Electrical Consideration Relative to Engine Starting
May 1st, 2008A lot of things can contribute to hard starting engines that are electrically related. Assuming that the internal workings of the engine are as they should be, we will look at the electrical problems that relate to starting. We will stay away from charging and electrical ignition circuits for now.
The starting battery(ies) must be in good condition. Once a battery used in the marine environment gets three years old, it should be considered suspect. Most batteries have a life curve that stays relatively flat in the beginning, starts slowly down for a short period and then drops dramatically towards the end. An engine that ordinarily starts promptly can get by with a battery in the declining portion of the curve. However, if a battery being used beyond the flat part of the life curve is called on to do a little extra work, it can fall flat. Extra work would fall in the category of colder temperatures, recovering from a fuel outage and other reasons for something other than a quick engine start.
The starting motor must be in good shape. Starters have moving parts that wear, bearings that need lubrication and electrical components that build resistance to electrical flow. Usually starting motors are used until they fail completely. To preclude this spurious failure, preventive maintenance is required. How often a starter should be rebuilt is hard to say. The interval relates to how much the starter is run. If the engine typically starts right up, the starter only runs for a second or two for each use. If the starter is required to run for longer intervals because of reasons not internal to the starter, the time-in-use can rise dramatically. Starter performance usually decays slowly so that diminishing performance may be hard to recognize. The starter solenoid must be in good condition and have the battery cable and the connection into the starter motor clean and secure. The solenoid actuator wire must have clean connections and be firmly affixed at the solenoid. The solenoid has a contact plate internally and it can sometimes get contaminated to a point that it will not reliably make the connection. This is usually the case when the solenoid clicks in but nothing else happens. The same symptom can indicate bad or sticking brushes in the starter motor itself or poor battery cable connections.
All wiring must be of adequate size, in good condition and properly connected at the ends with all connections clean and tight. Tight by itself does not count. Good contact requires intimate contact of the surfaces within the juncture. Oxides build up over time that result in poor contact and increased resistance in the circuit. This resistance will reduce the current carrying capacity and the efficiency of the circuit. Oxides must be removed by undoing the juncture, cleaning the wire end and the surface to which it will be reinstalled and then reconnecting tightly. Spade terminals sometimes need to be pinched closer to assure a good connection. Switches in the circuits can oxidize resulting in voltage drop. Wire conductors, inside the insulation, can corrode and lose area resulting in lessened current carrying capacity. Wires that are too small, corroded or badly connected can sometimes be detected by feeling for warm spots.
A frequent cause of electrical problems can be found in the harness connectors. These connectors are there because it made installation of the engine more simple when the boat was built. The engine was installed with a connector, the instrument panel was installed with a connector and then the harness was plugged in between them. The pins and sockets in these connectors oxidize over time and the resistance increases until intermittent problems arise and can get worse to the point of melting the connectors and to even starting a fire. Removal of these connectors is highly recommended. Cut off the male and female connectors and reattach the wires using crimp butt connectors, preferably with heat-shrink insulating tubes, or soldering, again with heat shrink applied. Quite often several feet of wire can be eliminated with this operation which also improves electrical function.
Starter switches can be push button or key turn but they all have contacts that can oxidize. The usual repair is to replace the offending switch. Isolating switch and/or electrical problems away from the engine can be done by shunting the starter actuating circuit directly at the starter solenoid. This can be crudely done by sticking a conductor (usually a screwdriver) from the battery wire terminal at the starter to the starter wire terminal adjacent to it on the starter. Push button remote starter switches with alligator clips and a push button can be clipped to the same points. This can be left connected and when a malfunction occurs can be used to bypass all the other stuff and possibly isolating the area of the trouble. If use of the bypass push button doesn’t make the starter turn, the problem is in the solenoid or the starter itself.
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