Retiring the Carburetor: Fuel Injection for a 1984 Nissan 720
The truck in question is my 1984 Nissan 720 — a four-wheel-drive hardtop that's been around the block a few dozen thousand miles. It runs, but it runs like it does: great once warm and at sea level, grumpy when cold, and noticeably worse on every hill. The carburetor has done its job for forty years. Its job is about to end.
Why fuel injection
- Cold starts. No choke dance, no flooded morning cranks — just a consistent air/fuel mixture from the first revolution.
- Altitude consistency. Injection meters fuel by mass/flow and compensates where a carb just leans out as you climb.
- Throttle response & drivability. Especially with load on — 4×4 trucks live under load.
What the conversion involves
At a high level, any carb-to-FI conversion on an engine this old is the same four pieces of work:
| Air side | Throttle body replacing the carb (and plenum/intake cleanup) |
| Fuel side | Injectors + fuel rail, regulator, and a pump/rate that matches the engine's flow needs |
| Brain | An ECU — either an era-correct unit from a Nissan FI engine or a standalone controller — with maps for this engine |
| Sensing & wiring | Crank/cam position signals, TPS, and a harness that survives a truck's vibration environment |
Status
- [ ] Decide: OEM-era FI swap vs. standalone ECU + injectors
- [ ] Source throttle body, injectors, and fuel system components
- [ ] Wire the sensing side; first idle on injection
This is a slow project — parts for a 40-year-old truck are sourced one auction at a time. Updates as things land in the driveway.