Return filter got dirty on a ruud achiever super quiet 80 and pilot light on heater will not ignite

You need to clean the pilot its blocked when it burns yellow .No heat in it.

going out on safety. either high limit or failure to detect flame.

Ignitor is probably too fare up. Adjust it lower !

The most common things that will cause a system to freeze up are:
1. Dirty air filters
2. Dirty evaporator coil
3. Indoor fan motor not running
4. Blocked/restricted return air flow
5. Low on refrigerant charge ( most common)

I would start with the filters. When the system is froze up, turn off the "cool" and just have the fan set to on. Make sure there is no more ice anywhere, turn the system back on and check your air flow throughout the house. If it feels normal, then filters, return, and fan should be good. The outside unit will have warm to hot air coming out of the fan if the charge is good enough, but that's not a perfect way to check, you will need gauges and a temp reader with knowledge of super-heat and sub-cooling to check the charge the right way. Hope this helps and good luck!

so with the door over the blower compartment it wont run? Does it blow the flames out?

I would try to check your return air first, making sure there is no blockage and that your air filters are clean. It almost sounds like when you take the cover off, you are pulling enough air into the system for it to run, but as soon as you close it off, it's not getting enough air flow, therefore, tripping a limit switch inside the furnace. Most furnaces will also have the codes for the flashing lights and what they mean on the inside of the door covers.

cannot vent horizontally, need to install b-vent and go up

http://www.ruudac.com/products/ProductInfo.aspx?XSL_File=ruudac_products.xsl&Market=Residential&SectionVar=Heating&Category=Oil%20Furnaces
Go to this web site and check out you specific unit. should have users manual. Hope this helps

the flame sensor is dirty.