CUMMINS
CUMMINS 3900808 OEM 9MM FUEL INJECTOR SEALING WASHER – 5.9L CUMMINS (1989–1991)
(No reviews yet)
Write a Review
- SKU:
- CUM3900808
- MPN:
- 3900808
- Shipping:
- Calculated at Checkout
Description
Genuine Cummins
Cummins 3900808 — 9mm Fuel Injector Sealing Washer (Copper)
MPN: 3900808 | Also Known As: injector washer, injector seal, nozzle seal | Cross-Refs: Bosch 2430105026
Why This Part
- ✓ OE copper washer for proper injector-to-head sealing.
- ✓ Correct 9mm size for early 1st-gen 5.9L Cummins.
- ✓ Prevents combustion leaks and maintains spray pattern.
- ✓ Sold individually — order 6 per engine.
OE Fit 9mm Tip 6 Req.
Quick Specs
| Type | Fuel injector sealing washer (copper) |
|---|---|
| OE Part # | 3900808 |
| Injector Tip Size | 9mm (early 1st-gen) |
| Qty Required | 6 per engine (sold individually) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 1989–1991 | 5.9L 12-Valve (VE pump) with 9mm injectors | Dodge 250/350 (1st Gen) |
Compatibility Notes: This washer is for 9mm injector tips. Later 1st-gen trucks with 7mm injectors use a different washer. Always confirm tip size or ESN before ordering.
Often Paired With
- Injector install kit / return line seals (year-appropriate)
- Injector seat cleaning tools to prep the bore
What’s In The Box
- (1) Genuine Cummins 9mm Injector Copper Washer (3900808)
- Order 6 for a full engine set (sold individually).
Install Tips
- Clean the injector seat; do not reuse old copper washers.
- Verify injector tip size is 9mm before installation.
- Torque injector hold-downs to spec and recheck after heat cycle.
FAQ
WILL THIS FIT MY 1989–1991 5.9L CUMMINS?Yes—this 9mm copper washer fits early 1st-gen 5.9L applications with 9mm injectors. Confirm tip size or ESN if unsure.
HOW MANY WASHERS DO I NEED?Order 6 washers per engine (one per injector).
IS THIS FOR 9MM OR 7MM INJECTORS?This is the 9mm washer. Later 1st-gen trucks use 7mm injectors and require a different washer.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins 3900808 copper injector sealing washer.
CAN I REUSE MY OLD WASHERS?Reusing can cause combustion leaks and poor spray pattern. Always install new washers on reassembly.
Additional Information
Vehicle Year: |
1989,1990,1991 |
Vehicle Make: |
DODGE |
ENGINE: |
5.9L |
Part Type: |
9mm Injector Sealing Washer |
Related Products
Related Products
CUMMINS 3918188 OEM 8MM FUEL SYSTEM SEALING WASHER – RAM 5.9L (1989–1998)
CUMMINS
$7.91
Genuine Cummins
Cummins 3918188 — 8mm Fuel System Sealing Washer
MPN: 3918188 | Also Known As: banjo bolt sealing washer, bonded sealing washer | Use: Fuel
CUMMINS 4942278 OEM FUEL INJECTOR RETURN LINE BANJO SEAL (WASHER) – RAM 5.9L 12-VALVE (1994–1998)
CUMMINS
$6.94
Genuine Cummins
Cummins 4942278 — Fuel Injector Return Line Banjo Seal / Washer
MPN: 4942278 | Also Known As: banjo connector seal, return line sealing washer | Use:
CUMMINS 3905307 OEM FUEL INJECTOR RETURN LINE BANJO BOLT – 5.9L 12-VALVE (1989–1998)
CUMMINS
$10.11
Genuine Cummins
Cummins 3905307 — Fuel Injector Return Line Banjo Bolt
MPN: 3905307 | Also Known As: banjo connector screw, injector return banjo bolt | Qty Per Engi
CUMMINS 3937111 OEM FRONT CRANKSHAFT SEAL SERVICE KIT – 5.9L CUMMINS (1989–2007)
CUMMINS
$69.53
Cummins 3937111 — Genuine Front Crankshaft Seal Service Kit for 5.9L Cummins
MPN: 3937111 | Also Known As: front main seal, crank seal, front crankshaft seal kit | ...
CUMMINS 4983584 OEM MECHANICAL FUEL TRANSFER (LIFT) PUMP – 5.9L CUMMINS (1989–1993)
CUMMINS
$221.02
Cummins 4983584 — Genuine Mechanical Fuel Transfer (Lift) Pump
MPN: 4983584 | Also Known As: mechanical lift pump, fuel supply pump | Common Cross-Refs (ID): 3970880,...