) it opens when the turbo reaches more psi than the blower then the blower free wheels sorta of ,1 bolt and you can remove it clean it and try it,it is probably going to the boost sensor the connection could be corroded and not sending info to ECM.something else you need to check is be sure the fuse going to each cylinder bank hasn't blown and you are not running on 1 bank

gear jammer · September 09, 2021, 03:40:14 PM

I'll check and clean both. Replace the hoses. Anybody know the the part number for a boost sensor
Only going to do this once... I hope
Steve

gear jammer · September 09, 2021, 04:04:06 PM

Correct me if I'm wrong. On the blower bypass valve, vacuum should pull the plunger up?
I have it out and cleaned it not sure how it works.
Steve

gear jammer · September 09, 2021, 05:15:13 PM

Huh, where would I find the fuse for each cylinder bank?
Steve

luvrbus · September 09, 2021, 05:15:52 PM

Quote from: gear jammer on September 09, 2021, 04:04:06 PM
Correct me if I'm wrong. On the blower bypass valve, vacuum should pull the plunger up?
I have it out and cleaned it not sure how it works.
Steve

There is no vacuum on a Detroit air pressure opens the by pass on the blower around 5 or 6 lbs so the blower and turbo are about equal on pressure ,if the bypass slides freely it is good

luvrbus · September 09, 2021, 05:22:56 PM

Quote from: gear jammer on September 09, 2021, 05:15:13 PM
Huh, where would I find the fuse for each cylinder bank?
Steve

What bus do you have ? you can check for 1 side not firing with IR thermometer or by hand it has a fuse some place for each bank

gear jammer · September 09, 2021, 05:43:35 PM

Okay bypass is free. I'll check to see if both banks are hot, no corrosion at boost sensor. If the sensor was bad wouldn't it throw a code? It's a gillig bus chassis, 1994 country coach

luvrbus · September 09, 2021, 06:16:03 PM

Quote from: gear jammer on September 09, 2021, 05:43:35 PM
Okay bypass is free. I'll check to see if both banks are hot, no corrosion at boost sensor. If the sensor was bad wouldn't it throw a code? It's a gillig bus chassis, 1994 country coach

Not if the hose is broken lol another Country Coach owner I own a Magna 630 with the ISX 15 Cummins

gear jammer · September 09, 2021, 07:50:16 PM

Magna, beautiful coach, mines a concept. 36 foot. Love the thing.
Both banks are firing.

luvrbus · September 09, 2021, 08:10:46 PM

Quote from: gear jammer on September 09, 2021, 07:50:16 PM
Magna, beautiful coach, mines a concept. 36 foot. Love the thing.
Both banks are firing.

Ok behind the pulley that says 6v92 check and clean the connector to the timing sensor those are bad about breaking.I love my Magna too lol even if the guys here call it a sticks and stable job I am not giving it up