Hard to believe both alternators would go out at the same time. Seems you would of got a code or something if just one went out.

 

I will just throw this out....reverse polarity on the batteries will sometimes take out the diodes on the alternator ...that is an electrical check valve.
and will drain the batteries...so I hope you take your alternators to a reliable shop that can check them...they are called "bridge rectifiers".
if they are bad..it is fairly cheap to have those replaced...
I have been down that road...
good luck....I always get very nervous "jumping" friends off..sometimes it is cheaper to go buy them a battery..especially with cars and trucks with computers...that can get very expensive...

 

If you know what you're doing, and do it correctly, there's virtually no chance of harming your truck when "jumping" another vehicle.

The biggest mistake most make is to let their own truck run while the other attempts to start. It must be OFF.

The second mistake is letting another person be involved in the process at all!

No ifs, ands, or buts!

Pop

 

putting the cables on backwards (reverse polarity) is the problem...and one touch of the cables backwards usually does the damage..

You just take the chance everytime you jump someone off...plus you never know what is going on with the problem car...the question is .....

are you lucky?

 

Did you have them rebuilt?

 

I never knew this. Why's that Pop?

Another mistake people make is when hooking the NEG jumper cable to the dead vehicle. They always hook it to the NEG battery post instead of a good ground on the engine or chassis.

 

Never had any problem doing this. Just disconnect as soon as the other car starts any time you jump start.

 

"The biggest mistake most make is to let their own truck run while the other attempts to start. It must be OFF."

That's exactly right. I was taught that the diodes in an automotive alternator running a full-wave bridge rectifier circuit are more subject to failure when that rectifier circuit is fully energized and the current is being subject to extreme fluctuations due to the unstable environment that occurs when jumping another vehicle.

 

Interesting, I never knew that about shutting off the vehicle when jumping. So if it is running is it an even bigger issue to rev up the engine to try and get more "juice?" We did not get them rebuilt, two brand new ones .... On the bright side I have two brand new ones that should be good for a long time now that I know more about jumping and not letting anyone else handle the cables ....

Did anyone have anymore input on the mystery tube I mentioned? See if I can get a pick later. It would seem really dumb to me if it was a fuel drain since its right in-front of the passenger exhaust manifold ....

Thanks for all the help and information everyone!

 

Open the fuel drain on the back of the fuel bowl (its the yellow plastic lever) and see if fuel comes out the other end, if it does then you know. Takes 2 seconds to do.

 

Because a starter motor presents a VERY-low impedance (or resistance) to the available current supply, and a lot of current is demanded (and flows).

That's something your charged batteries should supply just fine, but if your alternator tries to provide it too, a tremendous amount of current is passed through the diode pack. That's because the alternator is outputting about 14.4 volts, and the batteries are only supplying about 12.6 volts. If the diodes aren't rated for that high current (almost all are not) then you may "pop" one or more of them.

Some go open, some go short.

An open diode will not allow the alternator to provide enough current and voltage to maintain the charge in your own batteries, and they will start to go flat.

A shorted diode acts as a path to ground for your batteries through a stator winding, because if working correctly, they prevent that "reverse" current flow. It will get the alternator hot to the touch, even after hours of being off, and will drain the batteries flat virtually overnight. The current might get the battery feed wire in the harness hot enough to melt the insulation and can even cause a fire.

Either way, a bad diode is not a good thing. Every alternator has at least six of them (depending on design) acting as a three-phase, full-wave rectifier, and all of them must pass current in only ONE direction!

Or, youze gots a problem!

Pop

 

Have you ever calculated impedience? It's like the sum of all opposition in a circuit including resistance and reactance squared pied and fried, blah blah blah. Glad those years are over.

Nice accurate response.

 

Learn something new everyday on here. Thanks Pop

 

Me too!

Pop