How much is a new sump pump? If this is a full submersible, get a complete new pump and don’t fool around with replacing the capacitor for safety’s sake. You want a complete watertight unit.
Oil in the water can indicate a shaft seal failure on a sealed submersible. Repair is not practical except at a shop with a high dollar pump.
The only thing we ever bothered with changing run capacitors on have been blower motors, compressors, etc..
JMHO.
“...get a complete new pump and don’t fool around with replacing the capacitor for safety’s sake.”
Smart call. If OP is not married and lives alone, gopher it! Otherwise, face the music when it fails. You will be blamed by the wifey for trying to go cheap when it fails, even if over the normal operating lifetime. Just buy a new pump! It’s worth the extra cost in the long run.
There’s no oil in the water. Just INSIDE the housing. The seal is in great condition & should go back together fine. The intent is to see if I can put in a more reliable cap.
I have lots of experience with air-tight and also gas (natural and propane) tight. Plus some experience with submersible pumps. So long as corrosion / deterioration of surfaces / materials is not a problem (they look great), water tight is much easier. The oddities with the motor cap are a bit new to me though. Usually the failures are more obvious / drastic.
That said, I’ll set the reassembled pump in several feet of water for several days & then put it in a large bucket & test it. Moisture inside should trip the GFCI outlet.
I’m going to get a new pump anyway. But I suspect “skimping” on the caps happens on all but the most pricey. Motor caps seem to fail often. This is more of an engineering project to see if I can improve the thing, and will give me a backup.....
(Yeah, there’s already a “battery backup” pump installed, too.)
Just go to Tractor Service Center and they will match your old sump pump for half what Lowes, HD or other big box stores will sell it to you for. It costs about $75-150 for an electrician to wire it you are still lost.