1998 Buick Century Oil Pump

My Buick stalled out on me shortly before Christmas. I took it in and the guy has told me that the oil pump is bad and that would cost $800, but there had to be a reason why the pump went bad. He has no idea wht caused it. Is it worth puttign $800 into this car?

Right offhand, a '98 model car is worth fixing for 800 dollars (which sounds a bit high).
Before recommending that you wade into this I would want some more info.

You say the car “stalled out” on you. If the car stalled out because of a bad oil pump (chances of that, near zero) then the engine is junk.

Any red oil light come on? Is the engine full of oil? Any knocking, rattling, etc.? Has he performed an oil pressure test or what?
Just trying to figure out what’s going on here so you don’t spend 800 bucks and you are then told the motor is trashed.

You may want to check to see if your car has the kind of oil pressure sending unit that when it senses low oil pressure it disconnects the power to your fuel pump which in turn would cause the stalling. I know there are some cars that are setup like this just don’t know if yours is one of them.

Yes the red light came on twice over two weeks after I had an oil change. The light had come on before and I took it in and all it was, was a loose cap. So I figured it was probably the same thing till it stalled out. There was no sounds or the engine making anything nose or shaking. I drove it like always when it just stopped. It has started up since then but doesn’t stay started. We know it is the oil pump, but something had to cause it to go bad. Any ideas?

Yeah someone did suggest looking at the fuel pump but it is clear that the oil pump is bad.

You say the car “stalled out” on you. If the car stalled out because of a bad oil pump (chances of that, near zero) then the engine is junk.

SOME GM vehicles had the fuel pump connected through the oil sending unit, so if there was no oil preasure the fuel flow would kick off. I have no idea if this is the case with this car.

That still doesn’t explain the bad oil pump. The mechanic I took it to said I could go ahead and fix that bu tthere is no guarantee the car will be fixed.

Not trying to be contentious, but why is it clear it’s the oil pump? As ok4450 stated, if the engine stalled because of a failed oil pump, the engine is most likely a large boat anchor at this point.

I believe the red light to which you are referring is the “check engine” light, not the oil light. If the oil light never came on, it casts further doubt on the oil pump diagnosis.

No it was the oil light not the engine light that came on.

Some GMs did have a system that required sufficient oil pressure to enable the fuel pump circuitry. If yours is one, that would explain the stalling. The only other way a loss of oil pressure would stall an engine is if the parts actually bound up (seized) due to a lack of lubrication, and on that case the engine would be toast.

However, the reason everyone is wondering is that it’s rare for an oil pump to wear out. There are other more likely causes for loss of oil pressure. A plugged screen at the end of the “pickup” tube is one. It’s also possible that the pressure sensor is bad and the loss of signal caused the fuel pump to be disabled (if, in fact, you have that earlier described system). Like others, I’m skeptical of the diagnosis.

What exactly did the mechanc do to diagnose a bad oil pump?

He said that he was going to drop the oil pan.

This one may not have a happy ending. I asked if the engine oil level was fine and no answer.
The oil light came on several times and the cause was a “loose cap”. Not. There is no loose cap that has an affect on oil pressure unless a filler cap was left off and the engine lost a lot of oil which could then lead to a ruined engine. As far as tightening any kind of cap to make the oil light go out - no way.

Why does a mechanic have to drop the pan to inspect an oil pump. He does not.
Just how is it “known” the oil pump is bad?
If the oil light was on and the oil pump has legitimately failed (still near zero on the odds) then the engine is damaged.

At this point the entire story sounds disjointed and I sincerely hope that 800 bucks later the OP is not sitting there with a bad engine that has a new oil pump or a good engine/new pump that won’t start because of a fuel or ignition problem.

That still doesn’t explain the bad oil pump. The mechanic I took it to said I could go ahead and fix that bu tthere is no guarantee the car will be fixed.

Point I’m trying to make…is that if the fuel pump DOESN’T get it’s power from the oil sending unit…then I’d pretty much gurantee you the engine is toaste.

Me too. I find myself wondering if the proposal is to lift the engine, drop the pan, and check the pickup. $800 sounds like a lot of moola.

Do you, OK, know if this engine would have to be lifted to drop the pan?
Does anyone out there know if this vehicle has the fuel pump shutoff system that would justify this?


I pulled up the wiring diagram for the car and it shows power to the fuel pump is provided from the fuel pump relay. The fuel pump relay is controlled by the ECM. The ECM however does recieve a signal from the oil pressure switch. So in theory if the ECM recieved a signal showing a loss of oil pressure it could shut the car off.

As far as removing the oil pan:

To Remove:
Disconnect the negative battery cable.
Remove the engine mount struts from the engine.
Install an engine support fixture on the top of the engine
Safely raise and support the vehicle.
Remove the A/C compressor and secure it out of the way. It is not necessary to recover the refrigerant.
Disconnect the catalytic converter pipe from the right exhaust manifold.
Drain the engine oil.
Disconnect the oil level sensor connector.
Remove the starter motor.
Remove the transaxle brace from the oil pan.
Loosen the transaxle mount lower nuts.
Remove the engine mount lower nuts.
Lower the vehicle.
Raise the engine slightly with the engine support fixture.
Raise and safely support the vehicle.
Remove the engine mount bracket with mount from the oil pan.
Disconnect the right lower ball joint and outer tie rod from the steering knuckle.
Remove the bolts on the right side of the frame.
Loosen the bolts on the left side of the frame.
Remove the left and right oil pan side bolts.
Remove the oil pan retaining bolts.
Remove the oil pan and gasket.

According to my labor guide changing the oil pump is a 5.3 hour job.


The oil level was fine. The mechanic said he looked at the oil pump and it was bad.

The oil pump can fail from wear. How many miles on this beast? If it’s a very high-mileage car and the maintenance hasn’t been that great, the oil pump can certainly fail, or at least wear to the point where it’s not efficient enough to generate enough pressure in that tired old motor. Either way, if the mechanic has things torn apart enough to remove the old oil pump, you might as well have him put in a new one. The cost of the new pump will be the cheapest part of the whole operation.

I assume by this point the oil pump is out because of the “mechanic looked at the oil pump and it’s bad” remark.
The only additional remarks I will make at this point is that I’ve never seen a “bad” (as in completely failed) oil pump in my entire life and if for some fluky reason this pump is completely bad then one should assume the engine has damage due to the oil light coming on and the engine stalling.

Still wonderin’ if the oil light was flashing on due to an engine with an excessively low idle; possibly due to a failing fuel pump which could be the real reason behind the stalling.
Hopefully the OP will keep us informed on this.

I have seen 1 oil pump fail completely. It was an 84 Cad with the 4.1 v-8. The oil light never came on and the car was running when I shut it off. 2 hours later I went out to move it and it would not start. After doing some test I determined that the rotor was not turning. Didn’t crank like a broken timing chain so I pulled the distributor. As I suspected the drive gear was busted. Also the distributor drive rod was twisted. After removing the pan and oil pump I could not turn the pump. New oil pump, drive rod and distributor car run perfect. That was 5 years ago and still going strong.

Thanks Dartman. It’s all starting to make sense now.