Freefall lifeboat engine does not start. Part 2. Troubleshooting

Greetings! Today we have another problem with the lifeboat, it won’t start with any battery. At the same time, you can hear the starter motor rotating, but the start does not occur. This is the second article on this topic. In the first article we looked at a case where one battery failed and in that situation the battery tester was very helpful in identifying the problem.

In fact, low starter battery capacity is a fairly common cause of poor starting of lifeboat engines. Usually the solution to the problem ends with this, that is, replacing the batteries. But there are exceptions, especially on older ships.

And in this article we will look at one of these exceptions.

Checking battery capacity using a battery tester

The photo above shows that the battery capacity is fine.

Of course, it is better when the ship has a special electronic battery capacity tester, but such battery tester is also suitable for starting batteries (only an electronic tester is allowed to be used on tankers).

Lifeboat engine

As a rule, if there are no problems with the batteries and the boat does not start, then before disassembling the DC starter motor, it is necessary to check all cable connections according to the diagram. You also need to check all starter battery selection switches and contacts on the ignition key mechanism.

Starter diagram of the engine and auxiliary equipment of the boat

Checking and renewing cable connections (1)

Checking and renewing cable connections (2)

Despite the poor condition of all connections on the sensors and terminals (the ship is more than 10 years old), no significant problems were found here. The only problem that was identified was the unstable operation of the oil pressure sensor, which generates an alarm about low oil pressure before starting the engine.

Low oil pressure (light on)

Low oil pressure (buzzer) (video)

The next step is to check the DC starter motor. In the diagram, the starter is indicated as Starting Motor.

In this situation, when you turn the ignition key, you can hear the starter motor working, you cannot hear the click of the relay gear ejecting the gear to the flywheel of the engine crankshaft, and this actually hides the problem.

What is the toothed gear (Bendix)?

The starter consists of two main elements, this is the electric motor itself and the Gear retractor (throwing out) relay, that is, the toothed gear, which, due to the flywheel, engages with the engine crankshaft and thus spins the engine itself.

Why a pull-in (kick-out) relay and not just a pull-in relay? Because the coil pulls in the core, but at the same time throws out the gear.

How does a starter work?

When 12V is supplied to the starter (the negative is supplied to the starter housing), the bendix ejection relay (coil) receives power, the core is retracted and the motor stator receives the plus through the pressure plate. Thus, the gear is thrown out, meshed with the flywheel, the starter and, accordingly, the engine crankshaft are spun. All these actions occur almost simultaneously, visually it seems that first the bendix is thrown out, then the engine spins up (the video will demonstrate it clearly).

Diagram of the operation of the starter and Bendix relay (on the left - without power, on the right - with power)

In our case, it is necessary to disassemble the starter and check how it works. When removing the starter, you also have to remove the belt and alternator.

It is advisable to disconnect the batteries first! You also need to mark all disconnectable cable connections.

Removing the belt and alternator

Removing the generator

Starter Motor

Removing the diode and voltage regulator

Removing the starter (the bendix relay is mounted on top of the motor) 

As a result of removing the starter, it was discovered that the bendix (the toothed gear) was stuck to the motor shaft due to heavy rust and thus the electric motor spun, but the gear did not eject.

Disassembling the starter motor (1)

Disassembling the starter motor (2)

Disassembling the starter motor (3)

The photos above show how rusty the gear and shaft are. Of course, in this state the starter will not work. The mechanism has been carefully serviced, all moving elements have been cleaned, adjusted and lubricated.

Disassembling the electric motor

The electric motor was also disassembled, the brush apparatus, bearings and stator winding were checked. No defects found.

Checking the bendix relay (coil) (1)

Checking the bendix relay (coil) (2)

The Bendix coil was also checked using the tester. Slightly incorrect photos, need clarification.

Resistance 0.57 MOhm is the resistance between the contacts of the plate, which is currently open. It is along this plate that the plus is transferred from the coil to the motor. Those, when power is supplied to the coil, it retracts and the plate is pressed (there should be 0 Ohms between the contacts), and then the electric motor receives power. The video at the end of the article will clearly show how this happens.

Resistances of 369 kOhm and 0.426 MOhm are attempts to measure the resistance of the coil itself. I could be wrong here, because writing an article and practicing are very different in time. I can’t say definitely what the resistance of the relay coil should be.

Checking the operation of the bendix relay using a battery

There was an incomprehensible situation with the coil, so we decided to test it using an old (working) battery. There is a minor error here, although not of much significance. Plus was connected to both contacts of the plate (the plate is not visible, it is inside), but when checking the coil, this does not affect the retraction of the core in any way.

The test gave a positive result, the relay is working.

By the way, pay attention to the shape of the core head and go back to the photo “Disassembling the Starter Motor (1).” This shape is necessary to engage the core with the ejection mechanism.

When the coil retracts the core, it uses a mechanism to throw the gear (Bendix) forward, but the plate inside (there is no access to it) is pressed.

After starting the boat engine (ignition key in zero position), the coil and starter lose power, the bendix leans back (thanks to the spring) and the starter stops.

Checking starter operation using a battery

The starter was fully assembled and tested in operation (video at the end of the article).

Generator disassembly (1)

Disassembling the generator (2)

Minor work has also been done on the generator - the grease in both bearings has been replaced.

As a result, everything was assembled and tested in operation. No remarks!

Background. This problem did not happen immediately. Arriving at the ship, my colleague said that the lifeboat was starting poorly, and he replaced the batteries with new ones, and also renewed all the contacts on the starter. It turned out that the contacts were renewed not on the starter, but on the generator.

This story lasted from six months to a year, I couldn’t find out exactly. The lifeboat had prolonged starts and it is clear why. At the same time, the lifeboat could start at the third time, which is not good. But the boat was started and the crew believed that the problem was not critical.

Checking the bendix operation (video)

Checking the operation of the lifeboat engine starter (video)

I started the article with the fact that the boat won’t start. This is what happened in the end, and therefore I had to disassemble the starter.

Conclusion. Do not confuse the “starter” and “generator” - these concepts are different things ;)