I believe Ford moved the Computer to the upper center of the firewall in the early 2000's.
It's connector could get moisture inside from water coming down thru the hood gasket.
They added a cover to this connector at some point because of problems with water getting inside.
Just to take it off the table as a possible cause I would unhook the battery and then remove the connector to see if it shows signs of moisture damage inside.
I would also get a can of Starting Fluid(ether) and next time you get a no start, remove PCV hose or Power Brake hose from intake manifold, spray some fluid in and replace hose.
Now crank engine, if it doesn't fire then spark is turned off for some reason.
If it fires and then dies, fuel is cut off.
This is a 50/50 test and will save you time pin pointing a problem
Not sure if the 2005 Ranger has an anti-theft system, I thought PATS was discontinued in Rangers in '04.
But if you have one and theft light is flashing then that would be the problem, water is getting in somewhere and causing alarm to cause a no start
Last edited by RonD; 01-04-2015 at 09:58 AM.