91 BB w/ 5.9 cummins alternator might be bad?

[JHerrin]

Ok...so today my girl went to start the bus. Woomp...woomp it went. I checked the battery and got 11.2 volts. Hmm. hooked it to her car and it fired up after a few minutes. Putting the volt meter on the battery as it was running showed me that the voltage was dwindling quickly. Checked the back of the alt as it was running and it was doing the same. Bad alt is my best guess. I unhooked the battery pos as it was running and it died. Bad alt right? Any suggestions would be regarded as gold to me right now. THanks.

[Tango]

Is your engine an electronic model or mechanical? MY 3.9 is mechanical and only needs juice to start. Once going, it keeps going until the fuel is cut off.

[JHerrin]

It is mechanical. Strange that it drains the battery as it is running. Never had a problem like this and I am stumped.

[JHerrin]

I am hoping I am missing something as replacing the alt does not make me smile. Belt, placement...it seems like a pain. Its a Delco btw.

[Elliot Naess]

Originally Posted by Tango

Is your engine an electronic model or mechanical? MY 3.9 is mechanical and only needs juice to start. Once going, it keeps going until the fuel is cut off.

My 1992 had an electric solenoid turning the fuel on and off. Also, that solenoid is controlled thru an electronic two-stage relay. Once the engine is running, the relay reduces the voltage to the solenoid, to keep the solenoid from overheating. But it seems worth mentioning that this system is there. (I removed it and installed a manual cable for reliability.)

My alternator turned out to be a common automobile type. So might not be terribly expensive.

[AlleyCat67]

My Thomas only read 11.2 the other day but she turned right over..... once she was running I noticed the voltage reading was a little lower than I'm used to seeing..... where she'd been putting out 14.0 or 14.1 she was down to 13.6.... not terribly worried but a little concerned about the unexplained drop..... but it had been a little cooler the last few days than it was previously plus she sat for 11 days without being started so that might account for part of it too.

Not really sure why yours wouldn't start... unless maybe it had been sitting a while or was on the cold side.....

[cadillackid]

if you are going to run a lot of electricals on your 12 volt system.. id recommend the Bosch SB-200 (200 amp) alternator... it can be run as a 1 wire or connected as an SI type... it puts out 80% of its power at 1200 Alternator RPM (not to be mixed up with engine RPM)... its made in many different configurations and chances are your current pulley will just bolt right on it.

-Christopher

[JHerrin]

Replies appreciated! Ole Gary was started wit no problems bout 12 days ago. It has never not started. Battery is new but I did find that the neg cable to it had loosened but tightening did nada. If I do replace the alt, pointers to do that will be helpful. I am anxious to wake up tomorrow just so I can start working on it.

[JHerrin]

Bosch eh? I looked at that one online and was curious. I am still wondering about the one in the bus now. I thought alts were all or nothing as far as voltage? Baah....

[cadillackid]

they can be partial if the diode bridge is failing...
but when you measure the voltage at the big red wire on the back of the alternator that is a direct connection to your battery so you are seeing your battery voltage.. if you disconnected that wire from the alternator and measured at the alternator terminal you might then have 0 if the alternator has quit completely..

also to note is some alternators require a field-sense wire to "turn-on". if thats the case on yours and the fuse blew on the sense line then the alternator would fail to charge. .. or sometimes require the engine be revved up a few times to get the alternator to 'excite'.. so if you jumped the bus and just let it slow idle it very well may have never 'excited' so the voltage would drop till the solenoid closed and the bus would stall out..

-Christopher

[JHerrin]

Awesome advice Christopher. I am now trying to find out if my engine indeed needs to be excited so to speak. We did just idle it for the most part for the 10 minutes or so it ran. Ill pull the red wire in the morn first thing, run the motor on a jump and check just the post for voltage. If none...pull alt. If there is any at all does the solenoid then come into play? Can alts short if you cross the neg and pos on the back of the alt?

[JHerrin]

Well well. Pulled said alternator out after testing red wire stud that was bare. No voltage or very little. Found a shop close to me (Mt. Airy NC) that rebuilds them and have decided to spend my hard earned money at a local business. Parts and labor I am happy to spring for in my local community and the place has a stellar reputation. One other question....The wires and fittings/terminals that attach to the alt look like a childish attempt at forgery. They suck. I weld and build wooden boats but have little time with such big stranded wire. How are they crimped to ring connectors? Special tool or just souter them? Turkey day camping a few miles from the house is looking up!

[cadillackid]

usually they are crimped with a special crimper for the big wires.. there are different types.. I have one that you put the terminal and wire in and then whack it with a hammer.. it works on the really big stuff.. some people like to crimp it on and then fill it up with Solder.. I sometimes add solder if It seems like my connection isnt as good as what I want it to be..

if those wires were worn and someone crimped new terminals on them with regular Pliers it can easily look like a Hack Job!
-Christopher

[JHerrin]

Found out that a buddy of mine has one that is pneumatic. Go figure. Its for linemen work and big cable. Looks deadly and I may lose a finger but it will keep that ring terminal I do believe. Thanks again Christopher.

[Dapplecreek]

JHerrin - whereabouts are you? I live about a half-hour east of Hillsville, not too far from Mt. Airy. We are interested in building our own skoolie.

[Elliot Naess]

I'm fond of soldering, but there are sound arguments against it -- primarily cracking from vibration.
Recently I watched a utility lineman splice the 220 Volt cables going into my neighbor's house. He crimped the connectors with a hand-held battery-powered tool -- which does the job absolutely correctly every time. Good for another 50 years.
But no make-shift crimping, for sure.

[JHerrin]

I am in JOnesville and yeah....come on by. We are working on the bus all day today(Sunday 11/20). Painting and taping and what not. You can call me at336-483-5597. Name is Jeremy.