Using a 12 volt battery to start a 6 volt engine

[Mark's 37]

Having trouble getting the rebuilt motor to spin fast enough to start. Spins well without the plugs but barely turns over with the plugs installed. I have oil pressure, fuel and spark. What is the proper way to try starting this motor jumping from my 12 volt Ford? Thanks.

[petehoovie]

Connect the jumper cables - positive side to engine block and negative to the lug on the starter motor...

[V8COOPMAN]

12v POS cable clamped onto the BIG lug on the starter.....right over the big wire is fine!

Now, when you're ready to spin (and start) the engine, turn-on your normal 6v ignition switch. WHEN you jam the NEG 12v cable against a clean, heavy GROUND on the engine (like a bolt, or BARE spot on block) the starter will crank! As long as the 12v POS stays on that starter lug ONLY, there is no chance that anything ELSE that's 6v will be affected. DD

[petehoovie]

Originally Posted by V8COOPMAN

12v POS cable clamped onto the BIG lug on the starter.....right over the big wire is fine!

Now, when you're ready to spin (and start) the engine, turn-on your normal 6v ignition switch. WHEN you jam the NEG 12v cable against a clean, heavy GROUND on the engine (like a bolt, or BARE spot on block) the starter will crank! As long as the 12v POS stays on that starter lug ONLY, there is no chance that anything ELSE that's 6v will be affected. DD

He didn't mention if he is still 'positive' ground....

[Mark's 37]

Still Positive ground. Using the Optima 12 volt Red Top from the 57 Bird. Jumper cable Pos to the block and the other Neg cable clamp to a long heavy pry bar that I hit the lug on the starter. The bendix hits but won't crank a full revolution and starts to arc weld the end of the pry bar. I have a battery charger with a 6 volt setting and a 60 Amp Start position. The engine turns better with this but still too slow.

[petehoovie]

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Originally Posted by Mark's 37

Still Positive ground. Using the Optima 12 volt Red Top from the 57 Bird. Jumper cable Pos to the block and the other Neg cable clamp to a long heavy pry bar that I hit the lug on the starter. The bendix hits but won't crank a full revolution and starts to arc weld the end of the pry bar. I have a battery charger with a 6 volt setting and a 60 Amp Start position. The engine turns better with this but still too slow.

That's got to be one tight engine. Were it me, I'd pull the plugs again and apply the 6 volts from battery charger @ 60 Amps to message it a little....

Do you have strong spark?

[V8COOPMAN]

Originally Posted by petehoovie

He didn't mention if he is still 'positive' ground....

Guys.......It makes no difference whether the car is wired POS or NEG ground. The way you're hooking-up has ABSOLUTELY no effect on any part of the entire 6v system. Essentially what we're doing is nothing more than runnung the starter motor on the workbench. PLUS, we know that those starter motors run the SAME direction whether POS or NEG ground. The only reason I suggested the polarity I did was to maybe keep it simpler to keep-in-mind which was HOT and GROUND from the 12v set-up. ALWAYS hook-up GROUND LAST! Disconnect GROUND FIRST! DD

[Mark's 37]

Originally Posted by petehoovie

That's got to be one tight engine. Were it me, I'd pull the plugs again and apply the 6 volts from battery charger @ 60 Amps to message it a little....

Do you have strong spark?

Yep...going to spin it more with the plugs out. Have a nice blue spark grounding the plug wires to the head. Picked up a new set of plugs just now. Don't understand how the 6 volt battery with the 60 Amp start feature spins it better that the 12 volt jumper battery with the plugs in or out. Anyway, used up my time and most of my patience for today. Hit it again tomorrow and leaving the 6 volt battery on trickle charge overnight. Thanks.

[petehoovie]

Originally Posted by Mark's 37

Yep...going to spin it more with the plugs out. Have a nice blue spark grounding the plug wires to the head. Picked up a new set of plugs just now. Don't understand how the 6 volt battery with the 60 Amp start feature spins it better that the 12 volt jumper battery with the plugs in or out. Anyway, used up my time and most of my patience for today. Hit it again tomorrow and leaving the 6 volt battery on trickle charge overnight. Thanks.

I can't wait! I'm really looking forward to that engine of yours firing up given how you've kept us informed of your progress from start to finish....

[Talkwrench]

Are we going to get a vid of the start up ; )

[RalphG]

Yes, I used that method to start my 52 Merc several times. I hooked up to the solenoid (starter side) with the booster cable from the 12 volt battery. As stated it makes no difference if pos or neg ground. This method isolates the rest of the old six volt system from the 12 volt battery and it goes only to the starter. Made a world of difference to starting for me. I made my final connection right at the external 12 volt battery rather than on the engine block. A little sparky but at least it wasn't under the hood.
See it in detail here.........
https://www.youtube.com/watch?v=wO25Y2zgShE

[Mark's 37]

Originally Posted by Talkwrench

Are we going to get a vid of the start up ; )

I prefer the option to lick my wounds in solitude if needed.

[Karl Wolf]

I've hooked up jumper cables battery to battery for years, dead 6v jumped by hot 12v.
ONE caution, though- hook up the 12v ground last, and disconnect it first.

Hydrogen gas will explode, and while it's never happened to me while jumping 12-6v, it makes an impressive mess, and loud noise. Really scatters the battery case, too.

Karl

[RalphG]

Originally Posted by Karl Wolf

I've hooked up jumper cables battery to battery for years, dead 6v jumped by hot 12v.
ONE caution, though- hook up the 12v ground last, and disconnect it first.

Hydrogen gas will explode, and while it's never happened to me while jumping 12-6v, it makes an impressive mess, and loud noise. Really scatters the battery case, too.

Karl

I've seen it done, (12 volt boosting 6) but I keep my distance and won't try it myself. Sulfuric acid in the eyes from a battery explosion is not something I want to risk.

[CSArno]

Want to mention, because I don't see it here. Are you using the right size battery cables for your 6v battery? Battery to solenoid, solenoid to starter and battery to ground? 12v cables are not big enough. Starter on 6v draws twice as much current as 12v therefore it needs bigger cables.

Was numbing it and doing some welding once in the vicinity of a battery charging with the caps off... BIG BOOM!! Thankfully the welding helmet protected my face.

[Randy in ca]

Originally Posted by RalphG

............I made my final connection right at the external 12 volt battery rather than on the engine block. A little sparky but at least it wasn't under the hood.

Originally Posted by RalphG

I've seen it done, (12 volt boosting 6) but I keep my distance and won't try it myself. Sulfuric acid in the eyes from a battery explosion is not something I want to risk.

By making your final connection at the battery, an explosion from battery gas is exactly what you're risking - the final connection should always be made to ground well away from any source of fumes - whether gasoline or battery.

[RalphG]

Originally Posted by Randy in ca

By making your final connection at the battery, an explosion from battery gas is exactly what you're risking - the final connection should always be made to ground well away from any source of fumes - whether gasoline or battery.

That is true. I need to find a better, more accessible spot on the frame, away from the engine to make the final battery connection safely.
Or better yet, buy a new six volt battery.

[flatheadmurre]

Making the final connection at the auxilliary battery out in the open should work.
The gas buildup should be at the dead battry in the car charging.
Just dont do it on a freshly charged battery with gases from charging not wented out.
A trick i learned was to throw a wet cloth over the battery caps and went, works as a spark arrestor.

[Mark's 37]

Fired it up this morning. Sounds good, know knocks or banging. The problem was the crappy jumper cables which were too light gauge. Hit all the local autoparts stores early this morning and finally found a set of 2 gauge cables. Jumped the starter and off it went. Ran it for about 15 minutes at 1800-2200 rpm and now letting it cool down and then retorque the heads. Thanks for the help.

Very short video of unknown quality gives me an "invalid video" message when I try to post it. I'll try again later.

Edited: Found a set 2 gauge cables today.

[petehoovie]

Good for you Mark! When do you plan to change the oil?