Symptoms
Poor idle, flat throttle response, fuel starvation, or orange flakes in the fuel filters.
The fix, step by step
- Expedition Imports' advice is to treat the whole fuel system, not just the carb: filters (there's more than one), both tanks, the selector valve, the pump and the lines.
- Rebuild the carb with a proper kit and actually set the float level.
- Check the idle mixture screws, which are often damaged from being screwed in too far.
- Most 404s come with 140 main jets, and owners above 5,000 ft may want 130–135s.
- If the tank lining is flaking, flush the tank or have it sealed.
- Do the tune-up (valves, ignition) before you tune the carb.
Tools & part numbers
- Float-level gauge
- carb synchronizing tool
- screwdrivers
- spare gasket kit. An ethanol-compliant pump diaphragm is worth fitting on today's fuel.
Where to buy the parts
Carb rebuild kit, Zenith 32 NDIXExpedition Imports ↗Amazon ↗
Zenith 32 gasket kitExpedition Imports ↗Amazon ↗
Fuel pump diaphragm, ethanol compliantExpedition Imports ↗Amazon ↗
Inline fuel filter elementExpedition Imports ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz Unimog 404 parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.