2000 Ultra

I went for a ride yesterday and noticed that the check engine light would come on when accelerating hard (4000+ RPMs) and then go off shortly after I got under 3000 RPMs. Has this happened to anyone before and, if so, then what was the cause? The bike will not return a code because whatever condition is causing the light to come on corrects itself when I stop accelerating and start cruising.

FYI - I considered that my fuel pump, which as far as I know is original to the bike (i.e., 25 years old), was going but the bike did not feel like it was sluggish at the higher RPMs.

Any suggestions would be appreciated.

V/r, Bob

 

I’m no mechanic but has the fuel filter been replaced? This was mine after 7 years. Not sure if a restricted filter would cause your issue but it would make sense.

 

Oh oh. My Ultra is 22. I'd better check the fuel filter.

 

Thanks for the reply. I probably should have clarified that I replaced the fuel filter, the screen bag at the bottom of the pump, and the supply line from the pump about 2 years ago.

 

Two years on fuel filters... tells us exactly zero in regards to the amount of use they've seen. could have 10 miles and only ounces of fuel thru, could have 40,000+ miles and hundreds of gallons through it in that time period.

Likely based on the average rider the fuel filter is fine, unless you got some bad/ excessively dirty fuel, is your tank rusting? Are there any other symptoms associated with the check engine light?

 

Regardless of any of this, I would replace pump and filter, simply because 25 years old. Or you could spend hours on the side of the road, late for work, talking to cop,.
Not positive MM but should it have histortic codes? Should after the light goes on for start up, go on again for a code that occurred?

 

If it threw an engine diagnostic code (check engine light came on), and the issue clears itself, it should still show a historic code for several engine cycles before that historic code clears itself...

Sorry if you already know this, but....

Did you check for codes via the data port, jump wire, and count the flashes technique? Or did you just check using the speedo console?

Many people don't realize that on the early twin cams, you only get speedometer codes through the speedo console, and have to use the data port & jump wire technique to get the engine diagnostic codes ...

I offer this info because based on your description, there should be a historic code that could help lead you to your issue. It could pinpoint whether your issue is fuel or spark related and narrow your diagnostic search...


EDIT- I just realized you have an MM EFI setup. I know the above info to be true with the Delphi EFI systems, but I have never worked on, or read the electrical diagnostic manual for an MM EFI system. Sorry, but I can't be sure about my info for MM systems.

 

I have another motorcycle I ride, so there are only about 1K miles on the new filter. There is no rust in the tank. When I did the filter I removed everything in the tank (fuel pump, lines, etc.) and washed out the tank with hose. There was some fine rust/sand at the bottom of the tank when I did that but cleaned all that out with hose and shopvac. I have not noticed any symptoms other than the light.

 

How are you checking codes? The speedo won't have any codes for the ECM.. IIRC you need to short to pins on the diag connector and count the flashes on the motor light.. I'm no expert on Magneti Marelli tho..

 

One person that's an expert on this is @Ed Ramberger . Hell get a notice for me tagging him.. He should have some info..