Running on one cylinder
A bad fuel injector
Replace fuel injector
Harley Davidson fuel rail
Bad, or blocked fuel injectors are not uncommon. If you own a fuel injected Harley Davidson that begins running on only one cylinder, this may be the case. Running on one cylinder, however, can be caused by a number of other issues that will need to be ruled out first.
Recently, we had this 2008 XL in the shop. The customer explained that it seemed to have a loss of power and was running “rough”. We quickly determined the m/c to be running only on the front cylinder. This, because of the simple fact that; the exhaust emitted from the front cylinder was hot. The exhaust from the rear was only warm. Mostly common sense.
Next, we wanted to determine if the issue was electrical or fuel related. The quickest and easiest thing to do is to check for possible stored diagnostic trouble codes. Often times, a stored code can either lead you directly to an accurate diagnosis or, at least, give you some type of clue that can lead you in a logical direction. This time, however, the m/c did not have any stored codes.
Next we decided to use a spark tester to check for spark at the rear plug. We found plenty of spark and were now able to confidently determine our issue to be fuel related.
A fuel pressure test showed us a good, constant 60 pounds of pressure being delivered to our injectors.
We could now determine that the rear injector on the XL was inoperative. At this point, you might need to think electrical again; but when turning on the ignition and switching to “run”, we could physically feel the injector functioning. No need for the electrical manual today. We took it one step further. We wet the injector and manually pulse powered it on the bench above a plain piece of paper. No fuel to be seen.
There are a number of high quality injectors available for Harley-Davidsons. This time, our customer requested that we install Fueling injectors. Injectors should always be replaced in pairs. We also replaced the fuel rail (with the correct OEM replacement), intake seals and spark plugs.