How to shut a 55 off every time I put it away and get it back out after a few weeks the battery is down.

Could be the battery. Jump it with another car and see if it stops. Ford put the security in the Instrument panel for a few years. This flickering could be the reason in shuts down after a couple seconds.

check the battery terminals and posts are shiny clean and tight. Check for loose wires and other terminals that may be dirty or loose.. Have the fault codes read

maybe but i dont think so, lost key coding woiuld allow to start fine and smooth and then shut down after a few sec. the best way to track this problem would be with a scan tool.
not sure what year or engine is in this nissan 55 plate but scanning for codes would be the best way to start

Some times the new part is bad. If you put the old one in do all the new symptoms go away if they do take the part back.

Jeeps have a known problem of a crank shaft position sensor going bad. It's a sensor that works off rotation of the crank. to know where and what position it's in. The part is about $55 and it's located by the front of the transmission where it meets the engine block. Very easy to change. I've changed a few on Jeeps and they had the same problem with the Jeep shutting down going down the road. After a few days to 2 weeks it will go completely out and leave you stranded. So I" advise to get it fixed ASAP. "Crank Shaft Position Sensor"

change engine on my 1.8d van after fitting the engine now the van wont crank over

never heard of any such problem, are u sure it is not just getting sludged up and sticking? Have you tried cleaning it 1st?, here is how u do that.
Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

foolow the instructions below, u have lost the idle learn, clean the ntake and then drive for a week or so. this will fix the problem.
Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Have you cycled key , on,off,on,off,on, leave on, & see if check engine light flashes out any codes? It will give a few quick flashes, then pause, then a few more flashes. For example: 3 flashes, pause, 3 more flashes, is code 33. 2 flashes, pause, 2 more, is code 22. Will always be in sets of 2 digits, then a little longer pause in between each. When you get 5, pause & 5 more, that's end of message code 55. Try it and get back to us. Have a pen & paper ready when you are ready.