Starter

Old cars had those funny cranking handles at the front to get them spinning. Your E30 doesn't. Why not? Because you have a Starter, that's why.

Overview

The Starter is an incredibly powerful electric motor, designed to spin your engine up to a speed that's fast enough for the explosions to take over and drive the engine continuously. If your engine goes below that speed, it will stall and you'll need your Starter to spin it back up again. It's that simple.

It does this by driving a very small cog, known as a Bendix against the toothed edge of your engine's flywheel. This cog is pushed out from the body of the starter when you turn the ignition key by a solenoid; as soon as you release the ignition key, the bendix disengages and the starter shuts off.

The starter unit on all E30s is self-contained and non-serviceable; you can't separate the starter motor from the solenoid or its internal switching relay. Fortunately, there are very few reported cases of faulty starters, and the most common cause of starter motors not working is the wiring.

Components

The starter motor assembly is a one-piece unit, and is not designed with disassembly and servicing in mind. But it's worth knowing what's going in inside the assembly, so here's a run-down.

Starter Motor

The starter motor sits on the side of the engine block, just underneath the intake manifold. It's held in place by two bolts that screw into the gearbox bell housing, and is fed by wires from the engine loom.

The motor itself is a 1.4kW unit, specific to each engine. It needs to be this powerful to kick-start the flywheel into spinning at a speed that will allow the engine to run from its own combustions.

Solenoid

Since the starter motor needs so much power to get moving, it would be dangerous to run that sort of current through the ignition switch. So the motor is switched by an internal solenoid; a simple relay that uses the signal from the ignition switch to activate the more powerful motor.

When your Battery is flat, it will be the solenoid that you can hear clicking from the engine bay if the starter isn't spinning. However, if you don't even hear clicking, don't suspect that the solenoid is at fault; E30 starters are surprisingly robust, and solenoid failure is extremely rare.

If you do suspect a faulty solenoid, then unfortunately you have to replace the entire starter, as it cannot be disassembled.

Bendix

The Bendix is a special cog mechanism that allows the starter to engage with the engine flywheel. It's designed to move in and out of the starter when needed; if it didn't retract after the motor starts the engine, then the flywheel would be driving the starter which would ultimately burn out the motor.

Therefore, the Bendix is both a cog and an extending mechanism. The cog itself is specific not only to the flywheel but to the age of the vehicle; facelift engines have different flywheel teeth to pre-facelift cars, and therefore the Bendix must be different to match.

Wiring

Your engine loom will have four wires. What's more, an E30 facelift motor should have two 8mm studs, one 6mm stud and a 5mm one. The common mistake is that the four wires go to a different nut each. Not so. Here's how it's wired.

• The small green/black wire goes to the 5mm stud at the top of the starter
• The thick red and thick black power cables go to one of the big 8mm studs; the one on the "outer" side of the starter, away from the engine block. These should connect to the alternator and battery respectively.
• The thick black cable goes to the 6mm stud at the bottom of the starter.

Green/black goes to the unloader relays and provides a signal causing them to drop out when you are starting the car. The other smaller wire on the solenoid is the one that provides the power to pull the solenoid in.

Common Problems

Many people jump to the conclusion that if the engine won't start then the problem must lay with the Starter. They then go to the massive trouble of replacing the Starter, only to find that their problem persists.

Before you even consider swapping your starter, it is essential to try starting the engine using the Diagnostic Plug. This will determine whether the fault is with the starter, or the starter signal. If the starter spins from the diagnostic plug but not from the ignition key, then the problem is with the black or black/green wire, or the ignition switch itself.

If the solenoid is clicking but not engaging the main motor, and it is receiving good power and grounding, this indicates two possible problems. Either the actuating arm that pulls the starting gear is sticking, thus not allowing the big terminals within the starter solenoid to make contact and activate the motor, or the solenoid itself is faulty.

If your Starter refuses to spin, and you're certain that the Battery is not to blame, then you need to check the thick power cables from the starter to the battery, that all the connections are tight and free of corrosion, and that the earth straps from the battery to the car body, and from the car body to the engine block, are also connected properly.

If you are confident in your cables, pull the starter out and make sure the lever and gear are moving freely, add some waterproof grease if necessary.

Testing

Test the solenoid by grounding it and supplying power to the #50 (black/yellow) terminal and then test if you have continuity across the 2 large terminals. Preferably connect something that has a large current draw across the terminals to ensure that this continuity is capable of transferring a large current.