Starter system fire

Hey guys, I'm a somewhat new member, and also new to the cucv's. I bought a 1984 m1009 getting close to about a year ago, and have had it running on and off since then. My current problem is that when I go to start it; it will turn over then die. After repeating that process a couple times I noticed that some of the wiring going to the firewall was burning. Does anyone have any suggestions as to where I could begin to fix the problem? Anything would help thanks!

It's likely you've fried the fused link. Check all your cabling and clean all the terminals. Replace the burnt links. Also research the "doghead relay".

Low voltage will do that everytime. When the voltage drops it makes heat and the relay is the weak link in the starting system. It welds the contacts fast in the relay and and the fireworks begin because the voltage keeps dropping as it keeps cranking making more heat. Check your batteries for the proper voltage and avoid cranking them down and you should be good. I never done the relay change. I just keep the batteries charged fully.

First of all, make sure your batteries are fully charged, and have them load tested. Failing batteries can lead to excessive loads and heat in the wiring.

Second, check all your battery cables for good connections, etc. Corrosion can occur in the cables, near the connectors, and lead to increased resistance, etc.

Start your reading here:

http://www.steelsoldiers.com/showthread.php?122571-Fusible-Links-101

http://www.steelsoldiers.com/showthread.php?103110-Burned-Fusible-Links-after-Starter-Run-on-Explained-and-Illustrated

http://www.steelsoldiers.com/showthread.php?60960-doghead-starter-relay-modifcation

http://www.steelsoldiers.com/showthread.php?136886-Alternator-and-starter-parts-amp-repair-kits

Okay, I will definitely check all my wiring, and connections etc. thanks for all the help!

Also it's good to remember that batteries store energy in a chemical process. If you do a huge power draw like spinning a 3kW-5kW starter motor after running 3.2kW of Glow Plugs their ballast resistor, it takes a while for the battery's chemical process to recover. Think of it like filling a jug of water through a straw. For larger commercial generators, the auto start system features a timer that ensures the crank only lasts 10 seconds, then there is a 30 second break for the batteries to recover and the starter and wiring to cool off. After about 3 tries it stops trying to save the batteries and starter.

Note that power (Watts) is derived from Volts times Amps: 25.6V * 117A = ~3000Watts (3kW). If your batteries are not recovered from a pulse load (like the last time you tried to crank), it'll still take about the same amount of power to get the engine rotating, but if the battery is down at 22V when you try again: 3000W / 22V = ~136A, or a 16% increase in current draw. Another thing is the rotational speed of the DC motor is directly related to the voltage applied to it - so as your battery voltage drops with too frequent retries, you're actually spinning the engine slower each time so it won't start as easily.

They don't teach you this stuff when you learn to drive a car, and your mechanic probably won't spent a lot of time helping you not come back to them... In general, patience is a virtue.

cucvrus said:

Low voltage will do that everytime. When the voltage drops it makes heat and the relay is the weak link in the starting system. It welds the contacts fast in the relay and and the fireworks begin because the voltage keeps dropping as it keeps cranking making more heat. Check your batteries for the proper voltage and avoid cranking them down and you should be good. I never done the relay change. I just keep the batteries charged fully.

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I still firmly believe that the above statement I made 2 years ago is accurate and valid. And by keeping batteries charged fully. I mean when they get bad I change them both. I just looked and my Crown of Thorns M1009 still has January 2010 batteries in it and starts fine all stock.This one. I use it very hard. But it only gets about 1200 miles a year from each annual safety inspection.