How dual tank transfer works
In a transfer-style dual tank system, the engine only ever draws from the main tank. The secondary tank is a reserve, and a separate transfer pump moves fuel from it into the main tank when the driver asks. Some systems also have a solenoid valve in the transfer line and a dash light that shows when fuel is moving.
The Elite's Dual Fuel Tank Transfer function manages all of it. It can drive the transfer pump, a control solenoid and a status light, and it can read a transfer request switch, the main tank level and the secondary tank level.
Wiring tab options
Transfer Request Mode
This decides how the driver's button behaves:
- Transfer while active: fuel moves only while the button is held (or a toggle is on). Let go and it stops.
- Press to Start/Stop Transfer: one press starts the transfer and the next press stops it. Best with a momentary button, and the ECU's automatic stop conditions end the transfer if the driver forgets.
Main Tank Full Source
How the ECU knows the main tank has room left:
- None: no full detection. Transfer stops only on the button, time or speed limits.
- Switch Input: a float switch or level switch in the main tank tells the ECU it's full.
- Fuel Level Sensor: uses a fuel level sensor already set up in ESP, and unlocks the Main Tank Stop Level setting.
Secondary Tank Empty Source
- None: no empty detection.
- Switch Input: a switch in the secondary tank signals it's empty so the ECU stops the pump.
Running a transfer pump dry is hard on it, so we recommend some form of empty detection whenever the hardware allows.
Status light and control solenoid
Transfer Status Light Enable gives you an output that lights up while a transfer is running. Transfer Control Solenoid Enable adds an output for vehicles that use a valve in the transfer line. Turn on whichever your vehicle actually has.
Fuel Transfer Settings tab
| Setting | What it does | Our advice |
|---|---|---|
| Main Tank Stop Level | The main tank level where transfer ends. Only shown when the full source is Fuel Level Sensor. | Leave a margin below truly full, so fuel sloshing on a grade doesn't overfill or push fuel into the vent. |
| Max Transfer Time Enable and Max Transfer Time | Cancels any transfer that runs longer than the time you set | Time how long a full transfer takes with your pump, then set a little above that. It's your backup if a level input fails. |
| Max Vehicle Speed Enable and Max Vehicle Speed | Stops an active transfer once road speed goes over the limit. Needs a vehicle speed sensor set up. | Useful if you only want transfers while stopped or crawling. |
A typical setup
Here's how we'd set up a truck with a transfer pump, a main tank level sender and a float switch in the reserve tank:
- Make sure the main tank fuel level sensor is set up and reading correctly first.
- Transfer Request Mode on Press to Start/Stop, wired to a momentary dash button.
- Main Tank Full Source set to Fuel Level Sensor, with a sensible Main Tank Stop Level.
- Secondary Tank Empty Source set to Switch Input on the reserve tank float.
- Status light enabled, so the driver can see when fuel is moving.
- Max Transfer Time enabled as a backup.
A transfer pump draws real current. Drive it through a relay from the ECU output, and fuse the pump circuit properly. The ECU output should only ever switch the relay coil.
Troubleshooting
| Symptom | Usually |
|---|---|
| Transfer won't start | Main tank already reads full, secondary empty switch is active, or speed is over the limit |
| Transfer stops early | Max Transfer Time too short, or the level reading is noisy near the stop level |
| Main Tank Stop Level not shown | Main Tank Full Source isn't set to Fuel Level Sensor |
| Max Vehicle Speed option missing | No vehicle speed sensor is set up |
Related pages
On a Nexus ECU, see dual fuel tank transfer in NSP. For level sensing, see fuel level sensor calibration.
FAQ
Can the Elite read both tank levels?
It can use a fuel level sensor for the main tank. For the secondary tank, the empty detection is a switch input.
Do I need a transfer solenoid?
Only if your system has one. Many transfer systems are just a pump and a line. Enable the solenoid output only when there's a valve to drive.
