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Fits the Cummins 6CT8.3 and L8.9 engines. This is the oil pump for those machines, replacing Cummins 3991123.
Cummins 3991123 is the engine oil pump: a cast iron body with a three hole mounting flange, a drive gear and a meshing idler gear. It is used on Cummins 6CT engines. This aftermarket version is made to the same mounting and connections as the original, so it fits where the old one came off.
The same part is also sold as Cummins 4941464.
Sold as one unit. Check the number on your old part, or in the parts manual for your machine, before ordering.
| Part Type | Oil Pump |
| Replaces | Cummins 4941464 |
| Engine | Cummins 6CT8.3 / L8.9 |
| Cross references | Cummins 3991123 |
| Fits | Cummins 6CT8.3, 6L and L8.9 engines, including the 6CT in Komatsu PC360-7 excavators |
| Condition | New, aftermarket |
| Stat. HS-Code | 841330 |
| Country of Manufacture | China |
Cummins machines
Check the part number on your old unit before ordering.
| Cummins Part No.(SPM Part No.) | Fits |
|---|---|
| 4941464(SPM-HEP-4571) | Cummins 6CT8.3, 6L and L8.9 engines, including the 6CT in Komatsu PC360-7 excavators |
| 3991123(SPM-HEP-4571) | Cummins 6CT8.3, 6L and L8.9 engines, including the 6CT in Komatsu PC360-7 excavators |
Low oil pressure
A warning light or low gauge reading with the right oil level and a good sender often means a worn oil pump.
Engine rebuilds
Fit a new oil pump whenever the engine is rebuilt or the bearings are changed. Worn gears undo a fresh rebuild.
Noise from the bottom end
Rattles at start-up while the pressure builds are a sign the pump is not priming quickly enough.
Fitting tips
Prime the pump with clean oil, fit new gaskets and O rings, and check the pickup screen before closing up.
We check what other aftermarket sellers charge for this same part. Their prices on the date we checked:
| Seller | Price | Checked |
|---|---|---|
| eBay (3 aftermarket sellers) | USD 78.99 to 85.45 | 30 Oct 2026 |
| FridayParts | USD 120.75 | 31 Oct 2026 |
| HeavyDutyKits (PAI) | USD 192.61 | 31 Oct 2026 |
| SINOCMP | USD 239.00 | 30 Oct 2026 |
| Spare Part Mart | USD 63.19 | Today |
Our price of USD 63.19 is 20% to 74% less than these sellers.
Found this part cheaper somewhere else? Send us the listing and we will beat it by 5% under our Price Beat Guarantee. Every order is also covered by our 30 day money back guarantee.
This one, the aftermarket replacement for Cummins 3991123. It also fits the L8.9 engines. Check the number on your old oil pump against the cross reference table before you order.
On the Cummins 6CT8.3, often 5,000 to 10,000 hours with clean fluid, much less with dirt or air in the system. It is usually changed on condition, not by hours.
Leaks from the seal or weep hole, noise or whining, overheating, or falling pressure or flow under load.
Clean them right back to metal and fit the new gasket or O-ring dry, unless the engine manual calls for sealant.
Most failures come from contamination, cavitation from a restricted inlet, or running low on fluid. Check the inlet and the fluid before fitting the new oil pump.
No. It is an aftermarket oil pump made to replace the Cummins 3991123. It is not made by the original manufacturer; the number only shows what it replaces.
Live rates for the quantity selected, delivered to your door. Confirmed at checkout.
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