backfires when i turn key off

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bigtommy

bigtommy

old school power
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chambersburg, PA
i started my valiant today for the first time in mouths(just put new wiring harness in) it took a little to start it but it started up twice. now it wont start and then i turn it over and stop and turn key off it backfires out the exhaust. it will backfire every time i try to start it and turn the key off. NEED HELP!!
 
Did you pull the distributor? It also may be loading up and when it fires it's blowing out the exhaust.
 
Badsport said:
Did you pull the distributor? It also may be loading up and when it fires it's blowing out the exhaust.
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yea pulled the distributor, re did timing. its a brand new distributor. and when i turn the distributor 180, it will back fire throw the carb.
 
It must be loading up on gas and when it fires it backfires through the exhaust. Have you checked your plugs to see if they are soaked?
 
no i didn't check the plugs, ill check them tomorrow. i did notice, gas fog in the carb after it back fires
 
When you turn the key off it drops the field in the coil causing it to to fire any random plug at any random place in the timing.
Unburned fuel in a cylinder will fire if it's the cylinder that got the random spark.
I have my timing advanced right to the edge, and my engine will do that once in awhile.
If it's popping back through the intake when you shut it off, try backing the base timing a little.

Maybe?
 
OH YEA, and it would explain the loose fuel that's getting ignited on shutoff.
 
Well it may start once or twice, but if your carb is out of whack you will be back to square one before long. If it does fire up then you know the plugs were bad, once you determine that then you can address the reason why it's happening.


Also you said you had the distributor out. Did you get it back in properly? It could be a tooth off if you disturbed the gear which would give you fits. Also make sure your wires are oriented correctly on the cap and going to the proper cylinder.

Keep us posted here, you'll get it.
 
i would agree its dumping fuel. if it was popping through the carb after you flipped it 180* , you had it right the first time. im betting the plugs are soaked with fuel.
 
i put new spark plugs in today. the passenger side ones were soaked but the driver side were fine. why would the passenger side ones be soaked but not driver side
 
bigtommy said:
i put new spark plugs in today. the passenger side ones were soaked but the driver side were fine. why would the passenger side ones be soaked but not driver side
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What carb and manifold are you running"
A dual plane manifold could do that since left and right banks run on separate sides of the carb.
 
TrailBeast said:
What carb and manifold are you running"
A dual plane manifold could do that since left and right banks run on separate sides of the carb.
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its a 600 holley vac sec. with a edelbrock street master.
and it ran good when i had it running. i didnt do the timing when it was running though. but it would idle without me reving it up.
 
I always like to go back to what was recently touched/modified, so i'd want to double check the wiring, especially the coil, and distributor. The Street master is a single plane iirc. Hard to figure why one side plugs would be wet. I could see front half (primary) or rear half (secondary) if a float was stuck/sunk.

Don't chop my head of guys, but i have to ask.......How old/miles is on the timing chain?
 
Back to basics.Older Holleys ,when they backfire ,tend to blow the power valve.I don't know if you have ever done any work on that 40 dollar carb.Others will chime in,but that would be ,where I would start Big Tom.
 
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