Chevrolet Repair: 5.7 vortec wont start cold, fuel pressure gauge, mass air flow sensor

Question
I have a 98 chevy c1500, 5.7 liter vortec that won't start after sitting all day and through the night. We have replaced the fuel pump, fuel pressure regulator, and tested fuel pressure. Once cranked, it runs like new and will start with the touch of the key as long as the engine is warm. When trying to crank, we can smell raw gas under the hood and from the exhaust, but the plugs are dry. We have found gas in the oil and the crankcase if full of gas fumes. The scan showed that the mass air flow sensor is bad, but I'm not convinced that this is the whole problem, since it runs so good when finally cranked. It is getting good fire and will hit occasionally when winding on the starter, but no crank.I suspect it has a leak in an injector line that is leaking fuel into the cylinders and crankcase. What are your thoughts?

Answer
HI MARK,THE WAY I UNDERSTAND YOUR QUESTION IS AFTER THE TRUCK SITS OVERNIGHT THERE IS A LONG ENG CRANK BEFORE IT STARTS UP !! I WILL AGREE WITH YOU ON YOUR LAST SENTENCE..THIS WILL TAKE SOME TIME TO DIAGNOSE BUT I THINK YOU ARE ON THE RIGHT TRACK..DO YOU HAVE A FUEL PRESSURE GAUGE AT YOUR HOUSE OR WAS THIS A SHOPS GAUGE ?? I WOULD LIKE YOU TO HOOK UP A UEL GAUGE AT NIGHT AND SEE WHAT THE PRESSURE IS WHEN IT IS RESTING [ENG OFF] REMEMBER THAT NUMBER WHEN YOU COME BACK OUT IN THE MORNING THE PRESSURE SHOULD ONLY DROP ABOUT 5 LBS. I SUSPECT THAT THE GAUGE WILL BE ON ZERO..NOW FOR THE FUN PART. YOU WILL NEED TO DIAGNOSE IF THIS IS A PCM [COMPUTER] OR INJECTOR BEING STUCK OPEN WHEN TURNED OFF. WE HAD AT OUR SHOP LAST YEAR THE SAME KIND OF TRUCK AND THE PCM WAS HOLDING 3  OF THE INJECTORS ON. WHICH WOULD EMPTY THE FUEL RAIL AND AND RESIDUAL PRESSURE IN THE SYSTEM..CAUSING LONG CRANK AFTER SITTING SEVERAL HOURS. FUEL IN THE OIL AND SO ON. TO CK LETS MAKE SURE FIRST THAT THE GAUGE DROPS TO ZERO AFTER SITTING.IF SO UNPLUG THE PCM OR REMOVE THE RELAY AND FUSE AT NIGHT AND SEE WHAT THE FUEL PRESSURE IS THE NEXT MORN. IF THE GAUGE IS STILL UP THERE [WITH PRESSURE] I WOULD SUSPECT A FAULTY PCM..IF THE GAUGE DROPS TO ZERO THEN WE HAVE A POSSIBLE INJ STUCK OPEN..BEING THAT THE ENG RUNS SO GOOD I FEEL IT IS A BAD PCM. BUT,,,YOU NEVER KNOW. MANY THINGS CAN CAUSE A FUEL INJ ENG TO RUN RICH BUT ONLY A FEW THINGS CAN CAUSE THIS TYPE OF PROBLEM...LET ME KNOW HOW YOU MAKE OUT TO THIS POINT AND GET BACK TO ME..GOOD LUCK TOM...