Start a wood gas vehicle outdoors by lighting a pilot at the flare first, then lighting the gasifier with the start-up blower pulling air in through the lighting port, and keep the blower running for 10-15 minutes until the gas burns at the flare with a steady flame that stays lit when the igniter is withdrawn. Only then start the engine on petrol, switch over to gas, and idle for 2-3 minutes, for a total of 20-30 minutes; the first minutes of gas are cool, rich and almost entirely carbon monoxide, and no one should have their face near the unit.
Part of Operating Procedures
The start-up sequence takes a cold gasifier to usable gas and the engine from petrol to gas, with the gas burnt at a flare until it is clean.
Why The First Minutes Are The Dangerous Ones
Before the bed is hot, there is no hot throat to crack tar and no deep glowing bed to reduce carbon dioxide, so the gas is cool, tarry and rich in carbon monoxide relative to everything else. It is also weak and may not burn on its own. This is when the operator is bent over the lighting port with a torch, which is the worst place to be. The sequence below is built so that nobody needs to lean over the unit and so that any gas that appears goes to a flare and is burnt.
The carrier’s own start-up has you light a torch at the lighting port, run the fan, test the gas by holding a flame to the outlet pipe after 10-15 minutes, start the engine on petrol, switch to gas, and warm up for 2-3 minutes. The version here changes two things: the flare is lit before the gasifier, and the gas test is done at a deliberate flare, never as a flame held to a pipe that may be leaking.
What You Need
- A flare ending outdoors above head height, on a short welded pipe from the blower outlet, with a pilot torch or taper at its end. A flame at a vent that burns gas on purpose is a flare. It is not a leak detector.
- A blower or fan on the gas outlet side, pulling air in through the lighting port and nozzles.
- A long-handled torch or taper for the lighting port.
- A dry fuel load of 3-5 cm chunks at 20% moisture or below on a wet basis (25% dry basis).
- Closed and tested valves: ash door shut, drains closed, and separate valves to the engine and to the flare, with the engine valve closed at the start.
Method: The Timeline
| Minute | Action | Check |
|---|---|---|
| 0 | Park outdoors, wind at your back, away from walls and buildings. Load fuel and close the lid. Check ash door, drains, joints. | Lid and ash door tight |
| 1 | Light the pilot at the flare. Start the blower. | Air is drawn in at the lighting port, not blown out |
| 2-3 | Hold the long torch at the lighting port, standing to the side and upwind; do not lean in. Withdraw it when the fuel is burning and close the port. | Fire established; no flame or smoke from the lid |
| 4-10 | Leave it. The flare receives smoke and weak gas. Do not approach the unit. | Smoky, sooty flare at first |
| 10-15 | The flame steadies to a pale blue to yellow colour and keeps burning without the pilot. Hold it steady for at least a minute. | If sooty or sputtering, keep the blower running; do not connect the engine |
| 15-18 | Start the engine on petrol and warm it. | Engine running smoothly on petrol |
| 18-20 | Open the gas valve gradually, close the petrol, and adjust the mixer. Close the flare valve when the engine runs on gas and the blower is off. | Smooth running; flare out |
| 20-23 | Idle for 2-3 minutes on gas. | Steady idle |
| 23-30 | Drive away gently and keep the revs up. |
The table reaches the drive-away at about 23 minutes. The carrier states 20-30 minutes in all, and the extra is slack for fuel loading and for a bed that is slow to establish in cold or damp conditions.
Reading The Flare
- Steady pale blue to yellow, stays lit: combustible gas in quantity. Proceed.
- Smoky, sooty, orange or yellow-white, drips tar: the throat is cold or the fuel is wet. Keep the blower on. If it is still sooty at 25 minutes, shut down and investigate rather than connecting the engine.
- No flame at all after 15 minutes: no gas is being made. Check for bridging in the hopper, blocked nozzles, a leak at the lid or ash door, and wet fuel. Do not open the unit hot.
Common Mistakes
- Cranking the engine to pull gas through. The carrier mentions it, but cranking draws unburned gas out through the exhaust and into the air around you. Use the blower and a flare.
- Switching to gas at the first flame. The gas is not yet clean.
- Leaning in to see the fire. The face is over the worst gas.
- Stopping the blower before the engine pulls steadily. The gas stalls and the flare goes out.
Safety
Start-up gas is almost entirely carbon monoxide and the vessel can flash back
Before the fire is established the gas is cool, rich and almost all carbon monoxide, odourless and colourless; the tar smell tells you nothing about it. Carbon monoxide binds to haemoglobin about 200 times more strongly than oxygen, and the early symptoms (headache, nausea, clumsiness, confusion) remove the judgement needed to leave. Never light, warm up or vent a gasifier in a garage, shed, lean-to or enclosed yard, even briefly, and never sleep in or near the vehicle with it lit. A hot bed full of gas can flash back or explode if the lid is opened or on restart: do not open a hot unit. Keep the flare pointing away from the cab and from fuel. See CO Risk and Carbon Monoxide Risks.
What’s Next
- Learn next: Driving Technique — running on gas once it is established
- Combine with: Emergency Procedures — what to do if the start-up goes wrong