Cadillac Repair: does my cadillac need a new motor, negative battery cable, pressure relief valve

Question
i have a 1987 cadillac deville. initially my car cut off after being driven for 10-15 minutes.  i had a new battery installed, oil changed and radiator repaired, fuel filter replaced and water pump replaced.  still after driving less than 2 blocks the car will cut off after driving for this period.  i was told by a mechanic that the car was losing oil pressure and that my car now needed another motor.  please help/advise if this is possible because the mechanic that has done all of the above mentioned repairs is suggeting a
new motor . this is a 1987 cadillac deville  

Answer
Hi Tiffany, Too bad the mechanic didn't suggest the engine before all the work was done. It sounds like you could have several issues going on here.
The oil pressure needs to get addressed first and a mechanical pressue gage needs to get hooked up and see what kind of pressure there is. The caddys run real low pressures somewhere around 8psi at idle in drive is still considered ok. If the oil light is on or came on after the oil change then the oil pump is to blame. I have seen a couple of times where the pressure relief valve comes out of the pump after the lof and replaceing the pump gets everything alright again. The o-ring on the pump pick-up tube has a tendency ot get hard and crack and that will cause low pressure also. If you have 125,000 miles or more the bearings might just be worn out. One time I had to disassemble an engine that someone had put a pump in and found a worn middle camshaft bearing and that was what caused the loss of oil pressure. At that point it was engine time because Cadillac doesn't recommend replacing the cam bearings.
As for the engine quits issue you need to determine if the engine is loosing fuel or spark. On a vehicle as old as this it could be a bad fuel pump, ignition module inside the distributor or a poor ground where the negative battery cable attaches to the engine block near the starter. That is where I would start. The computor could have a bad soldier joint inside and replaceing it might keep the engine running. Sounds like you need someone that is well versed with the caddy to diagnose it. Let me know if you need more help. Bill