This is the online owner’s manual for the VVKB Zeus-F3 diesel fuel tank heater — a heated fuel pickup that installs on your tank’s existing pickup tube. In cold weather it warms only the diesel being drawn up the pickup, so your engine keeps getting clean, flowing fuel. Below: how it works, how to install it without drilling, how to wire it, and the safety rules that matter.
Why cold diesel stops your engine
As diesel cools, paraffin wax begins to crystallize. Around the cloud point (about 0 °C / 32 °F) the fuel turns hazy as wax forms; by the pour point (roughly −10 to −20 °C, depending on the blend) it will barely flow. Dissolved water freezes and blocks the filter media. The result is an engine that cranks but will not start, or that starts and then stalls as the fuel supply is starved. The wax clogs first where fuel is drawn and filtered — the pickup and the fuel filter.
What the Zeus-F3 does
The Zeus-F3 is a fuel pickup heater, not a cab heater. It does not burn fuel and it does not heat the whole tank. It installs on the pickup tube inside your tank and warms the diesel in the moments before it is drawn up the line, right where wax would otherwise clog the pickup. A built-in slot filter also screens out coarse debris.
The element is a self-regulating PTC: as it warms, its own resistance climbs and throttles it back, so it cannot overheat your fuel and there is no thermostat to set. Unlike inline or filter heaters, an in-tank pickup heater can work before the engine starts.
Specifications
| Voltage | 12 V (10.8–15 V) |
| Power | up to 150 W · 15 A fuse |
| Startup current | ≤ 10 A |
| Heating element | Self-regulating PTC (no thermostat) |
| Pickup tube | Ø 10 mm, up to 800 mm long |
| Min. tank opening | Ø 39 mm |
| Ambient range | −40 to +40 °C (−40 to +104 °F) |
| Protection | IP68 (in-tank) / IP67 (outside tank) |
| Duty | Continuous |
| Warranty | 12 months |
Installation — no drilling
The wires exit through the channel formed by the two grooved rubber gaskets that replace your stock flange gasket — you do not drill the tank or the flange.
- Disconnect the battery. Remove the tank’s pickup / sender unit.
- Slide the insulation sleeve onto the pickup tube, then push the heater onto the tube all the way to the stop. If you use a 1 mm gasket, shorten the pickup tube by 4 mm to keep the correct immersion depth.
- Tighten the two set screws until their slots line up with the ring groove, then fit the lock ring into the groove so the screws cannot back out.
- Route the wires through the groove channel between the two gaskets, and seal that channel fuel- and vapor-tight — diesel can wick up the wire strands.
- Leave about 150 mm (6 in) of wire from the gasket to the plug. Wrap excess wire around the pickup tube (over the sleeve) and secure with ties. Never secure the wire in a way that could pull it out of the heater.
- Refit the pickup into the tank.
Wiring
The kit includes a relay, 15 A fuse, button switch and LED.
- Battery (+) → 15 A fuse → relay → heater. Ground the heater’s negative lead to the vehicle body.
- Mount the push switch and LED on the dash within the driver’s reach. Switch cutout Ø 20.2 mm (with a 2.2 mm locating slot); LED bracket hole Ø 6.5 mm.
- Mount the relay and fuse under the dash panel; run the harness to the cab along the existing loom.
Using the heater
Press the dash button 3–5 minutes before you crank, in freezing weather. The LED on means it is heating. Switch it off once the engine is running and fuel is flowing. Only use it in below-freezing weather, when fuel pickup is difficult — it is a manual heater that you turn on and off.
Safety
- Diesel only. Never switch on with gasoline- or kerosene-blended fuel.
- Never switch on with less than 20 mm of fuel in the tank. There is no dry-burn protection — you must confirm fuel is present.
- Do not switch on above freezing (0 °C / 32 °F).
- Install or remove the pickup only with the heater switched off.
- Diesel vapor is explosive — no open flame where fuel is handled; use explosion-proof lighting.
- Clean the slot filter only with a blunt wooden stick, never a sharp metal tool.
Frequently asked questions
The filter is where diesel gels, so why heat the tank?
The heater sits on your pickup tube inlet, so it warms fuel in the seconds before it is drawn up the line — right where wax would clog the pickup and filter. It also works before the engine starts, when inline and filter heaters cannot.
Why not just use an anti-gel additive?
Additives work, but you buy and pour a bottle every tank, all winter. This installs once and warms fuel at the pickup on every cold start for years. Many fleets run both: the heater as the built-in defense, additive as backup in the cab.
I already run a block heater. Do I still need this?
Yes. A block heater warms the engine, not the fuel. A warm engine still will not run if wax has gelled the fuel at the pickup or filter. This heats the diesel itself, so fuel keeps flowing while the block heater warms the engine.
Will it leak where the wires come out of the tank?
No new hole is drilled. Two grooved gaskets replace your stock flange gasket and their channels carry the wires out the opening that is already there. Seal that channel fuel-tight and vapor-tight, because diesel can wick up the wire strands.
How cold can it handle? Do I also need a filter heater?
The heater is rated to −40 °F. In extreme sustained cold, pair the in-tank heater with a fuel filter heater so fuel stays liquid from tank to injectors. For most trucks and generators, the in-tank heater is the place to start.
Warranty & support
The Zeus-F3 carries a 12-month limited warranty. For parts, accessories or service, contact us at info@vvkb.com or through vvkb.com. Engineered by VVKB, a cold-start heating manufacturer since 1996.