I have a 04 fatboy and it’s firing only on one cylinder. Replaced coil and ecm however it’s not firing on both cylinders and advice on where to next

 

Are you saying you figured out it's a lack of spark rather than a fuel issue?

Which cylinder isn't firing?

Did you check for codes?

What led to you replacing the coil and then ECM? That information is important if you want informed suggestions on where to turn.

Helping to diagnose an issue via a forum is not easy. We cannot see, hear, or feel what you can. Anything you did to try and diagnose the problem is valuable information to those of us who are not there to see, hear, feel for ourselves.

 

Im guessing u have checked the spark plugs and wires?

 

New plugs and wires, coil new and even new. Could crankshaft position sensor be the culprit. It has aftermarket tsm and really can’t clear old codes

 

Do some basic checks before spending any more money.

Are you getting spark on the cylinder thats not firing?

Is the plug gapped properly.

If so is there compression? Just stick a thumb over the spark plug hole and turn the bike over.

If you have both of those check the intake manifold. Super simple to check. Start bike. Spray brake cleaner at the intake/head interface on the cylinder that isnt firing. Listen for a change.

All these are free, quick and good to rule out if not the culprit.

Report back.

 

There are several things it could be...

It's always better, and cheaper in the long run, to diagnose your problem rather than to just throw parts at it...

You'd be better off sharing what your bike is... including performance mods and other stuff like the aftermarket (Custom Dynamics?) TSM.

Tell us what happened when/how the issue started, what you have done to diagnose it, and what fixes you have tried...

There are a lot of smart people on this forum who could help narrow down the probable causes, so you won't have throw a bunch of money at it...

Did you ever check for codes?

NOTE: panhead pete and I were typing at the same time....

 

Bike is a 04 fatboy with carb no performance enhancing on motor tsm is only aftermarket on bike. I parked it one afternoon and we back later that night it would only run on res cylinder changed plug wire around and still only fired on ack cyl. Just been kids aggravating

 

Broken wire in the harness somewhere to that side of the coil perhaps?

 

Good info, thanks.

Is this lack of spark intermittent or all the time? You mentioned "old codes"... what codes did it have?

Electrical issues aren't my comfort zone, but I can usually work through them. There are others better versed than I am with electrical stuff that will chime in..

To answer your earlier question, I do not believe your issue could be the crank position sensor. I do not believe you would get any spark at all if it was acting up. You report spark on one cylinder.

This is a sudden event, suggesting something may have broken or got loose.

You say you have new plugs, wires, and coil since the issue started, and the issue still persists. You can start with checking these (sometimes you can get a new bad part), or consider them fine and work backwards from them.

Your coil is obviously getting something from the ICM since you have spark to one cylinder. I would be checking from the plugs backwards, to see where there is an issue. You could start by checking all electrical connections, looking for bad connections, dirty connections, bent connector pins and/or damaged wires. I would also be checking for proper voltages from pins in the ICM. Minus knowing proper voltages from the ICM, you could start by checking wires for continuity, looking for breaks. Eventually, I would be testing the ICM itself.

I would need a diagram to deal with this..

At this point you might want to go to the Harley Service Information Portal website, and enter your VIN. It should bring up the wiring diagrams for your bike.

https://www.hdforums.com/forum/newre...ply&p=22136203

You could also get a used copy of the 2004 Harley Softail Electrical Diagnostic Manual #99498-04 to get both diagrams and diagnostic charts. I always buy an HD factory service manual and HD electrical diagnostic manual for all my bikes. I keep them as I sell bikes, for reference. I don't own one for a 2004 Softail.

https://www.ebay.com/itm/205575914874

When dealing with electrical issues, I try to be thorough, systematic in my approach, and persistent. With the info in the electrical diagnostic manuals, and sometimes forum assistance, I will usually prevail.

Those who know this stuff from memory will hopefully offer their assistance.

Good luck with the repair and keep us posted on your progress...

 

i greatly appreciate your helpful feedback now know there to look back at