CREDEATION
New Member
Hey,Have not checked fuel pressure,but will. I have taken tank off and checked for debris,by draining all gas out,it was clean.
Thanks,Credeation
Thanks,Credeation
Engine Dies And Runs In Spurts
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RibEye
Senior Member
If the issue is intermittent, and fuel pressure tests seem OK, whenever performed, The issue could also be the fuel pressure regulator. Under certain conditions, particuarly if fuel has been allowed to varnish a bit (sitting for more than a couple months), the fuel pressure regulator can become sticky. The symptoms are identical to the holes in the lines, except that they can be intermittent, showing up when taking off after idle or increasing from a steady speed. Holes in the lines do not tend to be intermittent, except that the symptoms may vary from submerged to emerged holes. So, that can help in distinguishing cause.
The fuel pump is single speed, and runs all the time the engine is running. The regulator should keep fuel rail pressure stable at around 58psi (+/- a couple lbs), regardless of load and rpm. When pressure increases past that point, because of lower demand, a spring-loaded diaphram in the regulator proportionally pushes open, bypassing the excess fuel back into the tank. When idling, the demand is the lowest, so the bypass is the greatest. If pressure drops, due to increased load/demand, but the bypass sticks at the higher bypass position, the fuel rail pressure drops, resulting in stuttering,, misfiring, flat power, etc., as descibed in above posts. Early on, the sticking can be brief, as the spring load in the regulator, combined with vibration can cause the regulator diaphram to unstick more or less quickly, resulting in brief sputtering when starting off from a stop, or right at an increase in demand (load/rpm).
Sticky pressure regulators will not throw codes on open loop engines (no O2 sensors), and may cause confusing codes on closed loop ones. With no codes to guide you, and many possible causes for the same symptoms, isolation can be difficult. The indicative symptom, for a regulator just starting to become sticky, is the brief stutter when starting off from stop, or right when increasing speed from a steady one. As the stickiness worsens the stuttering can become prolonged, even continuing for the rest of a ride session, only to clear up before you start her up next time, coming back in a few miles, etc.
This problem can masquerade as a thermal one, because of the enrichment that occurs when you first start up. When enrichment tapers out, the subtle leaning out from lowered fuel rail pressure tapers in. Also, the stuck regulator can pop back in normal operation, if you shut down for a few minutes, only to restick after a bit of time on the road.
I hope this helps. It was hard learned, over around 18 months of trying to track down the culprit, in my case.:newsmile093: Dealers, indy's, nobody could make it go a away. Let's just say, there is nothing in fuel, air, or spark delivery that I am afraid to work on. I know every related wire, bolt, and connector on my scooter, personally.
Enjoy,
Rich P
The fuel pump is single speed, and runs all the time the engine is running. The regulator should keep fuel rail pressure stable at around 58psi (+/- a couple lbs), regardless of load and rpm. When pressure increases past that point, because of lower demand, a spring-loaded diaphram in the regulator proportionally pushes open, bypassing the excess fuel back into the tank. When idling, the demand is the lowest, so the bypass is the greatest. If pressure drops, due to increased load/demand, but the bypass sticks at the higher bypass position, the fuel rail pressure drops, resulting in stuttering,, misfiring, flat power, etc., as descibed in above posts. Early on, the sticking can be brief, as the spring load in the regulator, combined with vibration can cause the regulator diaphram to unstick more or less quickly, resulting in brief sputtering when starting off from a stop, or right at an increase in demand (load/rpm).
Sticky pressure regulators will not throw codes on open loop engines (no O2 sensors), and may cause confusing codes on closed loop ones. With no codes to guide you, and many possible causes for the same symptoms, isolation can be difficult. The indicative symptom, for a regulator just starting to become sticky, is the brief stutter when starting off from stop, or right when increasing speed from a steady one. As the stickiness worsens the stuttering can become prolonged, even continuing for the rest of a ride session, only to clear up before you start her up next time, coming back in a few miles, etc.
This problem can masquerade as a thermal one, because of the enrichment that occurs when you first start up. When enrichment tapers out, the subtle leaning out from lowered fuel rail pressure tapers in. Also, the stuck regulator can pop back in normal operation, if you shut down for a few minutes, only to restick after a bit of time on the road.
I hope this helps. It was hard learned, over around 18 months of trying to track down the culprit, in my case.:newsmile093: Dealers, indy's, nobody could make it go a away. Let's just say, there is nothing in fuel, air, or spark delivery that I am afraid to work on. I know every related wire, bolt, and connector on my scooter, personally.
Enjoy,
Rich P
kansaskid72
Member
RibEye, thanks! I'm having the stutter/hesitation randomly occur and this may be it. Many posts on the net say to listen for gas spraying in the tank when you prime the pump. But...if you prime it over and over there is already pressure in the lines and the regulator bypasses all that prime shot back into the tank. So you can't rely on just listening for spraying fuel when you hit the run switch, you have to look at the hose to see the spray, or check the spray is coming from the end of the filter housing (in my case with an '07 FXDB). Am I right?
After the system primes, the pump shuts off until the demand is there for more fuel. If you just crank the engine without it starting, the pressure in the fuel system will drop and it will usually prime again. You should hear and see movement in the fuel in the tank if the fuel level is lower than 1/2 tank.
kansaskid72
Your problem could be related to low fuel pressure to and not necessarily an internal leak.
kansaskid72
Your problem could be related to low fuel pressure to and not necessarily an internal leak.
fxstsiharelyo5
New Member
Im doing this next , hav that weird idle, replaced the IAC helped some but I have that sinking feeling this is what it is. I hear like a gasing and a bubbling,
the bubbling could be simply the tank equalizing from being on the stand and picked straight up, Ill check this - easy but the gasing is giving me the funny feeling.
Hey guys---been having prolems when starting my 2003 fatboy,it does start after a few attempts and seems to run well after,----but i have noticed the hissing and bubbling sound inside the fuel tank, so having read this thread i think the problem is the fuel hose cheers Gazman
ol55forever
Member
Is there anything to replacing the long hose that goes to where the disconnect is like gaskets and such? I have replaced filter and still have the problem of sputtering on accelleration. Pressure is 60# and steady. The shop said to remove the TFI, which I did and still have the issue. Thanks for any and all info.
mikeforcec51
Member
I'm working on a 1999 flhtcui and i'm haveing issues with the fuel injection system. When i turn on the key i hear no primeing of the fuel pump. It won't fire up when i try to start it. I check all the fuse's on both sides of the covers on the bike and all fuses seem to be working correctly. It won't start so i sprayed some fluid into the throat of the intake and it started only for a second and then died. Can anyone tell me what part entergizes the fuel pump to prime.
Second issue. When the motorcycle was working and starting fine when you first started it it ran fine , untill the engine was warming up then it would start to spit, spudder, and make the spark plugs turn rich black. Why is the fuel injection causing these issues.
Can anyone help me.
Second issue. When the motorcycle was working and starting fine when you first started it it ran fine , untill the engine was warming up then it would start to spit, spudder, and make the spark plugs turn rich black. Why is the fuel injection causing these issues.
Can anyone help me.