First start: setting up a new ECU and starting the engine
The settings to get right before the engine turns over, how to confirm the ECU sees the crank correctly, and what to check in the first minutes of running.
Before you power the ECU
Most first-start problems are wiring, not tuning. An hour of checks with a multimeter saves days of chasing a fuel table that was never the problem.
- Check every ground goes to the engine block or the battery negative, and that sensor grounds use the ECU's sensor ground, not the chassis.
- Confirm the fuel pump runs and the regulator holds the pressure your injector data was measured at, usually 3 bar (43.5 psi).
- Disconnect the injectors, or pull the fuel pump fuse, for the first cranking test. You want to see RPM and spark before any fuel goes in.
- Make sure you know which output fires which cylinder. A swapped coil or injector looks like a bad tune.
Engine and injector settings
The ECU can only calculate fuel and spark from what you tell it about the engine. Set these before any table:
| Setting | What it controls | Where to find the number |
|---|---|---|
| Displacement and cylinders | The air mass the fuel calculation starts from | Engine specification |
| Injector flow | How long each pulse must be | Injector data sheet, at your fuel pressure |
| Injector dead time | Time the injector takes to open, added to every pulse | Injector data sheet, by battery voltage |
| Injection mode and squirts | Batch, semi-sequential or sequential, and pulses per cycle | Your wiring and whether you have a cam sensor |
| Ignition mode | Distributor, wasted spark or coil on plug | Your coils and wiring |
| Dwell | How long each coil charges | Coil data sheet |
On Speeduino and MegaSquirt, injector flow and displacement go through the Required Fuel calculator. rusEFI and epicEFI take them directly. The injector sizing guide explains each number.
Trigger setup and checking timing
The trigger is how the ECU knows where the crank is. Choose the trigger pattern that matches your wheel (36-1, 60-2, 4-1 and so on) and whether there is a cam sensor. Then crank the engine with the injectors disabled and watch RPM: it should read a steady cranking speed, usually 150 to 300 rpm, with no sync losses.
Next, line the ECU's idea of top dead centre up with the real one. Every firmware has an offset for this:
- Speeduino: Trigger Angle, in Trigger Settings.
- rusEFI and epicEFI: Trigger Angle Advance.
- MegaSquirt MS3: Tooth #1 Angle, among the ignition options.
- Fix the timing to a known number, such as 10° BTDC. Speeduino and rusEFI both have a fixed or locked timing option for this.
- Crank or idle the engine and point a timing light at the crank pulley mark.
- Change the offset until the light shows the number you fixed. Wasted-spark systems show the same mark on both strokes, so check you are on the compression stroke.
- Turn fixed timing off. The spark table now means what it says.
Skipping this step is the most common cause of an engine that runs badly no matter what you do to the tables. If the offset is out by 10°, every cell in the spark table is out by 10°.
Base tables
You don't need a finished tune to start an engine, but you need a plausible one: a VE table with sensible shape, AFR targets around stoichiometric at idle and richer under load, a conservative spark table, and cranking and warm-up fuel that suit the temperature.
- VE: a gentle rise with load and a peak near the torque peak. On a typical naturally aspirated engine idle cells land somewhere around 35–50 %.
- AFR targets: near 14.7 (lambda 1.0) at idle and cruise, 12.5–13.0 at full load, richer again on boost.
- Spark: 10–15° at idle, conservative under load. Too little advance runs hot; too much risks knock.
- Cranking fuel and priming: start from the firmware's defaults. The cold start guide covers them.
The first minutes of running
- Start logging before you turn the key, so the start itself is recorded.
- Once it fires, watch oil pressure first. No oil pressure means shut it off, whatever the tune is doing.
- Hold a fast idle with the throttle if needed and check AFR. Fix gross rich or lean conditions by scaling the idle VE cells.
- Recheck timing with the light now that the engine is running steadily.
- Watch coolant temperature and check for fuel, oil and coolant leaks.
- Let it reach operating temperature before tuning idle or VE. Cold-engine fuel belongs in warm-up enrichment.
Using efi2000 for a first start
Generate a base tune
Generate tables builds starting VE, AFR target and spark tables from the engine details in Vehicle properties: displacement, cylinders, injectors, aspiration and fuel. You preview each table before it is applied.
Check before you write
Spotter reviews the tune for mistakes that matter on a first start, such as an AFR target table that's lean at load or a spark table that's implausibly advanced, and explains each finding.
Record from the first crank
Turn on continuous logging in Logs → Log settings before the first crank. It is off for a new project; once on, it records whenever the ECU is connected, so the first start is in a log even if you forget to press record. Open it in the log viewer afterwards to see RPM, AFR and timing through the start.
Questions
- The engine cranks but the RPM reads zero. What's wrong?
- The ECU isn't seeing the trigger. Check the trigger pattern matches your wheel, the sensor type (VR or Hall) matches its input, and the sensor gap and polarity. A VR sensor wired backwards often gives an erratic or missing reading.
- Should I start with a tune from a similar engine?
- It can save time if the injectors, displacement and firmware match. Copy the tables, not the hardware settings: trigger, pins and injector data must match your build.
- Does efi2000 work for a first start?
- Yes. Load your firmware's INI, set up Vehicle properties, generate or import a tune, and connect over USB in desktop Chrome or Edge to write it.