Diesel heater soot build-up and the high-power clean burn

Why does my diesel heater soot up?

Owners traced soot to four things.

• Long running on a low setting. One owner had two identical heaters in identical garages: the one run mostly on minimum sooted up, the other did not. Owners One owner filled a new heater’s chamber with loose carbon in a few weeks of 15 to 20 minute runs at low heat. Owners
• A rich mixture. One owner of a 2 kW unit found it set up with large-heater pump and fan values; changing them in the settings menu stopped the soot. Owners One owner cleaned a heater three times before getting the pump settings right. Owners Two owners cured rapid sooting by fitting a different fuel pump. Owners One owner with the tank 2 to 3 ft above the heater ended daily sooting by moving the tank level with the heater. Owners
• Altitude. One owner’s heater was full of soot after 14 hours on low above 6,000 ft. Owners The Vevor CY manual’s plateau mode exists for this: it changes the air to fuel ratio for thin air. Manual See altitude tuning.
• A restricted intake or exhaust. One owner had routed the exhaust through a coil; with the coil removed the sooting stopped. Owners The Dieselheat guide sends you to the air inlet and exhaust for partial blockage when a heater smokes all the time. Manual

Cutting the power can add to it. Gasmate’s manual says not to cut power during start-up or shut-down: it causes smoke at the next start, and repeated cuts cause carbon build-up. Manual

What are the signs of soot build-up?

• The heater gradually loses heat and gets harder to start. Owners
• White smoke appears after a period of running. The Vevor CY manual reads that as a clogged atomising screen at the glow plug. Manual
• Black smoke appears after a period of use or in the second year. The Vevor CY manual reads that as carbon in the combustion chamber. Manual
• The heater ends on a flame-out or failed-start code. Which number that is depends on the controller: see the table above.

How long should the high-power clean burn be?

The documents do not agree, so here is each one.

All three rows are from manuals. Manual They were written for different heaters. Use the one for your own heater if you have it.

Two documents also cover a heater that is already smoking:

• Dieselheat’s portable guide: for excessive smoke after long low-power running, run 2 hours on full power. Manual
• Dieselheat’s fault-finding guide: if it still smokes after 15 min on full power, with the air inlet and exhaust checked, it needs a service. Manual

Does the clean burn actually work?

Seven owners in five threads describe running on high to keep soot down, six as a habit and one as a one-off cure, and none of them reports soot trouble since. Owners Their routines differ:

• 15 to 20 minutes on high before packing up.
• Starting on full power, and 15 minutes on full before switching off: second winter, never opened.
• A couple of minutes on high before shutdown, together with a pump setting lowered for altitude.
• A blast on high before switching off.
• A burn at maximum at the end of each season: found clean when opened after two seasons.
• Occasional 5-minute full-power runs in six months of full-time use. This owner is unsure the runs matter.
• A couple of hours on high once, after which a heater that had not been firing first try started first time.

The limits of this evidence: nobody measured anything. These are habits and a few before and after cases, and three of these owners changed something else as well (a pump setting or the fuel). A high-power run also does not fix a cause that is still there. The owners with wrong pump values, an oversupplying pump or a restricted exhaust had to fix those.

What should I check, and in what order?

1. Intake and exhaust. With the heater off and cold, check both pipes for partial blockage. Dieselheat’s guide makes this the first check for constant smoke. Manual
2. Run it on high. Use the interval from your own manual, or one of those in the table. If it still smokes after the time your document gives, go on.
3. Altitude. If you are well above sea level, switch on the plateau or Alpine mode if the panel has one: see altitude tuning.
4. Pump and fan values. On a panel with a PIN menu, compare the values with what the heater came with. Write the originals down before changing anything: see the hidden settings menu.
5. Tank height and pump. If the tank sits well above the heater, try it level with the heater, as one owner did. Owners If sooting returns within days of a clean, suspect the fuel pump, as two owners found. Owners
6. Glow plug screen. A clogged screen is the next stop: see cleaning the glow plug and its screen.

When does the burn chamber need cleaning?

When the cheaper checks make no difference and the heater still only smokes or will not light. Two owners got their heaters running by emptying carbon out of the burn chamber: for one a new glow plug and screen had changed nothing, for the other a new pump and fuel lines. Owners A third burnt carbon out of the chamber and exhaust but changed other things at the same time and is not sure which step worked. A fourth found the chamber burnt out inside and replaced it. Owners The Vevor CY manual’s answer to carbon in the chamber is to remove the shell, the main board, the fan assembly and the combustion chamber, and fit a new chamber. Manual

Opening the chamber means new gaskets and careful reassembly of a part that carries exhaust gas.

If you are not sure, ask a technician. Opening the combustion chamber goes beyond routine owner maintenance. A mistake here can cause a fuel or exhaust leak. Stop if anything is unclear.