On the lionel fef and the real 844 there are two small exhaust stakes up by the smoke stacks. One is in the middle of the two stacks and the other one comes out of the square exhaust steam injector rectangular box. Are these also indicators the the injector is working or something else like air compressor exhaust.

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the other one comes out of the square exhaust steam injector rectangular box

Do you mean the feedwater heater?

I am not famililar with the UP 4-8-4s so somebody else who knows the specifics of the UP 4-8-4s will have to answer for certainty,
but I'd guess the larger one is the airpump exhaust and the smaller one is the feedwater pump exhaust. One could be the feedwater heater exhaust but that is usually returned to the tender as water.

Wyhog

There is NO "exhaust steam injector" on 844. The UP began converting the FEF class from the Sellers Exhaust Steam Injector to the Worthington SA Feedwater System, in the early/mid 1950s. The 844 has the Worthington SA system.

The two steam exhausts up around the stack housing are; 1) air pump exhausts and 2) the feedwater heating tank vent. Western railroads generally did NOT pipe any feedwater exhausts back to the tenders due to the severe cold weather (more potential to freeze something else). The Worthington feed pump (hot pump) exhaust is piped into the heater tank right along with cylinder exhaust steam. For what it is worth, SP4449 is the same way.