Only firing on one cylinder!!! - Harley Davidson Forums: Harley Davidson Motorcycle Forum
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Old 04-20-2010, 09:17 AM   #1 (permalink)
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Only firing on one cylinder!!!

My 2001 fatboy is only hitting on one cylinder. I've tried replacing the plugs. No luck. I can't get a hold of a new plug wire for a couple of days, but I checked the back plug wire with an ohm meter, and it looks like I have good resistance. (I checked it against another wire that doesn't fit the bike. I'd like to get it to the mechanic and have it looked at, but funds, and lack of ability to drive are preventative. Any ideas?
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Old 04-20-2010, 09:21 AM   #2 (permalink)
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Quote:
Originally Posted by Guy Rand View Post
Any ideas?
Switch the plug wires AT THE COIL and see if that makes a difference. If it does, then you have a bad wire, or a bad coil.

Test the coil.


http://www.harley-davidsonforums.com...your-coil.html

If coil fails, replace coil.

If coil passes, replace wire.

You can get wires for $8 at AutoZone, if you get the Accel (yellow) repair wire and not the entire kit for a V-8 engine.

New SE wires are only $19 a set.

After you figure it out, please return and tell us what it ended up to be.
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Old 04-20-2010, 10:56 AM   #3 (permalink)
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Tried switching the plug wires at the coil, and got a horrible mechanical noise. Not sure if it was a result of my battery dieing or not. Switching the wires shouldn't cause any mechanical issues should it? Other than improper firing order. Will it even run if I switch the wires? Not doubting you, just trying to learn a little.

Thanks
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Old 04-20-2010, 11:15 AM   #4 (permalink)
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Quote:
Originally Posted by Guy Rand View Post
Tried switching the plug wires at the coil, and got a horrible mechanical noise. Not sure if it was a result of my battery dieing or not. Switching the wires shouldn't cause any mechanical issues should it? Other than improper firing order. Will it even run if I switch the wires? Not doubting you, just trying to learn a little.

Thanks
If the bike has OEM ignition, it's dual fire, and there is no "firing order". If the ignition has been replaced with a single fire, then it will make a difference.

I can switch the wires on my bike and no difference is noted, because the plugs fire twice on OEM coils/ignition.
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Old 04-20-2010, 11:45 AM   #5 (permalink)
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This is twin cam info:

This is for a carb motor…
the plug wires should range in-between 5000 ohm to 11600 ohm's of resistance
this is based on a wire that's in the 20 inches long.

this is for an efi motor…
length 7 1/4 inches 1500 to 4500 ohms of resistance (front)
length 19 inches 4500 to 12000 ohms of resistance (rear)

on the coil…
always have one ohm meter wire on the 12v terminal
the other wire will check both the primary side and the secondary side
(if you don't know the difference... the primary side is the low voltage side or the power to the coil side... the secondary side is the high voltage side or the spark plug side)

the primary side:
has 0.5 ohms to 0.7 ohms of resistance
the secondary side:
should have 5000 to 7500 ohms of resistance

if the coil is outside this range... get a new coil

Maybe I’m still assuming too much... you have 3 or 4 wires going into the coil... they are labeled position A, B, C, and D. "D" is dependent only on the year. Don’t worry about "D" for now, it's for the ionization.

primary side:
A is the Front primary
B is 12 volt in
C is the rear primary

secondary side:
plug wire 1 socket is the secondary
plug wire 2 socket is the other secondary

hope this helps
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Old 04-21-2010, 09:39 AM   #6 (permalink)
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Switched the front plug wire to the back, and it fired. I think I can get a hold of a new set of wires tonight. I'm hopeful.
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Old 04-21-2010, 10:49 AM   #7 (permalink)
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could you check that bad wire with an ohm meter and post it... I would like to know what it is... along with the length of the wire.

thanks
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Old 04-21-2010, 05:31 PM   #8 (permalink)
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It was my back wire which might be 6" or less. The reading I got was 2.8, but that was the same reading I got from a good wire with a similar length on my car...(the coil wire) So I couldn't really tell from the ohm reading that it was bad.
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Old 04-22-2010, 06:55 AM   #9 (permalink)
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It very well could be that the CKP ( crank position sensor ) is bad .
I don't know what you have for test equipment but a simple test light will suffice . Connect the test light clip to the neg. batt. post . Disconnect the coil connector and with the ignition on check for voltage at the B contact , it should light the test light . Now hook the clip of the test light to the pos. post on the battery and probe the A and C connector pins while cranking the engine , the test light should flash on and off at both pins . If only one flashes or you see uneven flashes the CKP is culprit or one of the wires is open .
Probe the connector pins gently so they don't get damaged .
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Old 04-23-2010, 12:53 PM   #10 (permalink)
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Changed the plug wires out, now she's back to running like a scalded dog!!!
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