Do what rasmataz suggested.
If it switches off like a light (instantly), then it is loss of spark. Loss of fuel pressure would cause the engine to slowly die-out.
Crankshaft or camshaft position sensor sensor could cause immediate stalling (switching off), as would a faulty ECM Power
What size engine (or engine code) are you dealing with.
Sunday, October 28th, 2012 AT 5:29 AM