dumb ? from CA where 40 degrees is freezing - PeachParts Mercedes-Benz Forum

#1 03-27-2004, 10:46 PM

I want to jump my 1980 300sd so the starter gets 24 volts. Is it as simple as connecting the jumper cars positive to the jumped cars neg and neg to positive. Can I do this with a new car as the jump vehicle or will it hurt the electronics. Could someone please inform this diesel driver that never waits for glow plug light I just turn key and go. The proper way to get 24 VDC to thee starter is?
Thanks Dave

dieseldiehard · #2 03-27-2004, 10:55 PM

OK I give up, what's with the San Jose weather that its so cold you have problems starting a diesel? This isn't April 1st yet, no fooling?
Whatever you are trying to do, forget putting 24 Volts on the car in any way. If the starter ONLY received 24 V, granted it would crank your car like there was no tomorrow. Put 24 V on the rest of the car and you will fry the lights (in the dash as well as the body) and the modules that receive that voltage will also go South for the winter, never to return.

DDH

#3 03-27-2004, 11:12 PM

I thought I read somewhere that this was a common practice back east where it’s real cold. The reason I want to do this is this motor is a real ##### to get primed and it has been out of the car for 6 months completely stripped down. I thought if I could crank it real fast I would save some time having to recharge batteries between tries. The lights blower motors are usually specked to 36 volts so they are using off the shelf parts 24vdc is real common in industry and military no doubt same as lights ect in a non computer controlled car. maybe thats why I cant find much about it using search.
TKS Dave

190D22 · #4 03-27-2004, 11:21 PM

Connecting the batteries as you described will short out the batteries to eachother which will heat the batteries up and will eventually make them explode. This is a sure way to destroy your batteries. To do 24V to the car you'd have to disconnect the negative from your car connect the batteries as your described EXCEPT put the car's negative to the 2nd battery's negative post (this is the 2 batteries in series). But again I wouldn't recommend this, I would expect the electrical systems in the car to all fry.

If you want to get the battery flying like you said... why not run 24V into it when it's OUT of the car?

#5 03-27-2004, 11:59 PM

I have a home made engine stand I never considered it might one day hold let alone run a diesel engine. I did not think it safe to even try to start it on the stand. And that was a real unfortunate oversight on my part. It would have been great to run it on a stand.

mplafleur · #6 03-28-2004, 12:11 AM

Excuse me, but you'd have to disconnect the cars battery negative and connect the negative terminal to the jumper battery positive. Then the jumper battery negative to the cars ground cable. This would give two batteries in series.

Wouldn't recommend it though.

HGV · #7 03-28-2004, 12:48 AM

If I read the post correctly, you have the following situation;

Car engine has been taken apart and is no bask together to be started and it is out of the car.

i would first put the engine back in the car. Not sure why you would want to prime it out of the car.

Prime the engine by removing the injectors and crank the engine with no compression. It will spin like crazy. Keep doing this until you have oil pressure and the injector tubes are spurting fuel out. i usually place a towel under the injector tubes so you don't make a mess. This should not take more than a minute.

then put the injectors back in and glow for twenty seconds and crank. I have used this technique and have never drained a battery on a properly assembled engine.

henry

#8 03-28-2004, 01:50 AM

I just put the engine in the car. Thank you for the information. That is how I am going to do it great idea.
Thank you
DHS

#9 03-28-2004, 09:59 AM

Hi Dave.

Read this link:
Engine rebuild - fuel prime DIY

Louis.