Code Details
| Display code | SPN 94 FMI 1 |
|---|---|
| SPN | 94 |
| FMI | 1 |
| OEM code | None listed |
| Manufacturer | Mack |
| System | Engine �?fuel system |
| Component | Fuel lift pump / fuel filter / supply circuit |
| Source address | Unknown or not applicable |
| Severity | high |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-12 |
Plain-English Meaning
The Mack MP8 and the Volvo D13 share the same basic fuel system architecture �?a gear-driven lift pump supplies low-pressure fuel to the high-pressure injection pump. SPN 94 FMI 1 on a Mack Anthem, Pinnacle, or Granite equipped with the MP8 indicates that the lift pump supply pressure is below normal. A clogged fuel filter is the leading cause; a failing lift pump or air ingestion are the next most common.
SPN 94 FMI 1 is Fuel Delivery Pressure below normal range. On Mack MP8 with EMS3 engine management, VCADS Pro (also accessed via PTT �?Premium Tech Tool) displays fuel delivery pressure in live data. A systematic check comparing delivery pressure at idle versus under load helps distinguish between a filter restriction (pressure drops significantly under load) and a pump failing at baseline (pressure is low at all conditions).
Common Symptoms
- Power loss under heavy load conditions
- Hard starting, especially after the truck has been parked
- Engine stumble or surging
- SPN 157 may appear alongside
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Clogged primary or secondary fuel filter
- Lift pump deterioration or mechanical failure
- Air ingestion from a supply-side fitting leak or low tank level
- Restricted fuel supply line from the tank
- Fuel delivery pressure sensor fault
First Checks
- Replace the fuel filter �?the most common resolution for SPN 94 FMI 1 on the Mack MP8
- Use VCADS Pro to monitor fuel delivery pressure with fresh filters under idle and load conditions
- Check for air in the system by inspecting the return line (if transparent) and supply fittings
- Inspect fuel supply line routing for restriction, damage, or freeze-related collapse
- If delivery pressure remains low with new filters and no air leak, test lift pump output pressure directly
Can I Keep Driving?
The Mack MP8 may reduce power to protect the fuel system. Address promptly to avoid HP pump and injector damage.
Related Codes
Related Lookup Pages
Sources
- Mack Trucks Service Support Public Resources Mack Trucks Inc. · oem · accessed 2026-06-11 · confidence medium
Source: Mack Trucks Inc., Mack Trucks Service Support Public Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - Volvo Trucks / Mack Trucks Technical Support Volvo Trucks North America / Mack Trucks Inc. · oem · accessed 2026-06-10 · confidence medium
Source: Volvo Trucks North America / Mack Trucks Inc., Volvo Trucks / Mack Trucks Technical Support. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
Is the Mack MP8 fuel filter the same part as the Volvo D13 filter?
The Mack MP8 and Volvo D13 share the same engine platform, and in many configurations the fuel filter is the same part. Confirm by using VCADS Pro parts look-up or the Mack/Volvo parts portal with the specific engine serial number to confirm the correct filter part number for the application.
Will a Mack Anthem MP8 set SPN 94 FMI 1 if the fuel tank is nearly empty?
Yes. Running the fuel tank very low can allow air to enter the supply line, particularly on a truck that sits at an angle or after aggressive cornering. If SPN 94 FMI 1 appears alongside a low fuel level, refueling and priming the system is the first step. If the code persists after refueling and the engine returning to normal operation, inspect the fuel cap and fill for air entry points.
Can I use PTT or only VCADS Pro to diagnose fuel delivery pressure on the Mack MP8?
PTT (Premium Tech Tool) is the Mack-branded version of the same diagnostic software platform used as VCADS Pro for Volvo. Both provide access to Mack MP8 live data including fuel delivery pressure. The diagnostic capability is equivalent �?the naming differs by brand but the tool connects to the same EMS3 engine management system.