Ask The Mechanic – Starter Motor

My starter motor does not always engage

Check the Body (Chassis) to Engine (Drive unit) Earth braid, it is 6″ min. & 8″ max long. It is situated underneath the vehicle at the N/S rear, from the diagonal arm axle mounting bracket to a gear casing bolt, (best to replace this braid anyway!)

Also check & clean the following points: –

  • Battery un-insulated braid to body (earth)
  • Battery un-insulated braid to battery (-) Negative post
  • Battery cable to battery (+) Positive post (a 25 mm2 thick black insulated cable) this connects to
  • Starter motor solenoid (connection 30) (this is a ring terminal on a bolt)
  • Starter motor solenoid (connection 30) also has a ring terminal connecting to a 6 mm2 wire having red with white tracer insulation. This connects via a push on ‘250 Faston’ terminal to
  • Fuse box (fuse No. 9) (a brass link joins this to fuse No. 8) so from
  • Fuse box (fuse No. 8) has a push on ‘250 Faston’ terminal connecting to a 4mm2 wire having red insulation. This connects via a push on ‘250 Faston’ terminal to
  • Terminal black ‘T4’ (which has a through connector) so from the other side of
  • Terminal black ‘T4’ a push on ‘250 Faston’ terminal connected to a 4mm2 wire having red insulation. This connects via a soldered connection to
  • Ignition switch (connection No. 30) so from
  • Ignition switch (connection No. 50) a soldered connection to a 2.5mm2 wire red with black tracer insulation. This connects via a push on ‘250 Faston’ terminal to
  • Terminal block ‘T4’ (which has a through connector) so from the other side of
  • Terminal black ‘T4’ a push on ‘250 Faston’ terminal connected to a 4 mm2 wire having red with black tracer insulation. This connects via a push on ‘250 Faston’ terminal to
  • Starter motor solenoid (connection No. 50)

Approximate length of wire between E and N is 13 mtrs varying from 2.5 to 6mm2. Between A and N + starter flange, soldered internal, crimp joints, riveted and loaded switch there are 42 connections and these cause voltage drops!

NOT ALL OF THEM ARE SERVICEABLE!

That is an awful lot of cable to navigate. Next time, we will look at simplifying this with a hot start relay system that can be installed in about 30 minutes.