Product Description
CUMMINS 3866798 OEM INJECTOR FUEL SUPPLY LINE SET – RAM 5.9L 12-VALVE (1994–1998) | BOSCH P7100
The genuine CUMMINS 3866798 OEM Injector Fuel Supply Line Set restores factory-correct fuel delivery and precise injection timing on all 1994–1998 5.9L Cummins 12-valve engines equipped with the legendary Bosch P7100 (P-pump). These lines are engineered to match the exact diameter, wall thickness, bend geometry, and vibration-resistant flare design specified by Cummins for the 6BT platform.
Each hard line maintains the precise length and internal volume required for consistent cylinder-to-cylinder fueling—critical for performance, smooth running, emissions stability, and injector longevity. If your original lines are rusted, cracked, leaking at the flare, or distorted from injector service, this OEM set is the only correct replacement.
Pair these lines with genuine Cummins sealing washers and related fuel system components to ensure long-term, leak-free performance. For boosted reliability and alignment with factory service procedures, match them with the CUMMINS 3939258 inlet banjo and CUMMINS 3943106 connector tube seal kit.
Key Features
- Genuine Cummins OEM hard line set – not aftermarket copies.
- Exact P7100-specific lengths and bends to maintain correct timing characteristics.
- High-strength steel construction for vibration resistance and long service life.
- Correct flare geometry ensures leak-free sealing at the pump and injectors.
- Direct-fit for all 1994–1998 12-valve trucks – Ram 2500 & 3500 with 5.9L Cummins.
Fitment Details
- Engine: 5.9L Cummins 6BT / 12-Valve
- Injection Pump: Bosch P7100
- Model Years: 1994, 1995, 1996, 1997, 1998
- Vehicles: Dodge Ram 2500 / 3500 (Federal & California where equipped)
Note: Injector lines are engineered by cylinder number—do not interchange positions. Always verify injector seating depth and connector tube condition before installation.
Cross-Reference & Compatible Cummins Parts
- CUMMINS 3943106 OEM INJECTOR CONNECTOR TUBE SEAL KIT – 5.9L
- CUMMINS 3939258 P7100 INJECTION PUMP INLET BANJO BOLT
- CUMMINS 3939259 OEM INJECTOR CONNECTOR TUBE – 5.9L 12V
- VIEW MORE GENUINE CUMMINS PARTS
Common Cummins cross-reference numbers: 3866798, 3935817, 3935818, 3935819, 3935820, 3935821, 3935822 (individual line references vary by cylinder).
Installation Notes
- Always clean injector bores and tube seats before reassembly.
- Use new sealing washers and connector tube O-rings.
- Start all fittings by hand to avoid cross-threading.
- Tighten flare nuts evenly to prevent leaks and distortion.
- Prime system and check for leaks while cranking, then at idle after warm-up.
Specifications for cummins 3866798
| Attribute | Value |
|---|---|
| Brand | Cummins (Genuine OEM) |
| Part Number | 3866798 |
| Alternate / Related Cummins Numbers | 3935817–3935822 (cylinder-specific line references), 3939259 (connector tube), 3943106 (seal kit) |
| Function | Injector fuel supply hard line set for P7100-equipped 5.9L 12-valve engines |
| Engine Compatibility | 5.9L Cummins 6BT / 12-Valve |
| Vehicle Fitment | 1994–1998 Dodge Ram 2500 / 3500 |
| UPC / Barcode | 750361386798 |
| GTIN | 00750361386798 |
| Shipping Weight | Approx. 2.5–3 lbs (complete set) |
| Shipping Method | Standard ground shipping; protective packaging included |
| E-Codes / Emissions | Used on 12-valve mechanical injection engines; not emissions-controlled electronically |
| Prop 65 Warning | WARNING: This product can expose you to chemicals including diesel fuel and metal residues known to cause cancer. For more information, visit www.P65Warnings.ca.gov. |
| Country of Origin | As labeled by Cummins (varies by production batch) |
Frequently Asked Questions
WILL THIS FIT ALL 1994–1998 12-VALVE CUMMINS TRUCKS?
Yes. This set fits all 1994–1998 Ram 2500/3500 trucks equipped with the Bosch P7100 pump. Always verify your pump tag and injector configuration during service.
DO THESE LINES HAVE CYLINDER-SPECIFIC ROUTING?
Yes. Each line is engineered for a specific cylinder. Mixing them will affect fuel timing and may cause misfire or rough operation.
SHOULD I REPLACE CONNECTOR TUBES WHEN INSTALLING NEW LINES?
It is strongly recommended. The connector tube sealing surface wears over time. Use CUMMINS 3939259 and the CUMMINS 3943106 seal kit for a complete service.
ARE THESE LINES AFTERMARKET OR GENUINE CUMMINS?
These are genuine Cummins OEM fuel supply lines. Avoid aftermarket copies, as improper wall thickness and bend geometry can cause timing issues.
WHAT CAUSES INJECTOR LINES TO FAIL?
Common causes include vibration fatigue, improper torque, injector swaps bending the lines, or corrosion. Replace any line showing cracks, fuel seepage, or distortion.
