12valve Cummins no start

RenegadeT

RenegadeT

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My 12v Cummins isnt starting, need some help on diagnosing what's up. It sounds electrical, but both my batteries are measuring above 12volts (disconnected with the handheld voltmeter). I crank it and it sounds like a dead battery...seems OK for half a second, then the dash voltmeter drops to 8V and cranking quickly stops. Its like thats all the juice its got, cuz another attempt doenst give anymore starter RPMs. No clicking (like I'm used to in my Jeep :lol:), just lack of "oomph". Batteries are still at 12.2V.
I'm off to DTR to read more about the starter, I now there's a common failure and updgrade with brushes or soemthing. I'd like to know an tips or what else I can check before I start pulling the starter. Is the starter like any gas engine starter, where I could bring it to a parts store for bench check?
thanks
 
are yoiu reading 12.2 PER battery while cranking?

12v while not under load doesnt mean anything....hell most dead batteries will read real close to 12v
 
12.2 PER battery just sitting there, not cranking. Everytime I have a dead battery, they are less than 12v, maybe 10 or 11, but I think 12.2 is exactly where its supposed to be. I might bring them in to get load tested, its easy.

I think I'll try using my HD jumper cables and connect each battery directly to the starter, see if my cables are bad. This truck spent most of its life in Boston, corrosion is its middle name. About 6 months ago, I soldered on new lugs to the factory cables. I am now getting wicked corrosion on the drivers side positive terminal, the one where the alternator and power distribution center connects.
 
braxton357 said:
Sounds like your grid heater is cycling and killing the batts.
Click to expand...

cycling in the key-off position? I would have expected less than 12v. I've only tried to start it twice, but both times I let the wait to start light go off, I can see the dash voltmeter bump back up. Dunno, maybe I'll disco the heater and see if I get my oomph back. Kind of makes sense though, I get a brief half-second of what sounds like decent cranking, then maybe the grid heater kicks back on somehow and sucks the amps.
 
RenegadeT said:
cycling in the key-off position? I would have expected less than 12v. I've only tried to start it twice, but both times I let the wait to start light go off, I can see the dash voltmeter bump back up. Dunno, maybe I'll disco the heater and see if I get my oomph back. Kind of makes sense though, I get a brief half-second of what sounds like decent cranking, then maybe the grid heater kicks back on somehow and sucks the amps.
Click to expand...


sounds like a bad cable or bad ground, enough to light everything up, but no go under load, do a visual on cables loosen all the connections, move them or better yet clean them then try aain, starter contacts are bad about going out too. Also, make sure one of your batteries doesnt have a dead cell draggin the other down with it, I'm betin is a shitty connection somewhere, good luck
 
hmm....
http://www.autoshop101.com/trainmodules/batservice/113.html
OPEN CIRCUIT VOLTAGE
A digital voltmeter must be used to check the battery's open-circuit voltage. Analog meters are not accurate and cannot be used.
1. Turn on the headlamps' high beam for several minutes to remove any surface charge.
2. Turn headlamps off, and connect the digital voltmeter across the battery terminals.
3. Read the voltmeter. A fully charged battery will have an open-circuit voltage of 12.6 volts. On the other hand, a totally dead battery will have an open-circuit voltage of less than 12.0 volts.
Note: If the battery is 12.4v or higher, proceed to heavy load test. If the battery is less than 12.4v, the battery must be fully recharged before testing. Be sure to remove the surface charge completely; this is the number one mistake technicians make. If need be, place a load tester on the battery and load the battery for 10 seconds at approximately 200 amps. Allow a few minutes for the battery to recover then measure the open circuit voltage. This should remove the surface charge and allow an accurate open circuit voltage measurement. (Remember: a reading of 12.4 volts or higher load test the battery, 12.3 volts or less, recharge the battery.)

% of charge
12.6v = 100%
12.4v = 75%
12.2v = 50%
12.0v = 25%
11.9v = 0%
Click to expand...
 
1983Bronco said:
sounds like a bad cable or bad ground, enough to light everything up, but no go under load, do a visual on cables loosen all the connections, move them or better yet clean them then try aain, starter contacts are bad about going out too. Also, make sure one of your batteries doesnt have a dead cell draggin the other down with it, I'm betin is a shitty connection somewhere, good luck
Click to expand...


This too is the number one reason people call me to come look at their "bad starter" or battery, bad cables or corroded terminals. The twin batterys make that less likely though.

Have you tried jumping it from another vehicle?
 
check your negative cable to the block.. I had the same issue.. the cables was corroded, once i cleaned it all was good
 
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