Problem with Mandy’s Road King.

Mandy’s Road King is a 1999 with Marelli-Magneti fuel Injection. It has a set of Rinehart True Duals on it. That was the only modification from stock. It has always ran well.

We started off on the bikes on Tuesday evening and just after she pulled onto the main road she went through the first few gears slightly aggressively and then got a simultaneous miss and “Engine” light. We were about a quarter mile from the house so we turned around and came home.

I checked the ECM codes and it was throwing 25 (rear coil). I thought that made sense because I had already told her it sounded like it was running on one cylinder and it smelled like it was running very rich. I restarted it and the right exhaust (front cylinder) was warm, the left exhaust (rear cylinder) was cold. Still making sense.

So I went online and started looking for a coil. Found the part number called a couple of local dealers 5-7 days to get the part $108. I wanted to find someone to overnight it to me or that had it in stock so I kept looking. I found it a lot cheaper than my local dealer, but still couldn’t get it overnight. I eventually found the Screaming Eagle replacement for my coil for $38 at an obsolete parts vendor, $28 to overnight it to me. So I ordered that and installed it. Put everything back together and now it was throwing the code for the crank sensor (41) and the rear coil (25) still only running on the front cylinder. Because of how it works a crank sensor didn’t make sense (one coil/cylinder working perfectly the other not working at all) but I’ve seen strange things with electronics so I went with it. A mechanic at the local dealership did find a hairline crack on my crank sensor when I was picking up the replacement part so I was skeptical but hopeful.

I installed the new crank sensor, code 41 cleared but I still have code 25 and the rear coil/cylinder is still dead. I have checked the wiring between the ECM module and the coil no shorts, no opens.

At this point I’m all out of bright ideas.

Any suggestions (other than dumping the fuel injection and installing a carb) would be appreciated.

 

1999 Road King
M & M Fuel Injection
Rinehart True Duals
I guess no fuel adder, power commander etc.
miles ?
Look at fuel injector wires.
There were postings in the past for that year and frame style of the wires to the fuel injector being tied back too tight.
The tightness eventually caused the wires connected to fuel injectors to break internally.
The insulation on the wires looked fine but wire was broken inside the insulation.
Review for continuity at the injector wires with a digital voltage meter.
You are looking at an area within 6 inches of injector.
You identified the cylinder so isolation of area should be easier.
Your year and model frame also had an issue with the bracket that holds the vehicle attitude sensor (a tip sensor)...basically cuts the motor when tipped over but due to bracket issue... the bike would shut-off over bumps....nothing wrong with the tip sensor...issue is bracket.

 

I will check that this morning but would a broken wire to the injector throw a coil trouble code?

 

Someone suggested that a temperature sensor could cutoff the rear cylinder, but I thought that was only on much later models with "parade mode". Does anyone have any experience with that?

 

I could be wrong but i thought parade mode was only on delphi bikes not M & M fuel injection.

 

First things first, make sure that the battery is fully charged. Have it load tested at an auto parts store. I don't know how many "electrical" issues I have seen on an EFI bike that traced down to a battery on its way out.

You should try switching the plug wires. If the rear cylinder works, and the front begins to misfire then you know the ECM is good, and the problem probably exists either in the injector wires or the plug wire.

Check the spark plug wire for the rear cylinder carefully. There is a thread on here somewhere where the wire looked fine, but it was broken and corroded when he stripped back the insulation.

Besides a continuity test you can do a wiggle test on the rear injector wire. If the cylinder begins to fire when you wiggle the wire you have found your culprit.

 

larsfum is right on-- swap spark plugs as well. Always check the easy stuff first!

 

That was my understanding as well.

 

I've done all this except the plug wire. To be honest I thought of that but had already put the tank back on and didn't want to take it off again. Since a bad plug wire would either send the discharged spark voltage to ground if it was shorted or nowhere if it was open, and that happens on the back side of the coil after it has charged and discharged would a plug wire throw a coil fault code?

 

Probably. I assume that the ECM is measuring not only whether or not the coil sends a spark signal, but it is probably also measuring the resistance of the signal as well. If the wire is pooched it would not have a high enough resistance, and the ECM would toss a coil code.

You do not need to remove the tank to switch the plug wires. Simply move the wire from one to the other at the cylinders.