Denso HP2 Pump

7 July 2014  

The two pumping chamber’s pistons are set at 90° to each other so that they are on opposite strokes but are operated by the same cam. In the image above, Chamber 2 is on the intake stroke; fuel from the internal feed pump enters the chamber via the check valve when the SCV is open and forces the pistons apart. The amount of fuel entering the chamber is controlled by how long the SCV is open during the intake stroke.  A short opening time will only partially fill the chamber, by moving the pistons out a reduced amount so that the rollers do not touch the cam. This means the cam has to turn until the rollers touch the cam and start the outlet stroke.

The amount of fuel delivered to the common rail is a function of the angle through which the rollers are in contact with the cam – shaded red in the image below. Both the contact angle and the common rail pressure are parameters on your scan tool; the relationship between engine speed, contact angle, injection quantity and common rail pressure are monitored for plausibility.

Pump Timing

What goes wrong?

Symptoms of SCV failure

Checks