Starts and then cuts right back off

My mini van will start but, cuts right back off. I got the van about eight months ago check engine light was on but, everything worked, except the radio. I put new spark plugs and wires in it. I checked all my fuse and replaced all. Radio was still out. A week after I got it the front passenger light went out. I replaced it. This would happen three more times. Then one day the front window shield wipers came on and staid on even when the switch was in the off position. Two weeks ago the speedometer stopped working now when will start and go right back off. The only way to keep her running is holding the key in cranked position. I need to get my van running again. Any thoughts?