truck wont start

I have a 95 ram that won't start. When i turn the key over to start it, there is a spark at the positive terminal on the battery and i lose power (dome lights, ignition etc.). If i move the positive cable at the battery, i regain power again. Any suggestions on what the problem could be would be appreciated.

You have a bad battery connection that can destroy the sensitive electronics of your truck $$$$$.
Remove the battery cables, clean them and the battery terminals with a steel or brass brush until they're shiny clean then reinstall them.

I've cleaned the posts on the battery and it's made no difference.

What about the cable end?
If the cable itself is loose at the cable end, a replacement end will need to be acquired.
The cable will need to be cut from the old end, cable insulation trimmed and installed at the new end.

If the spark is at or sort of under the battery post, the post itself may be broken.
The battery will likely need to be replaced.
Most chain type auto parts stores do free battery checks in hope of earning your patronage. I'd give them that chance.

Sounds like your cable is bad or your battery has an internal short.

thanks for the help

I put a new battery in and that seems to have cured the problem. However, I have developed a new problem that i need help with. The truck is refusing to start again. It isn't getting any fuel or spark. When I turn the key over, the ignition coil and injectors only get power for about 3 seconds and that's it. when I try to start the engine, there's no power to the coil or injectors. I have a code that comes up; 12 problem with battery connection. direct battery input to pcm disconnected within the last 50 ignition key-on cycles. any advice would be greatly appreciated.

Check the fuel pump & ignition breakers in the power panel under the hood.
See if they're getting hot.

I checked them and they're not getting hot.

Do other electrical devices work, like the headlamps & horn?

yes everything else works (lights horn radio). It seems to be only ignition and fuel that are affected.

I'm starting to suspect the crankshaft position sensor...it tells the computer the engine is running, it won't provide spark or fuel to an engine that is turned off.
Is the Check Engine light on?
You may need to borrow a scan tool to see what the computer thinks.

Yep, CPS is probably the problem.