Won't start...

[deuce200385]

I have a 1985 M1008 (just bought it) that won't start without a jump....I have about 11.5v while running and same when not but my batteries look brand new, they previous owner told me that it is converted to 12v with a 6.5's gear reduction starter.... my question is before i just replace batteries should i look at the alternator also? and if so where is best to buy an alternator and since the the truck only has one now, what one should i be looking for? sorry for the dumb questions but this is my first 1008 and diesel.










1985 M1008
6'' lift on 37'' humvee tires
6.2l with 6.5 turbo
17,000 miles

 

[FMJ]

I think your alternator or charging circuit is not working, start the truck, then pull the negative battery cable off, if it dies, the charging circuit is not working.

You should have more than 11.5 volts when the motor is running.

 

[Warthog]

Since your truck has been converted to 12v (we have no idea how it was done and if the wiring was hacked up) any 12v alternator that will fit should work.

You must have your batteries fully charged and load tested before you can make any determination if they are bad or not. You can not just look at them and say "hey they are great!"

Most diesels need fully charged batteies to get the engine to spin fast enough to over come the high compression.


Not picking on you Deuce200385, but for others that are considering converting tho 12v, this post is what will happen when you sell the truck. The new owner comes here with an issue and we have no idea how the conversion was done. Please include a wiring diagram to the new owner.

 

[FMJ]

Here is a link to a 12 volt conversion that actually works, look at it and see if your truck was done the same way, otherwise, you may have a big mess on your hands.

http://www.roscommonequipmentcenter.com/news_notes/nn10.pdf

 

[southdave]

Do what fmj says.. but it sounds like you have a ground issue.. I am assumming the guy left the driver side alt inplace. there agruond to block there and there is one on the oppsite endof block to the neg bus bar.
check those and go though all the wire and RR.

 

[Matt65]

Welcome Deuce. You've come to the right place. Good information already given. I would say start simple. Charge both the batteries slowly overnight, then have them load tested.

Be careful charging and jumping the truck off, sparks and blue smoke are no fun. If your unsure or don't feel comfortable working with the modified electrical system I'd say stop. Post a few pictures from under your hood start at both batteries, along the firewall, and to the alternators. This will allow us to see what your working with. Also, I have seen a couple of factory civilian 12 volt M1008 clones slithering around so I would confirm the VIN as CUCV. http://www.steelsoldiers.com/showthread.php?13193-Decoding-CUCV-Vin-numbers

I have a link to the TMs in my signature, but use with caution since your truck has been converted.

 

[MarcusOReallyus]

I agree with most of the above. It's way to soon to start guessing at root causes. Until you know what you have, it's impossible to troubleshoot anything. Slow overnight charging, with both batteries disconnected, get them tested, and give us lots of pictures.

And like Warthog said, the batteries can look shiny brand new and still be junk. Don't go by appearance, have them tested.