Oldsmobile/Buick Repair: Fuel pump problems, oil pressure switch, engine oil pressure

Question
Van, Before the pump went my car started right away. After I got the car back, was when the problem with it draining my battery started. When I would shut the car off, I would hear the pump run for a few seconds. For the heck of it I restarted the car a few minutes later. The battery was already struggling. Then a few days later the car struggled to start, but finally did. It was just like when the initial problem with the fuel pump, the only differance was it finally started. I took it right in at that time. I will talk to him tomorrow. Any other suggestions? Thanks so much! Laurie
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Followup To

Question -
My 92 olds bravada's fuel pump went. After replacing it with a new one it is draining my battery. My mechanic then replaced the relay. It is still running my new battery down to zero. My mechanic does not think the fuel pump is the problem. I DO! She started with no problem what so ever before the fuel pump went. HELP ME! Please!!!

Answer -
Hello Laurie,
If the fuel pump seems to be trying to run with the switch off, that might be what ruined your orriginal pump, and will ruin this one.
But even if the other pump was bad, it may not have been the pumps problem.
In addition to the relay for the pump, there is an oil pressure switch that supplies power to the pump as long as the engine oil pressure is above 4 PSI. Doesn't matter weather the key is on or off, or even if the relay is removed. It powers directly from the battery.
If that oil pressure switch is stuck closed, the pump will have power, but you may not hear it running, especially if it is barely making contact. But it will ruin the pump before long.

Get him to check that.

Van

Answer
Hi again Laurie,
A few seconds of the pump running could easily be attributed to the oil pressure switch operating it while the oil pressure drains off, and I can't see that short period drawing the battery down any more than operating the cigarette lighter for that period of time.

The true test will be to see if ALL voltage to the pump stops when that switch opens.

A good battery shouldn't pull down that quickly without some large load on it, which should be detectable with a basic battery drain test with a test light.

Here is a thought...if the injectors are dirty, that residual fuel pressure from the shutdown, could be dumping gas into the cylinders, causing a flooded condition.
That, of course, would only explain a hard start immediately after shutdown, and not the next morning.....just a thought.

Van