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Old 04-05-2007, 08:27 PM
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Electric choke voltage

I have an Edelbrock carb on my 350 and I have it running very nicely. The only problem is that it takes a long time to open the electric choke. I checked the voltage to the choke and it is only 6 volts. The power is taken off the coil.

Do I need to get 12 volts to it? I opened it a little which will be fine for the spring and summer but I am not sure it will work well in the winter. I can go about 8 miles the way it was before it fully opened. I could tell by the reading on my vacuum gauge. I was low until it opened all the way. The t-stat doesn't open until about the same 8 miles. It runs very cool even when pulling a trailer in the summer. I would like it to heat up a little faster. I have a 180 t-stat. Has anyone tried "hotter heater"? If so does it work and where can I get it?

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Old 04-05-2007, 08:34 PM
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Check out this thread.
electric choke problems
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Old 04-05-2007, 11:32 PM
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Is there supposed to be only 6 volts coming from the coil? I have a drop in MSD dizzy and MSD coil. Both are new.
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Old 04-06-2007, 03:08 AM
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Doc here,

A non HEI , GM in cap type coil will have only 6 to 9 Volts at the coil + side. This is because it has a ballast resistor in line with the coil to keep the coil and module from burning up (usually..not always).

If your trying to run both, I suspect both are suffering performance wise, coil and choke heater..

You Really Should never connect ANYTHING to a coil + side, they draw enough current on their own without current sharing with something else..and can make your $1000 performance Ignition run like a $59.00 EBAY HEI..

The Proper (and GM way) to connect a choke heater is with a relay through the field winding of the alternator, Where it only heats after start up, not just sitting with the key on while you attend to the business of loading up the car, scraping ice..belting in the younguns Ect..so it won't crank on an open (pre~heated choke).

Here is an Example of a GM choke heater Circuit from the manual:



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Old 04-06-2007, 05:56 AM
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definitely 12V to the choke (only with the key in the on position).....

6V at the coil=??? what is the car, how old are the harnesses???

(my gut feeling guess says your coil + wire has a 1.5ohms resistance wire for a points ign plus the approx .8ohms in the coil to drop it that much???)

agree with doc'.....ign only!.....on the coil plus terminal.....
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Old 04-06-2007, 08:47 AM
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The truck had a points dizzy when I bought it and I put in the MSD with MSD coil and new wires. I don't see a ballast resistor. I'll pull the wire from the coil (which is where it was when I bought the car).

My perforemance has been good but I am not getting the greatest gas mileage. Plugs are burning well. Light brown.
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Old 04-06-2007, 08:59 AM
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Doc here,

Not knowing what type of vehicle it is on, and given the fact that IT had points before my bet is on a factory stock Ballast resistance wire..It traditionally is white cotton clad, and MAY be marked "resistance wire DO not cut " on the insulation..going to the coil +..

Another option is the coil may have it's own internal ballast..if it were matched by MSD..droping the operating voltage from 12 to 6 or 9 volts..check your installation diagram and instructions for that info..

The third option may be that the combined load of heater and coil may be swamping the current on the circuit..disconnect one or the other and see if it rises to 12 volts with only one device on the line.

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Old 04-06-2007, 09:14 AM
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The wire is pink and appears to be a newer wire.

I checked the voltage with the choke disconnected and it was still 6-9 volts at the coil.

I bought the dizzy and coil on ebay. I got the instruction for the dizzy (it was still new in the box) and will check the instructions

thanks
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Old 04-06-2007, 12:39 PM
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Merts, The Doc is right on. You have a ballest resistor or a resistor wire both are bad. You need to run a heavy wire from the "IGN' side of the switch or fuse block directly to the HEI cap. My 81 Monte Carlo had a oil press. sender with two terminals, one for the oil lite the other went to the choke heater. (No oil pressure, No power to the choke.) It only costs a few dollars at a parts store. Wayne
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Old 04-06-2007, 07:32 PM
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I took the coil wire off the coil turned on the key and got 12 volts. I pulled the wire off the coil to the choke and ran a new wire to a switched source I found under the hood. I am now getting 12 volts to both. Choke opened right up.

Still not sure why I was reading 6 volts. I checked the wire to the choke that went to the coil and it allowed 12volts. Oh well fixed now.

Thanks for the help.
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Old 04-06-2007, 11:43 PM
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Doc here,

The Choke heater element was probably load sharing with the coil, and acting as a ballast resistor...

Glad to hear you got it though!

Curious..Post back and let us know IF the mileage gets better..good info to know..

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Old 04-07-2007, 06:56 AM
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trivia(?)
a bright pink wire with a very soft insulation is a typical Ford 1.5-2.0 ohm resistance wire ussually wound up under the dash
"back in the day" it had a cotten cover as a heat insulator

mertz,
next step for mpg now that the idle voltage* is fixed:

if you have the plugs gapped at .035 or so DO contact MSD and find out what the recommended plug gap is for that dist and coil...
"IF" you can use a bigger plug gap (.038?) the coil will build to a much higher voltage before it does jump the gap making a bigger stronger spark
.035"=10,000V roughly
.038"=12,000V roughly
.042"=15,000V=HEI roughly
DON'T exceed the mfg recommendation

the creamy brown plugs are indicating (as much) that the A/F mix is correct.... not that the spark energy is optimum for a complete burn....

can be 2-3mpg just re-gapping the plugs

*if you had started the truck and rev'd it to about 2500 there would have been 12V at the coil....the alt amp output overpowers the resistance.....thats why the plugs look good....it's only 6V at idle

again, what is the truck?
I get very nervous posting info without knowing what I'm dealing with....
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Old 04-07-2007, 10:08 AM
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The truck is a 72 Chevy with original 350 and 350 trans. I added the Edelbrock EPS intake, Edelbrock 600 cfm carb, MSD 8360 Dist., MSD coil, 8mm wires, ceramic coated header, flow thru dual exhaust, roller tip rockers, 1" carb spacer and Edelbrock valve covers.

It has factory air and is an original 143,000 mile 3/4 ton 2wd.

I trimmed the ends of the plugs (old hot rodder trick) so that the spark is more consentrated in one place than bouncing all over the electrod. I have them gapped at 35. Now that my coil is correctly wired I will try to open them up a little.


I am getting ready to take it out this morning. I should know pretty quick if I am getting better mileage. It is a 60 mile round trip into town.
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Old 04-09-2007, 08:51 AM
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Took the truck for a test drive but did a lot of stop and go driving so mileage is down. I will do a fillup and see what it is and let you know. The vacuumm came right up after a mile or so. Weather was in the mid sixties so that helped as well.

The one sided effect of the change is that the truck started with the first turn of the key before the choke was corrected now I have to crank on it a lttle. It was like fuel injection, just tap the key and it would start.

Do I need open my idle screws a little since it is probably running a little lean now?
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Old 04-09-2007, 12:03 PM
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You will read battery voltage on the end of an open wire, resistor or not. Without current flow, there is no voltage drop across a resistor. Check your voltage again at the coil with the wire hooked up to assure that it is 12V. If not, minimize doubt and run a new wire.

Cam
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