Cat 977H with 3306 SN 3N917 - Question about air line for scroll style fuel pump

Greetings,

I have been having issues with backfiring and popping from this engine. I determined that the backfiring and popping was isolated to cylinder 3 by cracking each fuel line. The popping and backfiring stopped when the fuel line for cylinder 3 was cracked. I took off the scroll style fuel pump and brought it up to the local diesel shop that my Cat dealer sends older fuel pumps to. As soon as I placed it on the counter they noticed that I had oil leaking out of the tube shown in the bottom left of the attached picture. I explained that an oil line had been hooked up there. They informed me that this wasn't right and that an air line should go there. This actually explains a lot. This engine has been spattering oil out of the exhaust. Someone had branched off a t-connector from the oil line that feeds into the oil pressure gauge on the dash. I am going to cap that off. My question is.. can anyone tell me where the other end of the air line goes? I have looked over the service manual and parts manuals and don't see this illustrated anywhere. Any help would be greatly appreciated!

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That is a fuel ratio control it should be hooked to the intake on the head
Is this the motor out of a tractor.
Usually a loader doesn't have one.
Bob

Hi Bob, yes the motor came out of a D7F. Should I just cap it off at the pump in the spot shown in the picture? Curious, why do dozers have the fuel ratio control and loaders dont?

Because tractors have a decelerator, used to hold down excessive black smoke.
ask the fuel shop if they can remove it. and make sure they know it's for a loader.
Bob

Will do, thanks Bob!

Later loaders have a fuel air ratio controller. It's an air pollution thing to cut down on black smoke when varying engine load.