Product Description
Cummins 3918428 — Engine Oil Pressure Regulator Plunger
MPN: 3918428 | Also Known As: oil pressure regulator plunger, pressure relief plunger | System: Lubrication (oil filter head/regulator)
Why This Part
- ✓ OE regulation of oil pressure to protect bearings, turbo, and valvetrain.
- ✓ Direct-fit for 1994–1998 Ram 5.9L 12-valve (verify by VIN/ESN).
- ✓ Hardened, wear-resistant plunger for consistent pressure control.
- ✓ Restores factory operation after wear, sticking, or contamination.
Quick Specs
| Type | Engine oil pressure regulator plunger |
|---|---|
| OE Part # | 3918428 |
| Mating Spring | 3918427 (compression/relief spring, sold separately) |
| Qty Required | 1 per engine (inspect spring & plug during service) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1994–1998 | Ram 5.9L 12-Valve (6BT/ISB) | Ram 2500/3500 |
Industrial/Off-Highway: Common across Cummins B-Series families, incl. 4B3.9 & 6B5.9 (check ESN for exact spec and year breakpoints).
Often Paired With
- Compression/Relief Spring: Cummins 3918427 (mates with this plunger)
- Oil Filter Housing / Head: Cummins 5289557
- Oil Cooler Gaskets (5.9L ’03–’07): 3864458 & 4895742
- Oil Cooler Gaskets (6.7L ’07.5+): 3974127 & 2830559
- Fresh oil & filter after any lubrication system work
What’s In The Box
- (1) Genuine Cummins Oil Pressure Regulator Plunger (3918428)
- Spring/plug/gaskets sold separately (see “Often Paired With”).
Install Tips
- Inspect bore for scoring; clean passages thoroughly.
- Replace companion spring (3918427) if worn or set.
- Prime system and check hot idle pressure after install.
FAQ
WILL THIS FIT MY 1994–1998 5.9L 12-VALVE RAM?Yes—this plunger is commonly used in the oil pressure regulator assembly on 1994–1998 5.9L 12-valve Ram trucks (verify by VIN/ESN and filter head casting).
IS THIS THE SAME AS THE 4BT/INDUSTRIAL B-SERIES PLUNGER?It’s the same OE number used across many B-Series applications, including 4B3.9 and 6B5.9 engines. Always confirm by ESN for industrial equipment.
DO I NEED THE SPRING TOO?We recommend inspecting/replacing the companion compression spring (Cummins 3918427) to ensure stable pressure.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 3918428 built to factory spec and surface finish.
WHAT SYMPTOMS POINT TO A WORN REGULATOR PLUNGER?Erratic oil pressure, delayed pressure build on cold start, or scoring/wear on the plunger/bore during inspection.
