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The INP-780 & INP-781 Set at a Glance

The Set 4 INP-780 & INP-781 Fuel Injector is a direct-fit, multi-port fuel injection (MPFI) replacement engineered for the Mazda FP-DE 1.8L and FS-DE 2.0L platforms, covering 1999–2002 Protege and 626 models. You get a matched set of four: 2× INP-780 for cylinders 1 and 2, plus 2× INP-781 for cylinders 3 and 4.

Each injector carries high-impedance solenoid windings (12–16 Ω) and precision-ground pintle nozzles for consistent atomization and fuel-trim stability across cylinders. Projected service life: 80,000–120,000 miles over a 2026–2030 driving cycle.

• Engine fitment: FP-DE 1.8L (Protege) and FS-DE 2.0L (626), 1999–2002
• OEM cross-reference: 842-12285F8, 842-12285, 842-12122, 217-1717, FP3513250, GBR 842-12285
• Included: 2× INP-780 + 2× INP-781 (set of 4)
• Impedance: High-Z 12–16 Ω — works with stock ECU drivers

2026 Market Context and Compliance

As of May 2026, the global fuel injector aftermarket is valued at $80.39 billion with a 7.1% CAGR. Two forces drive that growth: stricter EPA Tier 3 emissions enforcement and the SAE GFISC's updated gasoline fuel-injection standards (SAE MA-07270).

This set holds OEM-matching spray-pattern and flow-rate tolerances aligned with 2026 aftermarket compliance expectations, and it supports the OBD-II diagnostic protocols (ISO 9141-2 / SAE J1979) used on every 1999–2002 Protege and 626 — so scan-tool data stays accurate after the swap.

How the Injectors Are Built

PPS/PA66 composite bodies

The bodies are molded from high-temperature glass-fiber-reinforced thermoplastic (PPS/PA66), aligned with 2026 SAE J2712 endurance criteria for under-hood thermal cycling from −40°C to +150°C. Internal seals are fluorocarbon (FKM/Viton) compounds rated for continuous E15 exposure at 150°C peak temperatures.

Legacy metal-bodied injectors are prone to internal corrosion from ethanol blends (E10–E15), and older OEM seals used natural rubber that ethanol attacks oxidatively. With the EPA's 2026 Renewable Fuel Standard pushing E15 across the U.S. retail fuel supply, the PPS composite's resistance to fuel-phase separation degradation is a practical advantage, not a marketing line.

4-hole disc nozzle, 15°–20° cone

Each unit carries a 4-hole disc-type nozzle plate with laser-drilled orifices optimized for the FP/FS combustion chamber geometry. The narrow atomization cone cuts intake-valve wetting and carbon buildup — a known failure vector on 1999–2002 Protege engines that commonly triggers P0300 and P0171 diagnostic trouble codes.

Solenoid and electrical ratings

Coil assemblies are epoxy-sealed and rated for continuous duty at 14.4V nominal, with surge tolerance up to 18V for alternator load-dump scenarios. Connectors are USCAR / EV1-style with a Mazda-specific key, and the operating window runs 8–18 VDC.

Specification Comparison: INP-780 vs INP-781

Note: INP-780 and INP-781 differ primarily in connector keying and cylinder-position assignment. Both share identical flow-rate and impedance profiles, so check connector fitment before installation.

Fitment, ECU Drivers, and Emissions

Two engines, one fuel rail architecture

The set is fully cross-compatible with the 1999–2002 Mazda Protege (FP-DE 1.8L) and the 1999–2002 Mazda 626 (FS-DE 2.0L) — both engines share the same fuel rail architecture, injector connector keying, and ECU injector-driver circuitry. The FS-DE 2.0L gains the most from the 4-hole nozzle, since its larger displacement places higher demand on atomization quality at mid-range RPM.

Saturated-driver injectors only

These are high-impedance (saturated-driver) injectors built for the stock Mazda FP/FS ECU. The 12–16 Ω range keeps the ECU's injector MOSFETs within safe thermal limits and prevents driver-circuit failure that can cascade into a no-start. Do not run them with aftermarket peak-and-hold (low-Z) driver modules unless you add an external resistor pack.

On emissions: as a direct replacement that maintains OEM-equivalent flow rates and spray patterns, the set is not an emissions defeat device under EPA 40 CFR Part 86 or CARB anti-tampering statutes. Installation on 1999–2002 model-year vehicles falls within the EPA's "reasonable basis" documentation framework for aftermarket parts that preserve the original emissions calibration.

Failure Symptoms and DTC Mapping

Injectors on aging FP/FS engines degrade in a predictable order. Watch for four progressive signs, and replace before the misfires start migrating between cylinders:

1. Cold-start hesitation — pintle stiction causes a lean stumble for the first 10–30 seconds.
2. Fuel trim divergence — STFT beyond ±10% on individual cylinders, visible via Mode $06 data.
3. Increased HC emissions at idle — unburned fuel from poor atomization.
4. Intermittent P0301–P0304 — cylinder-specific misfires that move around as multiple injectors degrade.

Codes this set addresses

• P0170–P0171: Fuel Trim Malfunction / System Too Lean (Bank 1)
• P0300–P0304: Random Misfire / Cylinder-Specific Misfire (Cyl 1–4)
• P0172: System Too Rich — possible with a stuck-open injector, though rare on this platform

Every code above reads through generic OBD-II (ISO 9141-2) and OEM-enhanced Mazda scan tools, including 2026-compliant ELM327 and J2534 pass-through interfaces.

Before you pull the fuel rail

Lean codes have copycats. If you're tracing vacuum faults first, the K5T49090 vacuum solenoid valve fits the 626, Millenia, MPV Cargo, MX-6, and Protege — a cheap part to rule out before you commit to injector work.

At 80,000+ miles on original injectors, proactive replacement is cost-justified: 2026 shop labor runs $120–$165/hr, so a second visit costs more than the parts. While the car is on the lift, these front ceramic brake pads for the 2001–2003 Protege and 2002–2003 Protege5 pair naturally with the same service window.

FAQ: Fitment and 2026 Diagnostics