Fuel Pump Priming Timer
for vehicles with
BOSCH L-Jetronic Fuel Injection
(Fully Assembled Module)

Product Use

This 12 VDC Timer Module is especially developed for Automotive use.

It is intended to be used on all vehicles with BOSCH L-Jetronic Fuel Injection System.

The 12 VDC Timer Module primes the Electronic Fuel Injection System (EFI) to full fuel pressure prior starting the engine, and this allows easy and instant starts no matter for how long the vehicle was parked or if it is hot or cold.

The BOSCH L-Jetronic Fuel Injection System as originally designed only switches on the Electric Fuel Pump once the Fuel Injection Control Unit senses "Air Flow" signal from the Air Flow Meter.

Also the BOSCH L-Jetronic Fuel Injection Systems Fuel System is designed to "hold" Fuel Pressure (usually at about 36 PSI) when the engine is turned off.

On older vehicles, or vehicles that have been parked for extended period of time, this Fuel Pressure is eventually "lost" and this makes the starting more difficult, especially at temperatre extremes both hot or cold.

When "Ignition ON" signal at a typical automotive system voltage (10 VDC to 14.4 VDC) is applied to the 12 VDC Timer Module the Output is automatically turned ON for pre-set time interval through a high current Relay, and then goes OFF for as long as the "Ignition ON" signal is applied.

The 12 VDC Timer Module is used to provide power signal (12VDC +), which is used  to prime the fuel pump when Ignition switch is first turned on and before the engine is cranked to be started.

There are two Status Indicator LEDs located on the Module:

Yellow LED is ON when the "Ignition ON" signal is supplied.

Green LED is ON when the Electrical Fuel Pump is powered.

Internally the Timer is connected directly to Control Input of the 12 VDC Relay Driver,  which in turn controls an electro-mechanical Relay with 10A power contacts.


Click on image to see enlarged image.

Fuel Pump Timer Module Schema



  1. Vbb = 12 VDC + Battery (connect through 15A fuse)
  2. Ign (Ignition ON Signal 12VDC +)
  3. OUT = To Fuel Pump +
  4. GND (Common System Ground)

Product Specifications

Power Supply Voltage (min/max) VBB 8 / 16 V
OUTPUT Load current (max) IL 10 A
OUTPUT Signal Voltage (min/max) VOut VBB - 0.25 V DC
Power Consumption (LEDs) Pon 160 to 210 mW
Operating Temperature Ton 20 to 140
-6 to 60


US $46.50 each

Inquire for pricing and availability on purchases of 100 units or more


This Autotronic Module can be used in any of the following vehicles with BOSCH L-Jetronic Fuel Injection:

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