Problems With Pre Engaged Starter Motors

Problems With Pre Engaged Starter Motors

This guide captures ‘bygone’ advice on Problems With Pre Engaged Starer Motors. It is part of a series I am building on Starter Motor Problems 

To see all my ‘bygone’ advice guides please visit Classic Car Maintenance DIY Guides.

Remember folks these are ‘bygone guides’ … useful but the safety and personal protective equipment measures are reflective of bygone awareness. Stay safe.





Common Starter Motor Problems

Below is a quick diagnosis chart for most common starter motor problems. All of which will be covered in detail within Starter Motor Problems .

Common Starter Motor Problems

Problems With Pre Engaged Starter Motors.

A pre-engaged starter is easily recognized because it carries a solenoid housing upon its back (see below). This solenoid actuates a lever which pushes the drive pinion in to mesh with the flywheel ring gear. It is not until this happens that the starter motor begins to turn. Hence the name, pre-engaged.

Exploded Diagram Of A Pre Engaged Starter Motor

A Loud Click ?

Having also checked that the battery is not faulty, listen for a loud click when you try to start the car’s engine. This click is the solenoid operating, indicating a jammed starter motor.

No Click ?

If there is no click, trace the wire from the ignition switch to one of the solenoid terminals (see below), and connect a voltmeter between it and earth. When the starter switch is operated a 12-volt reading should show. If not the fault lies with the lead or the switch.

Testing a Starter Motor Solonoid Switch Test 1
When starter switch is operated the voltage shown here ( 6v or 12v depending on your battery) would indicate that the supply is OK but the solenoid windings are faulty

A reading taken from across the two solenoid points should also give you 12 volts (see below). If not, check the main cable or expect a faulty battery, a condition you could have checked by trying out the head-lights previously.

Testing a Starter Motor Solonoid Switch Test 3
To check the switching contacts, connect up the voltmeter as shown. The battery voltage shown should fall to zero when the solenoid is operated for the switching contacts to be serviceable

With the ignition still on and the correct reading being shown on the voltmeter, have a second person turn the starter switch.

The voltage should drop to zero.

If not, the solenoid switch itself needs replacing.

If the voltage drops and the starter motor still refuses to turn, then it must be removed and inspected.

Disconnect the battery earth (ground) cable and also the cables from the starter solenoid switch.

A new solenoid may be fitted over the existing plunger once the securing nuts have been removed. There are usually two on fixed through bolts.

To dismantle, remove the three mounting bolts and lift off starter. Clean and check the flywheel ring gear for wear. Disconnect the field winding cable from the solenoid and unscrew the solenoid retaining screws and lift off.

Solenoid Replacement on Starter Motor Pic1
Remove starter motor. Now disconnect field winding cable from rear of starter solenoid
Replace Starter Solenoid
Remove the solenoid retaining screws or the two through bolts sometimes fitted
Remove Starter Solenoid
Pull solenoid away from starter drive and cover. If only the solenoid is faulty. it can be removed at this stage

Remove the through bolts from the rear end of the motor. Withdraw the drive gear housing and unscrew the engaging lever guide screw.

Remove Starter Solenoid Motor Casing
Unscrew the through bolts at the rear end of the motor casing and remove the bolts
Dismantling Pre Engaged Starter Motor
Withdraw the drive end gear housing. On some starters you have to unscrew the engaging lever guide screw (arrowed)

Remove the rubber and steel washers from the drive end frame and then remove the armature complete with the engaging lever out of the frame.

Remove Starter Motor Armature
Remove the armature. Examine teeth of starter drive pinion (arrowed) for wear. Replace if necessary

Instead of the inertia return of the Bendix drive the pre-engaged starter relies on a roller clutch to return the pinion drive down the shaft once the engine starts through the lever, operated by the solenoid.

To remove the pinion and so the clutch, first ‘drive the thrust collar down the shaft towards the pinion. This can be done with a piece of hollow tube. Displacing the thrust collar reveals a circlip or a jump ring and this must be removed and set aside safely.

A worn driving gear should be renewed. Check the roller clutch by seeing that it turns freely in one direction and takes up the drive of the shaft in the other while sliding freely up and down the shaft.

Check Roller Clutch on a Starter Motor
Check the roller clutch for correct action. While sliding along the shaft, it should turn freely in one direction only

It will do no harm to clean up the commutator faces with fine glasspaper although take care not to damage the insulation.

Examine The Commutator on a Starter Motor
Examine the commutator for wear. Clean with spirit soaked rag and fine sandpaper. (Inset is a worn commutator)

If the clutch operating lever has been removed it may be necessary to fit a new pivot pin.

Unscrew the two screws of the bushing protective cover at the commutator end.

Dismantling Pre Engaged Starter Motors
Remove rear end bush cover and shims and remove U clip. Keep everything in the correct order for re-assembly

Remove the small cover and any shims and seal rings. Remove the commutator end plate with its brush assembly. Examine the brushes for wear.

Brush Assembly on Pre Engaged Starter Motor
Ease away commutator end plate to expose brush assembly. Renew brushes if less than 10mm ( 3/8 in) long

Worn brushes must also be renewed.

With a four brush set two will have to be soldered on to the field coil.

If your motor’s field winding is pressure soldered take care to retain a bit of the old brush copper wire as the new brush will not solder directly to the terminal.

Fit New Brushes to a Starter Motor
Field winding brushes are pressure soldered to their posts, cut leads -¼in. from posts and solder new brushes to these tags

Check that all brushes move freely in their bores after thoroughly cleaning. If not ease with fine file. Check also that the brush springs have equal and adequate pressure.

Check Starter Motor Brushes
Check brushes move freely. If not use a fine file to ease them. Check brush springs for equal pressure.

If there is any visible movement from the armature in the two end bushes, these should be renewed. If they are of the phosphor bronze type they must be soaked in engine oil for 24 hours before fitting.

When the motor has been re-assembled, it is always wise to connect to the battery before re-fitting, just to make sure it is running. Only run it briefly to check.


What Next ?

Head over to my starting page on Starter Motor Problems to select the next section.


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