Code Details
| Display code | SPN 94 FMI 1 |
|---|---|
| SPN | 94 |
| FMI | 1 |
| OEM code | None listed |
| Manufacturer | Detroit Diesel |
| System | Engine �?fuel system |
| Component | Fuel lift pump / fuel filter / supply lines |
| Source address | Unknown or not applicable |
| Severity | high |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-12 |
Plain-English Meaning
The DD13 fuel system relies on a gear-driven lift pump to supply low-pressure fuel to the high-pressure injection pump. When supply pressure drops below the ECM threshold, the high-pressure pump cannot build adequate rail pressure. The DD13 is used in Freightliner Cascadia and Western Star configurations where shorter wheelbase and lighter spec requirements are needed. Like the DD15, the most common cause of SPN 94 FMI 1 on the DD13 is a clogged primary fuel filter. On Freightliner Cascadia and Western Star trucks with the Detroit DD13, SPN 94 FMI 1 is almost always resolved by replacing the primary fuel filter. DiagnosticLink records the fuel delivery pressure before and after filter replacement, providing documentation for the repair. If pressure remains below specification after a confirmed filter change, the DD13 lift pump should be tested by measuring output pressure directly at the pump outlet with a calibrated gauge.
SPN 94 FMI 1 is Fuel Delivery Pressure below normal range. On Detroit DD13 with MCM2.0, DiagnosticLink monitors fuel delivery pressure as a live parameter. Comparing delivery pressure at idle versus under load distinguishes a filter restriction from a pump performance issue.
Common Symptoms
- Reduced power under load
- Hard start or extended cranking
- SPN 157 (fuel rail pressure) may appear simultaneously
- Engine stumbles or hesitates on acceleration when fuel supply drops momentarily
- SPN 157 (fuel rail pressure low) may appear simultaneously
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Clogged primary fuel filter
- Lift pump worn or failing
- Air ingestion from supply side
- Restricted fuel supply line
- Water-in-fuel from contaminated diesel supply causing rapid filter plugging
- Fuel tank pickup screen fouled with sediment
First Checks
- Replace the fuel filter �?the most common resolution for DD13 SPN 94 FMI 1
- Connect DiagnosticLink and monitor fuel delivery pressure with fresh filters
- Inspect supply lines for restriction or kinks
- If pressure remains low after filter change, test lift pump output
- Drain the fuel filter water separator bowl and note water or sediment
- After filter replacement, monitor DiagnosticLink fuel delivery pressure under various load conditions
Can I Keep Driving?
Reduced power and potential derate. Address promptly to protect fuel system components.
Related Codes
Related Lookup Pages
Sources
- Detroit Diesel Service and Diagnostic Resources — Public Reference Detroit Diesel (Daimler Truck North America) · oem · accessed 2026-06-11 · confidence medium
Source: Detroit Diesel (Daimler Truck North America), Detroit Diesel Service and Diagnostic Resources — Public Reference. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - DiagnosticLink Detroit Diesel Corporation · oem · accessed 2026-05-05 · confidence medium
Source: Detroit Diesel Corporation, DiagnosticLink. 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 Detroit DD13 fuel filter the same part as the DD15?
The DD13 and DD15 are different displacement engines with different fuel system flow requirements, so fuel filter part numbers typically differ. DiagnosticLink or the DTNA parts system confirms the correct filter specification for the DD13 serial number.
How does the DD13 fuel delivery pressure spec compare to the DD15?
Both engines require adequate lift pump delivery pressure, but the specific thresholds may differ based on engine rating and calibration. DiagnosticLink displays the actual delivery pressure for comparison to the calibration specification for each engine.
Can I drive a short-wheelbase Freightliner Cascadia with a DD13 to a dealer with SPN 94 FMI 1 active?
Short-distance, low-load driving to a service facility is generally possible if the engine is not in a severe derate. Continued high-load operation with low fuel delivery pressure risks HP pump and injector damage. Reduce load and speed if necessary to limp to service.