Pontiac Repair: 1990 pontiac gran prix. 3.1 v6 vin t., pontiac gran prix, coolant temperature sensor

Question
QUESTION: why does fuel pump continue to run for approx. 30 secs after ign key is turned off and out of the ignition switch,flooding the engine. this only happens after car sits over night at first try to start.any insight would be appreciated.

ANSWER: Hi Mike.

Give me a bit more information. It floods the engine??? The pump can run for an hour but if the injectors are not turning on the engine will not flood out. when you shut off the engine can you hera the injectors still clicking away or anything else under the hood clicking or turning on and off? It could be a few things the fuel pump relay could be sticking on or the negine control computer could bee keeing the fule pump on along with other relays and solenoids. This is a very wierd issue and the more you can tell me what's going on I can try to give you a starting pint.


---------- FOLLOW-UP ----------

QUESTION: Hi Todd, I have some follow up info that might help.This problem started out as intermittent and seemed temperature related after sitting out overnight. here is the data, ignition on,then to start,I crank for approx 30 secs,no start.turn ign. off. pump continues to run for approx 30 secs.,no injector clicking noticed,only pump.After this happens,the only way to start is to bleed off fuel from pressure port on rail while someone else is cranking engine and i operate throttle valve,It then acts like it is getting enough air[clearing flood condition?]and starts but slowly [like mixture isnt correct.]After getting it started its usually good for the rest of the day.I have replaced the fuel press. regulator,fuel pump relay and coolant temperature sensor. also recieved a MAP sensor trouble code and that component was replaced. removed IAC and cleaned pintle and cavity. tried reset of TPS BY DISCONNECTING WITH KEY TO "on" THEN KEY "OFF"AND RECONNECTED PLUG.THIS THING IS DRIVING ME CRAZY . I appreciate your response and hope this sheds some more light on this problem.thanks in advance for any more help you can give me .  Mike

Answer
Wow this is wierd... If I rememebr correctly the pump does run for a split second after that car is shut off normally but not for 30 seconds... has any service engine light come on? that would be where I would start. If not then the next place I would go it to check all of the engine grounds make sure they are clean an tight. with the car running wiggle the wires by the engine control computer and ther  is a herness that runs under the radiator and ther is a dip in that harness on the right side pull on that and see if it acts up at all if it does your getting closer.. If not try this pay on the computer with the handle of a screwdriver and see if it stalls out or acts up if so the computer is bad.. Not scientific but effective.. That's really all I have for you. There are a few other ideas from left field but see if that helps any..\