MM injection issue
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1st Gear
Joined: Feb 2018
Posts: 5
Likes: 1
From: Texas
MM injection issue
Are there any MM injection guru's here? Ive got a 98 Road King with the MM injection and having a runability issue. Starts and runs fine initially, will rev as normal when twisting the throttle and will run for any given amount of time while parked. I purchased bike as a wreck. Replaced parts needed to run. Bike had a horrible stumble just off idle under a load. remove all tins for paint and pulled intake. Found seals on intake on incorrectly and fixed that issue. also replaced pressure line from tank. Cleaned intake and reinstalled. Received tins after paint and reassembled the tank with pump and new internal injection type rubber hoses. sealed with new gaskets. Got bike back together and purged the fuel system. Started the bike and stumble is gone. Rode bike down the street and ran great for the first half mile. Went through 4 gears pulling hard through all 4 at or above 3500. Turned around to head back, and bike wouldn't rev above 3-3500 without backfiring through intake and exhaust. As if its running out of fuel. Didn't have this issue prior to removing pump and filter. It did have the stumble but would pull through the RPM band. ANY insight would be greatly appreciated.
Stellar HDF Member
Joined: Jan 2009
Posts: 2,578
Likes: 463
From: On a Lake, not far from the Gulf
How many miles, and did you swap out the fuel filter when you did the tank? Do you have the FSM. There are diagnostic flow charts in it. First thing I would check is the crank position sensor connector located behind the right side cover. It is barrel shaped. They will sometimes work themselves loose. Then you get intermittent fits, or no fire. Clean the contacts, and cross zip tie it together so it will not come apart.
If that's not the cause then here's my to do's on any M&M EFI issues:
1) Make sure the battery is good. Have it load tested. Also inspect the cables, and make sure they are carrying up to snuff to carry the load.
2) If you have a tuner, take it out of line, and see if it runs fine without it. It will be a bit lean, but not enough to hurt it for the short time you need to test it.
3) Clean the throttle body, including the two air bleeds at the top of the mouth. Careful, they spit back.
4) While you have the AC off, clean and inspect the IAC motor. Make sure it moves after you shut the bike off, and shortly after it fires up.
5) Look under the nosecone for any dripping brown goo. That would be your Cam Position Sensor taking a dump. If you still have the rivets holding the nosecone cover on chances are it is original, and probably going if not ready to go. The new sensors use a black epoxy sealer.
6) If none of that works you can check the Engine Temp Sensor located on top of the forward jug. You can test it with an ohmmeter, or replace it for insurance.
There's a few places to start, but my money is on the Crank Position Sensor connector.
If that's not the cause then here's my to do's on any M&M EFI issues:
1) Make sure the battery is good. Have it load tested. Also inspect the cables, and make sure they are carrying up to snuff to carry the load.
2) If you have a tuner, take it out of line, and see if it runs fine without it. It will be a bit lean, but not enough to hurt it for the short time you need to test it.
3) Clean the throttle body, including the two air bleeds at the top of the mouth. Careful, they spit back.
4) While you have the AC off, clean and inspect the IAC motor. Make sure it moves after you shut the bike off, and shortly after it fires up.
5) Look under the nosecone for any dripping brown goo. That would be your Cam Position Sensor taking a dump. If you still have the rivets holding the nosecone cover on chances are it is original, and probably going if not ready to go. The new sensors use a black epoxy sealer.
6) If none of that works you can check the Engine Temp Sensor located on top of the forward jug. You can test it with an ohmmeter, or replace it for insurance.
There's a few places to start, but my money is on the Crank Position Sensor connector.
Last edited by larsfum; Feb 1, 2018 at 04:25 PM.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,621
Likes: 6,441
From: Honah Lee
This system in like a semi digital carburetor with a sprayer. What is cool is with a good service manual, a $20. volt/ohm meter and a Harbour freight hand vacuum/pressure checker, you can check everything.
Even on line on YouTube, there is some excellent videos of going thru it.
Even on line on YouTube, there is some excellent videos of going thru it.
Stellar HDF Member
Joined: Sep 2013
Posts: 3,492
Likes: 610
From: USA
There is a Troubleshooting Guide on line. Go to HD's Service Info Portal and type "1998 wiring" in the search box at the top right of the screen. You don't even have to enter your VIN
https://serviceinfo.harley-davidson....cle/lookupForm
At the top of the results list will be " Wiring Diagrams & Electrical Troubleshooting Guide - 1998 All Models " . It has a section on the fuel injection the might be of interest to you.
https://serviceinfo.harley-davidson....cle/lookupForm
At the top of the results list will be " Wiring Diagrams & Electrical Troubleshooting Guide - 1998 All Models " . It has a section on the fuel injection the might be of interest to you.
Seasoned HDF Member
Joined: Feb 2007
Posts: 6,086
Likes: 1,128
From:
Are there any MM injection guru's here? Ive got a 98 Road King with the MM injection and having a runability issue. Starts and runs fine initially, will rev as normal when twisting the throttle and will run for any given amount of time while parked. I purchased bike as a wreck. Replaced parts needed to run. Bike had a horrible stumble just off idle under a load. remove all tins for paint and pulled intake. Found seals on intake on incorrectly and fixed that issue. also replaced pressure line from tank. Cleaned intake and reinstalled. Received tins after paint and reassembled the tank with pump and new internal injection type rubber hoses. sealed with new gaskets. Got bike back together and purged the fuel system. Started the bike and stumble is gone. Rode bike down the street and ran great for the first half mile. Went through 4 gears pulling hard through all 4 at or above 3500. Turned around to head back, and bike wouldn't rev above 3-3500 without backfiring through intake and exhaust. As if its running out of fuel. Didn't have this issue prior to removing pump and filter. It did have the stumble but would pull through the RPM band. ANY insight would be greatly appreciated.
How are the external fuel lines? They leak at the swivel after about 10 years and sometimes decompose from inside to outside.
Goodridge makes a good fuel line replacement model HDFL005 (2 lines included in package)that is cheaper and better than Harley.
You received a lot of good verified and common information regarding the M & M.
Have you checked the crank position sensor connector. NOT the sensor but the CONNECTOR.
It is the black pencil thick push-in & turn connector on the wire that goes from CRANK sensor by oil filter to computer.
The connector is located on the wire maybe 12 inches before the computer.
It on the throttle side of bike,behind painted side cover located by by the seat.
If you removed tins then it is highly likely that connector was disconnected.
Even if it looks visually connected it can be loose because the twist lock is not secure
Find that connector, clean it with contact cleaner and then zip tie it to itself and then zip tie to frame twice.
When loose the bike can momentarily turn off over bumps.
It might also run like someone is turning bike on and off rapidly.
Check it and let us know how it goes.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,081
Likes: 2,159
From: Ohio
The pipe plug in the bottom of the fuel line is the pressure port to check fuel pressure, it is a odd 1/16" size but Parker makes a brass fitting that goes 1/16" pipe to 1/8" plastic and can get a fuel pressure gauge in the system too know if you have a fuel problem, no guessing.
Engine temperature sensor is known to fail and can take fuel away to a lean condition, it is the heart of fuel control in this primitive EFI.
Engine temperature sensor is known to fail and can take fuel away to a lean condition, it is the heart of fuel control in this primitive EFI.
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Seasoned HDF Member
Joined: Oct 2007
Posts: 8,852
Likes: 2,494
From: Decatur, Alabama
Do a search for how to retrieve trouble codes out of the MMI FI system. It's been posted all over here. When you find the procedure, see what codes you may have stored, if any. I'm guessing by what you posted, your engine temp sensor needs to be replaced (that's code 14). It's the most common item to need replacing in the FI system. Cost is roughly $100. You DON"T have to pull the tank and lines to get the sensor out of the head like the service manual says. Remove the tank bolts, push forward a little, then lift the crossover tube up and over the coil. Now push the tank back and up as far as it will go. Hold in place with block of wood, shoe, rags, whatever. The rest is easy.
My bike eats a sensor about once every 20k. I keep a spare in the shop. However; don't just run out and buy one, see if the code is present. If not, look elsewhere.
carl
My bike eats a sensor about once every 20k. I keep a spare in the shop. However; don't just run out and buy one, see if the code is present. If not, look elsewhere.
carl
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Thread Starter
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1st Gear
Joined: Feb 2018
Posts: 5
Likes: 1
From: Texas
Update
Thanks to all for the replies... did find the problem... actually multiple problems.. !st.. fuel filter almost totally plugged.. 2nd... Regulator not working properly. Bike is now up and running well. Thanks again everyone!!
