Lack of power on 94 rv with 460 engine

Do a compression test. Maybe that motor needs major repair.

Did you replace the fuel filter? If not, you might want to. If you did replace it, make sure it is pointed in the right direction. Usually it will have an arrow pointing in the direction of the fuel flow.
Also was the fuel pump you installed an in tank pump or did you install an in line pump. If you installed an in line pump, it is important to locate it as close to the tank as possible, and make sure it is lower than the tank.

I'm not familiar with the vehicle (I write from the UK..) but yes sir, I would agree with you that it does sound like hot engine/fuel issues. Or maybe a 'cold start' injector, assuming it is a petrol engine.

I also agree that you don't throw money at it.

Personally, I would change the fuel filter (and air filter) anyway, it's the easiest and cheapest option.

You don't mention any problems when the vehicle is running, so I presume that when it is actually travelling, all is fine? If you had intermittent problems with the fuel pump I would have imagined that your vehicle would stall and splutter from time to time. Plus, at the low mileage you have done - a fuel pump shouldn't be failing or have problems.

I would change the fuel filter (and air filter if necessary) and also pour a can of 'injector cleaner' into the fuel tank as a 'lazy' or gummed-up injector(s) can cause starting problems - and take the vehicle for a nice fast run to 'try and clear things'.

Do the simple things first. The things YOU can do. With low mileage vehicles a 'glaze' can build up in the fuel system simply because the vehicle is low mileage /short runs. This causes injectors to become 'clogged and sticky'. Run it with additives in the fuel system ...

If all else fails, ask a workshop. But .. it sounds as though your vehicle is reliable apart from the starting-niggle. I don't think you have a big problem.

Probably a bad fuel pump. Verify power and ground arriving at the pump during cranking.

Sounds like an electrical problem(power to the fuel pump) change the fuel pump relay And make sure the roll over switch is not tripped, It is located behind the passenger side kick panel . The red button must be pressed in to reset.

Check your running fuel pump pressure. If (as I suspect) it's too low, first try changing your fuel filter. After changing the filter, recheck the running fuel pump pressure. If still low, check you fuel pump pressure regulator. If OK, you may need a new fuel pump.

Also probably would be a good idea to replace you air filter.

Good luck!

It sounds like you might have a clogged catalatic converter on the exhaust system.

Could they possibly have gotten the timing(check it with a light) off or distributor turned wrong? don-ohio

Sounds like it has a hard miss. Any engine codes? more info is needed there are a lot of things that could be wrong.

Sounds like the fuel supply pipe inside the fuel tank has hole that's why if the fuel level is about 1/4 and the pipe hole is not completely soak in the fuel, the fuel pump will sucks air instead of fuel and this can cause of lack of power first until the engine shut off but if your problem is sudden shut off without other symptoms like lack of power or engine rough running first before engine shutting off, most probably it was electical problem.