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post #1 of (permalink) Old 12-30-2002, 07:55 PM Thread Starter
 
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Backfire thru carb. - Advance or retard?

If search wasn't "unavailable" I'd use it and look it up for myself.

Every once in a while when driving I'll get a backfire through the carburetor.
I can't seem to remember if this means the timing is too far advanced or too far retarded.
Right now I'm sitting at about 9* BTDC @ 1000 RPM.
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post #2 of (permalink) Old 12-30-2002, 08:23 PM
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Re: Backfire thru carb. - Advance or retard?

i think normally you want to advance the timing if its backfiring through the carb....

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post #3 of (permalink) Old 12-30-2002, 08:53 PM
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Re: Backfire thru carb. - Advance or retard?

Possible problems I can think about that need to be ruled out one by one:

1. Defective accelerator pump
2. Weak or broken valve spring
3. Low Compression
4. Cam-to-crank timing off
5. Burnt/damaged valves or seats
6. Crossed plug wires
7. Shorted distributor cap
8. Carbon tracking on plugs
9. Ignition timing off
10. Low fuel pressure
11. Worn cam lobes
12. Vacuum Leak (loose intake manifold)
13. Carbon deposits on the pistion or intake valve
14. Lean mixture
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post #4 of (permalink) Old 12-31-2002, 08:02 AM
 
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Re: Backfire thru carb. - Advance or retard?

My money would be on a crossed plug wire....only if you had recently worked on the ignition system. Did you change the plugs before this started happening?
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post #5 of (permalink) Old 12-31-2002, 01:54 PM Thread Starter
 
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Re: Backfire thru carb. - Advance or retard?

I did put new plugs in recently, but they were the same exact ones I had in there....same brand and part number.

The plug wires are correctly placed in relation to which tower goes to which cylinder on the engine.
However, the way that the distributor cap is.....all the wires are pretty much laying all over eachother.
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post #6 of (permalink) Old 12-31-2002, 02:17 PM
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Re: Backfire thru carb. - Advance or retard?

Wires don't always have to be switched to create crossfire -
but switching is definate!
Plug wires laying parallel for too long a distance causes
cross induction - same symptoms. The magnetic field around
the correct wire induces enough voltage in the wire next to
it that it fires too - in the wrong cylinder at the wrong
time. Tying wire so they look neat looks good, but doesn't
work so well.

Try separating the wires better. Also look for whitsh marks
along each wire - indication of insulation breakdown. Spark's
jumping through at that piont.

Or - When you changed the plugs you may have inadvertantly
broken the connection at the end. Now it's an open wire -
or partially open.
A partially open wire is much harder to fire - sometimes it's
easier for the spark to jump across the terminals in the
cap, or even jump to the wrong wire.
The cure is replace that broken plug wire - or re-end the
terminal.

Sometimes the symptons are under acceleration, deceleration,
cruise or even idling - unpredictable when it does it.

And it could just be an insulation problem, occasionally the
spark jumps to ground somewhere. Easy way - usually - squirt
water around with a Windex spray bottle on the ignition wires,
plugs, cap, coil etc. When you feel a tingle or hear a misfire
you found it.
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