Hesistant Starting Diesel

[StephenW]

I have a Vetus M3.10 3 cylinder 20 hp diesel engine in my boat and when starting it there is an occasional delay between pressing the starter motor button and the motor actually turning the engine. Once or twice it has required 2 pushes to get it to turn over. Believe the engine is based on a Mitsubishi K3D tractor engine and marinised by Vetus. The engine has been first rate when running

Any ideasas to why there should be a delay or requirement for 2 pushes of the starter button? My first thought is maybe some form of loose connection at the battery or in the circuit - any other suggestions?

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[boatless]

Primary cause is poor connections on the battery or engine ends of those same cables, as you correctly guess. You should be able to hear a faint click from the starter solenoid when the starter fails to turn, which tells you that it would like to close the contact, but can't quite make it.

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[AndrewB]

The two suspect items here are the solenoid and the starter motor. As Boatless says, if you reliably hear a click when the ignition is turned, the solenoid is probably OK. It is usually pretty reliable, but the low current (thin) connections between it and the ignition switch may work loose.

A starter motor can get gummed up so that the gear doesn't readily engage, to the point that it needs a tap to get started. Cleaning it is not a difficult DIY job. As you suggest, the high current (thick) connections between battery, solenoid and starter motor should first be checked to make sure it is getting a good supply of power.

 

[Jools_of_Top_Cat]

Actually there are three items that could be suspect here,

the starter
the solenoid
the switch

4 including the ignition barrel.

I would be least likely to suspect the starter at this point as when it does spin it works, I would expect it to be either dead or alive not in a transition state.

The solenoid, this is highly suspect, they do not last forever, although can be repaired if you are prepared to shove pieces of metal in to replace burnt of solenoid contacts.

The switch is something I would look for first here, it is all low tension so a test bulb or multimeter would be fine, get someone to press the button and see if 12v appears at the LT contact of the solenoid, if not then check the contacts on the switch and that the switch is getting a decent +12v from your ignition barrel.

hope this helps

p.s. One of the problems with high power DC is its tendency to arc, this is why solenoids do burn away after time. Even your switch conacts with very little current will arc each time you press it, getting at the contacts with wet and dry will usually help matters. Although from experience, once you have to start cleaning contacts in this way you are starting a losing battle and will be cleaning annually and then at shorter periods until it is time to replace. The favourite items that fail on cars are sunroof and window switches.

I shall stop before I bore you to death.

<hr width=100% size=1>J

<A target="_blank" HREF=http://www.topcatsail.co.uk>

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[AndrewB]

Just my luck to be plagued with dodgy starter motors then!

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[VicS]

I'm with Julian on this one.

Go for the starter button first. If the connections on the back of it are easily accessible you could try just shorting across them to see if things operate normally.
If it is the button it might cure itself as the season progresses.

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[boatless]

Please do tell us who was right!

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[StephenW]

Many thanks for your thoughts guys
Stephen

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[Bodach na mara]

Nobody seems to have mentioned the earth return. I have had similar problems on several cars and it always came down to poor earth continuity, either due to duff connections at either end or in one case to a corroded core in the cable. Check the voltage between engine block and battery negative (assuming negative earth) while operating the starter. It should be very low, certainly less than 1/2 volt.

<hr width=100% size=1>Ken Johnson

 

[William_H]

For a completely different slant on this problem. Some starter motors on vehicles use the solenoid to push the pinion gear into the ring gear on the engine before making contacts to switch power to the starter motor. If the sliding spline drive becomes corroded or sticky the pinion won't move and so no contacts are made. The effect is that even with ok electrics clunk may not be heard. If you remove the starter you will find the pinion ie drive gear should be free to slide against a spring towards where the engine ring gear would be. ( Just to explain most starters however put electric power onto the starter motor first The pinion gear slides on a spline which is spiralled so that the enertial of the gear causes it to slide into mesh with the ring gear. The disadvantage is that the pinion can be turning when it engages the teeth of the ring gear causing wear and noise.) Your starter may be the former type. The solenoid is a cylinder about 40mm diameter 50mm long with bolt connections of the heavy cable from the battery. If it is mounted remote from the starter it is obviously not the type I describe which pushes the pinion but if it is mounted on the body of the starter it may be. Regards ole will

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[brianhumber]

Re: Be methodical

How old is your installation.
Have had similar fault to yours, but in going through the systems as per other threads because my pride and joy was 15 years old minor defects were found on most items. Finally got rid of this when I rewired from the cockpit starter switch to the solenoid on the starter motor. The old small gauge wires had oxidised over the years causing higher resisitance and volt drop.
Moral of the story is on an old yacht you must start with the easy items and work your way through the system, correcting as you go.

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[GrahamSC]

Re: Be methodical

Hi
Just another link in the chain. If there is a battery isolating switch.( the one with the red removable key) there is a possibility of high resistance under load on the internal switch faces that can cause this. I spent a lot of time wondering why the lights and radio worked but the starter only clicked. New switch sorted it.
Regards
GRahamSC

<hr width=100% size=1>Never recovered from loss of Tot, 1974

 

[TonyBrooks]

Re: Be methodical

I am sure this ehgine has a pre-engauge startser - the one with the solenoid on top.

1. Ensure battery is well charged and in good condition.

Identify where the thin wire from the ignition switch is connected to the solenoid.

2. Multimeter set to 20V dc between battery pos and the part of this connection that is on the solonoid (not the female cable terminal)

Meter should read battery voltage - ignore this

Operate starter. If meter reads much more than about 0.25 volts then you have some form of bad connection, too thin a cable, faulty ignition switch contcats.


3. Multimeter still set to 20V dc between battery pos and the cable/copper strip that joins the solnoid to the actual starter motor.

Meter should read battery voltage - ignore this.

Operate starter ( may ahve to use stop to prevent engine starting), meter should read less than about 0.5v. If it reads more you have a problem. My guess is that it will probably read battery volatge when the starter plays up.

If it reads more than 0.5v put multimeter between the two big, nut type terminal on the solonoid & operate starter. Again if this reads more than about 0.5v the solenoid contacts are burnt (my no.1 suspect) change solenoid or strip end cover if of a type that allows stripping and clean/renew/turn over the copper parts.

If that is not the cause of the voltdrop, look for bad joints where the starter cable is crimmped into the terminals, loos or dirtty connections, undersized cable - should eb about fingure diameter.

4. Meter between battery neg and either starter body or where negative cable is connected to starter.

Meter shoudl read zero volts - ignore this.

Operate starter, using stop if required to prevent starting. Meter should read less than 0.25v. If its more than this look for bad crimps, loose/dirty connections and undersized cable.


Having made sure the solenoid contacts na dwiring is servicable, my no.2 option would be a sticky pinion or solenoid armature as described in other posts.

Hope this helps

Tony Brooks

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