Engine won't crank if recently cranked

[JimZeigler]

Classic symptoms of corroded connection. There is corrosion somewhere in the high amperage circuit that heats up and bullds resistance when it is used. The resistance decreases after it cools.

You need to clean both the positive and negative connections in high amperage side of the starting circuit. Start from your battery and follow every connection to the starter, both on the positive and negative side. Clean these connections and apply dielectric grease. On my boat, the negative pole of the battery is directly connected to the engine block and there is a separate negative connection from the starter to the engine block. Clean and lubricate both. If you have a battery switch in the positive circuit, make sure you clean the connections to that switch.

[Bycrick]

Slide-on, otherwise called spade connectors or quick-connects work (when they work) by the springiness of the metal of the female side. Eventually, the copper looses the spring and you get a loose connection. Temperature cycling only makes it worse. Trying to squeeze the connector to tighten it is useless, except in an emergency. Just replace it.

[Dieseldude]

Originally Posted by Ryban

I'm pretty sure this is a battery or weak connection issue, but wanted to get some feedback to help me debug this week.

My Vetus M4.14 will always start, but has a few concerning quirks:

1. If the engine hasn't been recently run, I'll use the glow plugs for 10-15 seconds, but have to wait an equal amount of time before I can start cranking the engine, or I'll just hear a click of the solenoid, but no motion from the starter motor.

2. If I have been cranking to say, bleed the fuel lines (self-bleeding), for a short duration, I need to wait a good 20-30 seconds before I can start cranking again, or again, I just get click of the solenoid.

I suspect this is because whatever voltage the starter motor is seeing, it's below some threshold and it's not getting the power it needs.

I have two battery banks, one made up of 4 x 6V batteries and the other 2 x 6V batteries. They can be isolated, but I've experienced these issues with both banks combined. I'm not sure if I've actually isolated them and troubleshooted, because even when they are isolated by the main switch, there is a switch in the charging circuit that will combine them when they're being charged (which has been most of these times).

It could also be corrosion in the wires or on the terminals, so I'll check and clean everything when I'm back on the boat. I'll also do some voltage drop checks to see if I can narrow it down.

If it's not any of those things though, where else should i look?

Since the problem appears immediately after presenting a heavy load, there is a good chance that the batteries are weak. After a lead acid battery is drained of charge sufficient for starting, it may recover slightly after a short time. So it would be wise to test the batteries. A simple voltage test should show over 13 volts. If they have removable caps, a hydrometer test should be done.


If battery is good, you probably have a high resistance in the starter current path, Check all connections for corrosion and slack terminations from the battery positive to the solenoid and starter. Do not forget the ground connection from battery negative to the engine block. Also, the internal solenoid contacts could be burned, so these should be examined. If badly burned, replace solenoid. But if solenoid contacts are burned,The starter itself could be on borrowed time, so perhaps better to overhaul or replace entire starter.



The starter could have the brushes worn all the way down. If so,the starter will intermittently fail. This can only be determined by opening the starter for a look inside. If brushes are wore down to their limit, trying to run the starter too many more times could melt the copper commutators, and then the starter would longer be repairable. I once had a starter melt its commutators due to extreme brush wear.


It is also possible that the ignition switch contacts, or if equipped, starter relay contacts are burned. This problem can be ruled out by jumpering the solenoid terminals. If the starter will turn upon doing this,the problem is in the ignition switch or the starter relay, or associated wiring.

[David Mathis]

It sounds like you have enough battery power to crank an 8+ liter diesel in cold weather so changing batteries is not the best place to start. Are the connections clean and tight? Checking the cables is cheap and easy. Look at the ends - any corrosion? Now bend the cables to check for internal corrosion - any stiffness or crackling sound? If so replace them; if not, the starter would be the next place to check. Many years ago, a gas engine was acting the same as yours, started great when cold but wouldn't turn over when warm. The starter was changed and the problem went away.

[Dieseldude]

Originally Posted by David Mathis

It sounds like you have enough battery power to crank an 8+ liter diesel in cold weather so changing batteries is not the best place to start. Are the connections clean and tight? Checking the cables is cheap and easy. Look at the ends - any corrosion? Now bend the cables to check for internal corrosion - any stiffness or crackling sound? If so replace them; if not, the starter would be the next place to check. Many years ago, a gas engine was acting the same as yours, started great when cold but wouldn't turn over when warm. The starter was changed and the problem went away.

Yup, a warm engine can possibly be more difficult to turn. With thermal expansion, the piston to cylinder wall clearance is tighter. The rings will seat tighter. This would result in higher compression and more turning power demanded from the starter. Anyone who has run a small diesel with a hand crank for starting knows about decompression valves that need to be opened to be able to turn the thing by hand. They must be closed once the engine is started. A lot of life boat engines have hand cranks and decompression valves.

[Simi 60]

Originally Posted by billgewater

b) purchase a 12 VDC 30 Amp relay and wire it up to provide power to the starter solenoid positive connection. Mount it as near as possible to the starter solenoid. The switching circuit from your starter switch operates the relay and as the relay internal switch only requires milliamps to operate then any poor wiring in this circuit becomes essentially irrelevant.



The installation of a relay right next to the starter solenoid is a fairly common occurrence. These relays are only a few dollars and use standard slide on wiring contacts. They also usually have a replaceable 30 A fuse built in. The larger 60 Amp relays are generally overkill and, usually have two bigger nonstandard connections and usually do not have an inbuilt fuse.
The common 30 A relays usually have the high switched current standard terminals at right angles and opposite to each other and the terminals that you run from the starter switch and the chassis earth are opposite each other and parallel, but check with the retailer.

The wiring from the positive engine terminal (usually right next to or even on the starter solenoid) through the relay then to the starter solenoid should be able to handle the required solenoid current. This current is usually between 10 and 20 amps depending on the size of the solenoid itself. For your engine it may well be considerably less.

If there is no discernible voltage across the starter switch or a drop at the solenoid then the problem sounds suspiciously like an unhappy starter motor or the solenoid internal contacts may be in need of some TLC.

My electrician mate tells me this problem is common because boats often have long wiring looms, which, along with salt air is a recipe for wire and switch corrosion etc.

Oh yes. These 30 A relays are often cheaper than a new starter switch - depending on your access to OEM parts that fit.

Just had this exact thing done to our Genset
Displaying similar faults to the OP - on ours it was plenty of crank but solenoid wouldn't activate.
And you are correct, small money and a six year issue is gone.

[Wotname]

Originally Posted by Dieseldude

Yup, a warm engine can possibly be more difficult to turn. With thermal expansion, the piston to cylinder wall clearance is tighter. The rings will seat tighter. This would result in higher compression and more turning power demanded from the starter. Anyone who has run a small diesel with a hand crank for starting knows about decompression valves that need to be opened to be able to turn the thing by hand. They must be closed once the engine is started. A lot of life boat engines have hand cranks and decompression valves.

Possibly - but hardly ever - in fact every engine I have ever turned over, it turned over more easily when warm, mostly due to the changes of the viscosity of the oil. As for thermal expansion, this will depend more on the relative temperature difference of the cylinder and pistons as well as the materials used in both.

A minor pedantic point, no small engine will start (fire) while the decompression lever / valve is opened. It has to be closed before the engine will start.

[Dieseldude]

Originally Posted by Wotname

Possibly - but hardly ever - in fact every engine I have ever turned over, it turned over more easily when warm, mostly due to the changes of the viscosity of the oil. As for thermal expansion, this will depend more on the relative temperature difference of the cylinder and pistons as well as the materials used in both.

A minor pedantic point, no small engine will start (fire) while the decompression lever / valve is opened. It has to be closed before the engine will start.

True, warmer oil can counteract the effect of wider clearances in a cold engine. And engines with decompression valves often have a linkage that automatically closes the valve when the engine is rotated a revolution or so. This fact that some decompression valves self close can be overlooked. I've not hand cranked an engine for quite a long time. Thanks for the reminder. I have seen a large engine started with indicator cocks left open. Not a pretty sight to see fire and smoke ejected on each power stroke. It is quite messy and quite noisy.