70hp chrysler wont start just backfires

dutch420

Petty Officer 3rd Class
Joined
Sep 16, 2012
Messages
84
Decided to get to a motor I picked up a few years back. Hooked it all up and had no spark. I swaped over a spare cdi still no spark , so I cleaned points and now I get a motor that wants to start but wont. It also sometimes has a bad backfire thorugh the exhaust. Im a lil stumped. I will be doing a carb clean. I noticed that #3 carb leaks gas from the over flow when primed and ball does not get "hard" im assumeing because of this. Anyone have any ideas about whays goin on
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
First off I need to know if that Chrysler has the Motorola CD ignition with a distributor or if it has the Prestolite with two CD boxes and three coils. If it has a distributor I need to know if it has the electric eye (two wires on the dist. side and may say "Electronic") or points (one wire on the side.

When working on an engine that old, ASSUME that anything that can be set incorrectly IS. Set every spec back to factory before even trying to start the engine.

I was working on an old Chrysler 90 that the owner told me would not run. He replaced the carbs and ignition components. He had on Summit after-market plug wire which were incorrect. Rather than go crazy trouble-shooting, I replaced the complete ignition, including distributor, with one off a known running engine. It fired first turn and ran with no problems.
 
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SSSuper83

Petty Officer 2nd Class
Joined
Feb 23, 2010
Messages
132
I spent all weekend chasing the exact same problem on my 78 105hp with Motorola CD and breakerless ignition. I thought it was bad fuel at first, cleaned both carbs and entire fuel system, nothing changed. Runs for two to three seconds and backfires so hard it kills itself. Don't want to keep trying and risk damaging a rod or bearings...I understand the "electric eye" ignitions are pretty suspect?
 
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