Only 10V at starting.

Wiring, lights, heater controls, anything electrical..
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jimharold
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Only 10V at starting.

Post by jimharold »

Hello All,
I installed a Pertronix II with coil last summer. Over the winter it got harder and harder to start. Lots of cranking but took forever to fire. Once it rumbled to life it purred like a kitten and runs strong. At first l thought it was fuel related but looking down the carb a pump of the peddle sends 2 good squirts of gas down the intake. Then after reading a few posts I checked the voltage at the ballast resistor and got 10V during cranking. Following it back to the starter switch I had 12V in the run position but only 10V at the cranking wire while cranking. Coming out the back of the switch. Had to prove it wasn't the bulkhead connector. Ballast resistor bypassed with short 2 inch solid wire, .1ohms across wire. That should not matter on starting anyways.

So question is "Is 10V enough to start a 68' 318?"

Also installed new sparkplug wires last summer too. The timing is nice with the Pertronix at the flash the line on the balancer is rock steady. 7* advance gives second gear scratch and the best 0-60 time.

So any and all help wanted. I am off tomorrow and will test ideas out.

Thanks,
Jimharold

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my5thmopar
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Re: Only 10V at starting.

Post by my5thmopar »

I'm still wondering about the bulkhead. Was the battery and key side ballast in the key on run (dark blue wire) both at 12V(not running only on). More that about .5 volt you have a wiring issue. You should have 12V cranking (that's assuming the battery is still at 12v cranking) and then drops to 8-10 running. Are you using an aftermarket coil. If the resistance is low enough you don't use a ballast. I've used the Pertronix II and Blaster coils. The instruction said to remove it. The ballast reduces the current through the coil is reduced by the ballast while cranking. Old days was used to save the points/ECU during cranking and kept the coil from getting hot. Long day tired but, I think I got it right. Craig

jimharold
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Re: Only 10V at starting.

Post by jimharold »

Yes, 12V at the run side of the ballast with the key in the run position. And the battery is at 12V fully charged. And it is the flame thrower 2 coil I am using.

Please keep the ideas coming.
Jimharold

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my5thmopar
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Re: Only 10V at starting.

Post by my5thmopar »

jimharold wrote:Yes, 12V at the run side of the ballast with the key in the run position. And the battery is at 12V fully charged. And it is the flame thrower 2 coil I am using.

Please keep the ideas coming.
Jimharold
No ballast needed with flamethrower.

jimharold
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Re: Only 10V at starting.

Post by jimharold »

To keep the factory look I replaced the resistive wire in the ballast with a short length of solid wire. This I epoxied into the ceramic holder. In essence joining the crank wire and the run wires going to the coil. This is where I checked for voltage. With the key in RUN I read 12.5V, then cranking only 10.5V. You would think that is enough since when the battery gets old voltage drops. So what am I missing?

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Re: Only 10V at starting.

Post by cadman »

Electrical theory (so maybe not real life?) says that if you have that large of a voltage drop under load, either the power source is undersized and/or the load is drawing too many amps.

So, it could be a weak battery - have you tried to jump start it? Or, possibly the starter is starting to go? Seems like winter would be harder on your battery than on the ignition.

BB
Grandpa's '66 W200

If it aint' broke..., I probably haven't fiddled with it.

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my5thmopar
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Re: Only 10V at starting.

Post by my5thmopar »

What are we working on here? Well you already know auto electrical can be tough. You're going to need someone smarter than me but, I'll tell you what I know. BTW I had a hard start and it was bad Pertronix. The factory replaced it.

Did you have an original points or electronic distributor?
.....You said 12.5 in run position, then it was 12.5 at the coil? If any difference, you have a issue and it will show up worst when the amperage jumps during cranking.
Here some more stuff to check but, I really think you need to trace the path and find where the voltage loss is.
Clean all the connections
Battery and frame ground
Check ECU ground and ohm it to battery negative.
Any electric choke in the circuit on the coil or alternator?
Gap on the Pertronix
Some where along the path from the battery to coil has a bad loose connection. Check the schematic for the path
batt to fusible link to bulkhead to amp meter to ignition key wire big connector to key switch to then it goes back the other way to- ignition key wire big connector where the running wire(Blue one) to bulkhead to other side of ballast for key.

That's all I have.

jimharold
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Re: Only 10V at starting.

Post by jimharold »

UPDATE:

Pulled the ignition switch out and ohmed all the paths. .2ohms was the largest resistance of them all. Cleaned all the contacts and added grease to the switch connectors.
It helped! Not great but getting better. Started faster than the other day. Voltage at the ballast in crank position was up from 10.5V to 11.4V. So I am making head way. Have to go to work now, I'll take the bulkhead connection apart tomorrow and clean it next. And clean all the grounds I can find.

Thanks for the help and I'll post my findings,
Jimharold

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Re: Only 10V at starting.

Post by 712edf »

On one of my 70's W200 I had a special toggle switch that I'd flip On only while cranking. It tossed a full 12V to the coil, started perfectly.
Probably not feasible on your application due to its hokey appearance/originality.

Bucky
1966 W500
1975 W600
1978 W200 club cab

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Re: Only 10V at starting.

Post by jimharold »

Hey 712edf,

My 64' Chrysler 300 had a push button under the dash that my dad installed. I always thought it was an anti-theft device. Until it broke and the cap fell off. After that dad used a small glass salt shaker with a metal top to make contact for the button. That salt shaker stayed in the console for decades. Not until I reacquired the car in 2008 and swapped out the push button. Now I think dad was just cheap.

Drove the truck 43 miles to work tonight and enjoyed it all the way.

Cheers,
Jimharold
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Re: Only 10V at starting.

Post by Creepjohnny »

Cleaning all connections is a great start. Tighten and grease any loose ends. How old is your battery? I don't drive my vehicle very much so I keep them on a float charger. Keeps the Volts up. But sounds to me like your battery maybe a bit low. 14v on a battery usually crank at 12v. Battery may read 12v but that can be a little low for cranking.
Best of luck to ya!

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