How to kill a starter

[JohnEd]

This relates to the previous thread about starters....but.  I have a friend that rebuilds all things alt/gen/starter for heavy equip/Monaco/Merithon/trucktrucks.  He knows whereof he speaks.  I had asked him some generic questions and he came up with something I had never heard.  A "low" battery will fry a starter.   He said that the current draw from a low battery will be less than a new bat at first but letting it crawl around will draw every amp the bat has and the starter will fry.  I reflected on how many times I read a Knut say he had low bats and after a couple minutes of cranking at low speed he gave up and charged the bats....WALA....fired on the first half turn.  From what Cris told me the Knut, in that case, narrowly dodged a bullet.  Now I really don't know what the R&R cost is for4 a 8V92 starter but I am almost positive it would be cheaper to charge the bats.  Isn't it 12.6 or 25.2 volts means full charge?  How low should the voltage have dropped to that you would not want to try a start for the starters sake? 

Just passing this along but I think knowing what the min voltage during cranking should be is a valuable piece of data.


John

[jjrbus]

To rebuild a 6V71 starter is $280 with tax!!

[Blacksheep]

All I can say is my bus must have a feature on it that won't allow you to fry the starter from low batteries because if they are the least bit low, I get nothing at the switch. I mean NADA! It won't allow me to crank sqautt! Charge the batteries and as you say WALA!
Since then my on-board battery tender has made sure my start problems never happen again!
Ace

[luvrbus]

At one time or the other I think all buses had the low voltage relay but over the years people have bypassed them I still have mine and it works if the batteries are not above 11.9 no start,and never had a starter problem in 18 years     


JohnEd I need to make a correction about the voltage mine 10.9 volts not 11.9    sorry

[JohnEd]

Luvr,

"And another country heard from".  I have never heard of a low voltage relay.    Sheltered life, I guess. You mean the mfr thought "low V" so detrimental that they installed a relay that keeps you from applying it to the starter?  I guess that makes the case.  Thank you for sharing that.  Save a starter and reconnect your "low V cutout relay".  Sound advice!  I bet that would send people straight to "fix the battery, Stupid" and spare them the fruitless and needless adventure of crawling through the bowls of the engine bay/battery compartments.  How many "Old Timers" had analog voltmeters that would clearly show a voltage drop of .7 volts or eyes that would see it if the meter could show it?

One of the things that scares me about this topic is the way Knuts are going about determining how well the starting sys is working and troubleshooting.  I "always" connect the voltmeter "across" the starter and make my connections to the stud and starter frame.  That is the only place you can measure with confidence for the true V being "felt" by the starter.  I have even found instances where the full voltage was present at the connector to the starter but not at the "stud".  In one case it was due to a thin oxide on the washers, laid down for years, on the stud and another was caused by a fiber washer that some underachiever had installed under the washer and nut.  Neither smoked cause they had been heated up so many times they were clean.  If you have low cranking voltage at the battery you can't have better at the starter but having V at the bat doesn't mean the starter is actually seeing that full voltage.  From Luvr's info if you drop to 11.9 at the bat it won't try.  Now, what does 11.9 break to at the starter while cranking?  I'll ask Chris on Monday for sure but I think he said 9 volts, in 12 volt system, was "death to Smoochie".

Thanks again Lvr,

John

[bobofthenorth]

I have a very simple rule about starting born out of buying several starters: if it doesn't start on the first roll then I go looking for the cause.  The cause can only be one of two things on a diesel - cold or fuel.  If its cold then it needs to be warmed up or fed ether.  If its fuel then you need to fix the fuel system - there's a leak or a bad check valve or an empty tank. 

Diesels are about as simple an engine as you could ask for.  There's very little to go wrong and a properly functioning diesel should light right up.  I realize this advice doesn't apply to some of the new electronics that have to roll over several times to build up oil pressure but most of us are dealing with the antiques and they should light up right away.

It takes a lot of amps to roll these things over for extended periods of time and that is what eats starters.  Higher volts means less amps so dying batteries make things worse as do bad cables, bad connections, bad relays, etc.

[Len Silva]

They can be killed but are still extremely rugged.  Some years ago, my 4104 quit running. Turned out to be a cracked fuel line.  At any rate, I was in a very bad spot and moved the bus about 15 feet just on the starter.  I figured I was sacrificing the starter but it was necessary.  Ten years later it was still working fine.

Len

[gus]

John,

The thing that kills the starter with a low battery is the extra high current.

The slow turning starter also is usually used longer than normal and this adds to the heating.

[fe2_o3]

    In a past life I worked over the road repairing heavy equipment. Some were electric forklifts.
   I found the biggest killer of electric motors to be low voltage.  The motor needs energy, so the lower the volts, the higher the amps it draws.
   Low volts + high amps = arc welder. The solenoid or motors inside becomes an arc welder. The life of a starter can end in just minutes.
   If the battery voltage is maintained, the starter gets a better chance at life...Cable