Product Description
Cummins 3947799 — Fuel Rail Pressure Relief Valve (PRV)
MPN: 3947799 | Also Known As: rail pressure relief valve, pressure limiting valve | Cross-Refs: Bosch 1110010029, F00R00632 (for identification)
Why This Part
- ✓ Genuine OE PRV that maintains proper common-rail pressure and protects components.
- ✓ Direct-fit for 2003–2007 Ram 5.9L ISB (24V common-rail).
- ✓ Restores factory pressure control to cure hot-start or low-rail-pressure issues caused by a leaking PRV.
- ✓ Built to Cummins/Bosch spec for sealing and durability.
Quick Specs
| Type | Fuel rail pressure relief valve (common-rail) |
|---|---|
| OE Part # | 3947799 |
| Alternate IDs | BOSCH 1110010029 / F00R00632 (reference) |
| Qty Required | 1 per engine (sold individually) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2003–2007 | Ram 5.9L ISB (24V Common-Rail) | Ram 2500/3500 |
Industrial/Off-Highway: Also used on select ISB/QSB 5.9 common-rail engines—verify by ESN before ordering.
Often Paired With
- Fuel Rail Sealing Washers / Banjo Seals (as applicable to your rail)
- Fuel Filter (replace after any fuel-system service)
- Diagnostic Scan to clear codes and verify commanded vs. actual rail pressure after install
What’s In The Box
- (1) Genuine Cummins Fuel Rail Pressure Relief Valve (3947799)
- Seals/hardware sold separately if required by your rail configuration
Install Tips
- Depressurize the rail; wear eye protection. Torque to factory spec.
- After installation, prime system, check for leaks, and verify rail pressure.
- If symptoms persist (hard hot starts / rail pressure codes), test rail sensor and FCA as well.
FAQ
WILL THIS FIT MY 2003–2007 5.9L CUMMINS RAM?Yes—this OE PRV fits 2003–2007 5.9L ISB common-rail Ram 2500/3500 (verify by VIN/ESN).
WHAT ARE COMMON SYMPTOMS OF A FAILING PRV?Hot-start issues, low commanded vs. actual rail pressure, and rail pressure codes (e.g., P0087). A leaking PRV can bleed off pressure.
CAN I SHIM OR BLOCK THE RELIEF VALVE?We recommend the genuine OE PRV for safe pressure control. Blocking/shimming can risk injector and pump damage.
IS THIS A GENUINE CUMMINS/BOSCH COMPONENT?Yes—OE Cummins 3947799 built to Bosch specifications for proper pressure regulation.
DO I NEED NEW SEALING WASHERS?Some rails use replace-once sealing washers. Inspect and replace any damaged or flattened seals during installation.
