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FJR Motorcycle Forums
Technical & Mechanical Problems
Engine only runs with vacuum line disconnected
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<blockquote data-quote="road runner" data-source="post: 1447351" data-attributes="member: 5116"><p>If it starts and runs after unplugging the MAP and plugging the Vacuum line, then that tells me the MAP is working. Because you plugged the line you are not introducing air and leaning it out. When the MAP has no vacuum it tells the ECM max load or WOT so the ECM richens things up by keeping injectors open longer. If you did this test and nothing was different then I would say the MAP may be bad, but because is richens it up and then starts and runs that means it is working as designed. Also a good idea to check all vacuum lines for leaks or plugs, but from what you said the engine did when you removed and or plugged them up, it sounds like they are all working.</p><p></p><p>Now you have to figure out why it needs to be richened up so much to start and run. Like others said I would go to diag. screen to see what the ECM is seeing from all the sensors. Clear fault codes and see if any come back. The code in it may be an old code. Also Need to check fuel pressure. Low pressure will make it lean. A leaking injector will make one cylinder too rich but other 3 cylinders lean. Put a pressure gage on it, key up and make sure pressure is good, key off and make sure it stays for long time. If pressure drops off right away that says leaking injector.</p></blockquote><p></p>
[QUOTE="road runner, post: 1447351, member: 5116"] If it starts and runs after unplugging the MAP and plugging the Vacuum line, then that tells me the MAP is working. Because you plugged the line you are not introducing air and leaning it out. When the MAP has no vacuum it tells the ECM max load or WOT so the ECM richens things up by keeping injectors open longer. If you did this test and nothing was different then I would say the MAP may be bad, but because is richens it up and then starts and runs that means it is working as designed. Also a good idea to check all vacuum lines for leaks or plugs, but from what you said the engine did when you removed and or plugged them up, it sounds like they are all working. Now you have to figure out why it needs to be richened up so much to start and run. Like others said I would go to diag. screen to see what the ECM is seeing from all the sensors. Clear fault codes and see if any come back. The code in it may be an old code. Also Need to check fuel pressure. Low pressure will make it lean. A leaking injector will make one cylinder too rich but other 3 cylinders lean. Put a pressure gage on it, key up and make sure pressure is good, key off and make sure it stays for long time. If pressure drops off right away that says leaking injector. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Engine only runs with vacuum line disconnected
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