I am confused - PeachParts Mercedes-Benz Forum

MVK · #1 08-13-2002, 09:42 PM

Hello folks:
Last night my nephews 1991 oldsmobile van V6 3.1 lit needed a jump as the battery had lost its power. It was not used for a few weeks and I think the blinking alarm light used up all the juice. Now comes the real Question.
I tried jumping his van using my 300D turbo, and it hardly rotated his engine by few rpm. I waited for 2-3 minutes and tried again and no luck. I reved the benz to 1500 rpm and then tried to jump start the van and again no luck- just 3-4 turns on the olds engine then dead again. Finally I gave up using Benz as the source car. Got out my wifes 1988 honda accord and tried, no luck at Honda's Idle. Reved up Honda to 1500 RPM and waited 30 seconds and Bingo the olds started with authority.

I am hurt now. Why cant my MB do what her little accord did? This has happened before too and I have never been able to use my MB as a source car in a jump situation. All jump connections were fine still no go WHY?? WHY??

So today checked the battery, its 12V, Alternator giving juice at 13.7-14 volts and stayed at same when lights were turned on or when rpm were increased. So my alternator passed the test with flying colors.

What could be the problem? Mind you my car runs fine, no starting problem, no other electrical problem.
Someone please help so I can sleep good.

MVK

JohnM · #2 08-13-2002, 10:15 PM

I think you just weren’t getting a good connection on the battery or ground. I had a similar problem once and I later discovered that some of the jumper cable wire strands were broken where it connects to the clamp and only if I happened to place the cables in such a way that the bend in the cable made the broken strands in the cable connect did it work. The bottom line was that the cables didn’t have enough amperage capacity and had too much subsequent voltage drop while with the broken conductors to start the other car. And of course, that meant the wire was heating up at that point and making matters worse. I tossed them as soon as I saw it and got a better set with a heavier gauge wire.

Your problem may have just been the clamps weren’t strong enough to get a good bite onto the battery and ground (on either end), which could mean not enough amps were delivered to turn over the olds. I always try to buy a quality set with lots of strength in the clamp springs so they bite down good. Remember, there are a LOT of amps involved at 12V to start a car.

Future cars are rumored to be possibly going to a higher battery voltage, in the neighborhood of 50V, until that happens, you need big wire with good electrical contact at all four connection points.

JohnM 1983 240D 4sp 154K

MVK · #3 08-14-2002, 07:53 AM

Thanks for info but my cables are excellent. Its the same cable I used for giving jump from Honmda. But I will check again.
MVK

Gilly · #4 08-14-2002, 09:26 AM

I would also assume a bad set of jumper cables, it's the only thing that makes any sense assuming you were going off both battery terminals on the MB. If you connected the black cable to the engine, not the ground terminal on the MB, then possibly the ground strap from the engine to the chassis is loose, corroded, or missing, it connects to one of the bell housing bolts, you almost have to be under the car to see it. This could also be true on the Honda I suppose, if you connected the black cable to the Honda's engine.
But it is possible to have a bad connection from the cable to the clamp on the jumper cable, the problem may be intermittent and when the Honda started you just happened to have a good connection between the cable and clamp. I'd look over the connections really well and then if nothing is found I'd still check it with an ohmmeter, but be sure to twist the cable around a little to see if you see the value fluctuate.

Gilly

190D22 · #5 08-14-2002, 09:52 AM

Well these cars do have pretty puny alternators... I will never jump anyone from my cars (except myself of course) because I am afraid of cooking the voltage regulator or alternator of the good car. I will jump the benz from the jeep, but I won't attempt the other way around. It wouldn't surprise me if the honda has a bigger alternator in it. Mine in my 190 is only 55A. My brother's '90 4cyl ranger has an 80A.

And the new voltage for cars is goin to be 42 volts. I don't know why they didn't go to 48V...

MVK · #6 08-14-2002, 06:07 PM

Thanks guys.
MVK

Elripster · #7 08-14-2002, 06:14 PM

Quote:

Originally posted by 190D22
Well these cars do have pretty puny alternators... I will never jump anyone from my cars (except myself of course) because I am afraid of cooking the voltage regulator or alternator of the good car. I will jump the benz from the jeep, but I won't attempt the other way around. It wouldn't surprise me if the honda has a bigger alternator in it. Mine in my 190 is only 55A. My brother's '90 4cyl ranger has an 80A.

And the new voltage for cars is goin to be 42 volts. I don't know why they didn't go to 48V...

One possible reason the Ranger has more amps is that it requires much more electricity to run. Figure the diesel once it's going, you only have accesories to operate. The gas powered cars have spark plugs, engine computers, sensors, fuel pumps, electrical injection stuff, sometimes electric fans, plus all the accesories as well. That would likely make for more drain and require more amps.

Frank

MVK · #8 08-14-2002, 11:37 PM

Thanks Bill. I think I am going to check my jump cables and also get my alternator checked for the amp output.

MVK

P.E.Haiges · #9 08-15-2002, 12:54 PM

You might have a weak battery. Enough to start your engine if it starts easily but not enough to make up for the loss in the cables.

P E H

diesel don · #10 08-15-2002, 01:16 PM

MVK:

I have jumped our Detroit Diesels (in our coach busses) with my 300D when the 15 passenger vans wouldn't turn the big 6V92's fast enough.

Don

#11 08-15-2002, 04:10 PM

And the new voltage for cars is goin to be 42 volts. I don't know why they didn't go to 48V... [/B][/QUOTE]

Well the answer is that todays alternators and battries put out 14 volts so in parrallel the same alternator with higher amps can charge the three battaries that will be supplying in series.

My 300d once was deader (is that a word) than a door nail, ofcourse after checking everyfuse and connection I decide to check the battery which turned out ok to except the post and terminal were corroded at the contact just removed and cleaned, everything fine after that.
Fareed

P.E.Haiges · #12 08-15-2002, 06:54 PM

Fareed,

Yes 14 X 3 = 42 but it is impossible to have batteries connected in series and parallel at the same time.

The reason they are going to 42 volts is solid state devices can run on that voltage and they can reduce the size of the wires to save money. However, I don't know how much more a 42 volt battery will cost.

It is also possible so that some of the electrical and electronic parts will be compatible with the hybrid cars (gasoline/diesel electric or fuel cells)

Seems to me that the 42 vollt batteries will be less reliable because with a 12 volt battery you have a 6 to 1 chance of a cell going bad and with a 42 volt battery you have a 20 to 1 chance. Thus the 42 volt batteries should only be one third as reliable as 12 volt ones.

P E H

Gilly · #13 08-15-2002, 11:00 PM

PEH:
You DO have the option of editting your own posts, there is a button on the lower right corner of each post that says "edit", just click that and you will have a screen with your post on it on which you can make corrections and resubmit the post, it will still appear in the proper order.

Gilly

P.E.Haiges · #14 08-15-2002, 11:19 PM

Thanks Gilly, I didn't know that (EDIT).

P E H

PS, If you see this I tried it and it works. What does the quote button do?

Gilly · #15 08-15-2002, 11:52 PM

PEH

Sorry, never have used that one. I see people putting in quotes all the time, seems like a waste to me, but that must have something to do with using quotes of earlier posts.

You can also go back to that one "I'm sorry" post, hit the edit button and there is an option to delete that one post. So you can go back, edit the one post to correct who you are addressing it to, then delete the "sorry" post.

Gilly