Magneti Marelli / Harley-Davidson Part 1
Magneti Marelli fuel injection systems for Harley-Davidson
seem to get a somewhat of an unfair bad rap. From working on these systems I have found some common problems that create driveability and no run issues. The Marelli systems were used on Harley-Davidsons from 1995 to 2001, so the newest systems out there are already 12 years old. So for 12 years the pumps have been sitting in fuel, the o rings, rubber hoses and check valves have also been dealing with fuel. Fuel that in most cases contains 10% and up to 15% methanol. Watered down camel piss! Methanol, aka alcohol, does three bad things.
- Dries out rubber components
- Absorbs water
- Lack of lubrication properties
So fuel injection relies on:
- Clean fuel
- Proper fuel pressure
- Lubricated components
So fuel becomes contaminated by rust and pealing fuel tank liners and even bits and pieces of rubber components coming apart. That would be o rings and the interior of the fuel supply lines. On the early Harley/Marelli systems the gas tanks had steel feed and return lines inside (1995 to 1999) so you can get rust coming loose on the inside of the feed line, after the fuel filter. This allows junk into the injector side of the system. The contamination from the fuel tank liners and rust inside the tank are before the fuel filter, so that stuff should be trapped by the fuel filter and not get into the injectors, lines, regulator etc… However the fuel sock may let some smaller stuff into the pump and on occasion the fuel sock will disintegrate and large chunks of junk will get into the pump at this point.
Bikes that have sat for a long period of time with or with out fuel in the tank need attention. Just as you would clean the carburetor and stuff on a regular bike, your fuel injected bike needs the same attention. Even bikes that remain in service and have fresh fuel in them all the time need attention. A good maintenance plan that includes a good gas treatment is beneficial.
I like Seafoam. It is available at most auto parts stores. It’s a strong cleaner depending on how you mix it. Read the can. I’ve poured 1/2 a can into 5 fresh gallons of gas on dirty jobs. It cleans very well and also lubricates.
Marvel Mystery Oil is another good product available all over. Marvel is more of a maintenance additive that you wouldn’t use for cleaning a really dirty system, although it does keep systems that are clean and in use, clean and lubricated. Put a couple of ounces in about every 2 to 4 tank fill ups. Read the bottle.
It is a good idea to add Seafoam every 10,000 miles to keep systems clean. Seafoam is also a good fuel stabilizer for when a bike is going to sit for a while.
In summary Marvel Mystery Oil and Seafoam are good for regular maintenance.
This is not only good for all injected bikes, but also good for carbureted bikes as well. Actually I do this with everything that has a internal combustion engine.