Ford Lehman 120 not starting…sometimes

[apagano]

Ford Lehman 120, Port engine when underway sometimes will not start after a night at anchor, slow turn and then nothing, simular to something like a dead battery issue and will then start when I run portable generator for 15 minutes or so.. At dock I checked battery wit a tester and got a good battery reading. At dock engine starts always when on shore power. If my starter battery is dead, or on the way out, why would I get a good result from a test?
Thanks in advance

 

[Comodave]

Check the voltage at the starter when it is cranking. If it is low it could be a bad connection or corroded connection.

 

[SteveK]

Ford Lehman 120, Port engine when underway sometimes will not start after a night at anchor, slow turn and then nothing, simular to something like a dead battery issue and will then start when I run portable generator for 15 minutes or so.. At dock I checked battery wit a tester and got a good battery reading. At dock engine starts always when on shore power. If my starter battery is dead, or on the way out, why would I get a good result from a test?
Thanks in advance

what do you consider a good reading at the dock?
As said the voltage taken while cranking at the starter will tell a different story. Starts with a portable generator suggest a higher voltage getting to the starter thus it starts. Clean connections and if that does not work get a new battery.

 

[jleonard]

Learn how to do a proper voltage drop test at the battery and starter.
Youtube has many videos that will teach you how.

That said, I have been fooled more than once by using a battery tester to check a battery that is starting a diesel. I don't trust them any more.
If in doubt I simply replace the battery.

 

[C lectric]

A static test of the battery voltage is useless.
Almost all meters, analogue and digital, can get enough current from an almost dead battery to give a "GOOD" reading or well over 12v. But the battery will fail to deliver the FAR HEAVIER current the started needs.

A proper test will be attach the meter leads to the battery post and then try cranking.

If the battery voltage drops below about 10.5 v then the battery is suspect. Keep in mind though that 10.5 is a minimum , higher would be BETTER.
If the battery fails this then it likely needs to be replaced.

If the battery still shows above 10.5 then attach the meter leads to the starter motor terminal, the big heavy + one and to a good ground, usually the - terminal. Some batteries ground through the case to the engine block.


If the voltage drops more than another volt below the battery voltage then the cables and connections are part of the trouble. ie. less than 9.5 v

ALL connections must be clean and tight. NOt just looked at, the clamps need to be removed and cleaned. THere are inexpensive terminal cleaning brushes that do a good job. Auto parts stores. Usually it only takes minimal effort to adequately clean them.


If the bolt ears of the clamp touch as you do up the bolts then the clamps need to be replaced. If those ears touch then even though the bolt is tight the contact between the terminal and the post may not be.

Personally, I would ensure all the connections at the battery AND the starter are gone through , cleaned and tightened and any replacements/repairs done first. Many starting problems are simply poorly done connections.

I also recommend strongly that all the connection be smeared with No A Lox
[a conductive electrical contact paste] or in many cases a silicone grease, often called a dielectric. Again an auto parts place of small industrial supply.

Only a good smear is needed, not gobs and the connections will stay oxidation free for a LONG time.

 

[Marco Flamingo]

When I put in the electrical service to my house, the electrician for the State (who needed to sign off on the installation) said that NoALox was only for aluminum to aluminum contacts. Not sure if it does any harm for copper or tin or just doesn't do anything for copper and tin.

 

[Lepke]

If the engines have separate starting batteries, swap them, and then try to start.

 

[catalinajack]

When I put in the electrical service to my house, the electrician for the State (who needed to sign off on the installation) said that NoALox was only for aluminum to aluminum contacts. Not sure if it does any harm for copper or tin or just doesn't do anything for copper and tin.

KoprKote will do the job.