Injection pump pressure regulator spring

[dave friday]

Morning all, as above, should the spring be under pressure from the plunger,i have two and they both rattle [when shaken up and down]
although they seem to be set differently as the engine note changes and the amount of power, depending on which one is fitted.
Ta.

[410]

The spring rattle is normal.  What matters here is the internal fuel pressure in relation to rpm.  The spring that's rattling inside the regulator gets tension on it from the piston as soon as the pump starts building pressure.  The lug on the end of the regulator that you can see when it's threaded into the pump is what adjusts the internal pressure in the pump.  Push that lug in and the internal pressure goes up.  It takes very little movement of that lug to increase the pressure.  It can be backed off by removing the piston retainer clip, piston and spring and tapping it back out.  If you don't remove the piston and spring when trying to back the lug out, the spring gets damaged and changes the pressure curve in a bad way.

One final note, internal pressure is directly related to dynamic advance.  Internal pressure goes up, fuel timing advances.

[dave friday]

Thanks 410,your reply answers my question completely.