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Old 05-19-2005, 06:59 PM
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Problem with a 350

Ive got a 76 c10 that i have been working on ... The ignition module went bad so i replaced it and while i was at it i changed the coil,dist. cap and rotor. She started up just fine and will idle nice but as soon as i give it more than 1/2 throttle she starts missing and spitting back up through the carb.

I back pedaled and changed the dist cap,rotor and coil to see if either of those were the problem and it still does the same thing ...

Could they have just sold me a bad module ? Or does this sound like a different problem ?

Thanks in advance for any suggestions ...

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Old 05-19-2005, 09:26 PM
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Runs bad off idle

Sounds like you may have a worn dist.shaft and it could be slipping in the case. Set your base timing at idle then run up the throttle and then go back and check base timing..see if it has moved....
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Old 05-20-2005, 05:52 AM
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Firing order

Doc here,

Check your fire order... 1 8 4 3 6 5 7 2, direction of rotation right (clockwise) If 5 and 7 were reversed (a common error) It will act much the way you describe..

If that's good check to be sure none of the module connections or mag pickup wires are hitting anything when the advance plate moves forth and back.

Check to see that your mechanical advance isn't stuck and rusted advanced...

Disconnect and plug your Vacuum advance vacuum line, Hook up a timing light and set your static timing at about 12 to 14 degrees..if that's good, you may have a defective module..have them (the auto parts store) test it several times to heat it up...Did you clean and apply new heat sink compound on the last one? Could Be the whole problem.

Doc
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Old 05-20-2005, 06:16 AM
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Doc is "right on" with the suggestion about the 5-7 switch. I have been burned by that several times, assuming it was correct while trying to diagnose a problem.

Vince
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Old 05-24-2005, 05:03 PM
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Since you replaced everything else, I'd say my first bet, is the pickup coil. It's in the bottom of the distributor, and you have to remove,and dissasemble the distributor, to change it.

A tired p/u coil can give all kinds of wierd symptoms, from a cold miss, to a mid throttle backfire, to no fire at all.
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Old 05-24-2005, 07:56 PM
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Filter Capacitor

Doc here,

Also a Breaking down (Leakey) Capacitor (both and/or Either) on the Coil circuit or the distributer Circuit Can give you the same symptoms...Locate it, (if so equipped)Disconnect it and try again, If it runs OK get a new one..

A shorting Tach/Wire Can also Cause Similar problems on an HEI (as well as others) ..Disconnect the tach wire, does it go away? If yes troubleshoot the tach circuit or replace The tach.

Doc
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Old 06-01-2005, 04:40 PM
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It turned out to be a bad module ... I checked everything else as advised and no improvement so i took it back, They tested it and sure enough it was bad, Funny thing is it was only a week old and they wont give a refund on electrical parts. bah ... It was only 20 bucks so that wasnt too bad.... Thanks again
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Old 06-01-2005, 05:57 PM
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Cure

Doc here,

Thanks for posting back with the cure!

Can be helpful for the next guy.

OBF Modules are Quite Common now a~days! I always recommend that when replacing them, have it tested BEFORE you leave the store...SEVERAL times so as to heat it up good and well...This will insure that it will work , and not fail under load...(If you properly install it).

As for the parts store not exchanging the module (look on the box it came in, I think some have a printed warranty) If they won't step up to the plate...go some where else...most stores I deal with understand and will replace an OBF, no questions asked.

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