I'm using way more cleaning fluid

The cleaning solution tank is only sufficient for part of a room, unless the room is very small.

Are you following the instructions for using the cleaner carefully? The machine has to be pulled backwards (towards you) at a steady pace in order for the vacuum to pick up the water that is dispensed. Do not use it like a normal vacuum cleaner - that will not work.

You need to start facing a wall, and pull the cleaner towards you, moving at about one foot every two or three seconds. The vacuum will then pick up the water that has been dispensed and the carpet will be damp but not sodden.

I have a older mod. Bissell carpet machine plus mod. 1630-5 and need a floor nozzle part num.013-6194 and grip tube w/button part num.014-4181 and trigger part num.010-9406 and tube

You need to replace the pump belt. Here is the belt you need:

Bissell ProHeat Belt

the problem is the heater is cloged you can drill it out to clean it

Below is a link to dirt devil. just put in your model# for the manual.
However most cleaners you buy give you the cleaner to water ratio on the bottle. Also you do not need to use Dirt Devil cleaner. All carpet cleaning solution are pretty much the same aside from the fragrance. The best ratio that I have found is approximately 5oz of cleaner for every gallon of water. Make sure you use hot water. Using cold water or waiting to long to use the mixture can reduce the efficiency of the cleaner.
Hope this helps.

http://www.dirtdevil.com/CustomerService/Manuals/default.aspx?id=32173

Sounds like the valve at the bottom of the solution bottle needs replacement.

Hi. Try it just using cold water only. If this now flows ok the water you are putting in to tank is to hot causing pressure to build up in tank which which causes the plunger to not be able to push hard enough against valve in the tank.