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Runs rough when hot

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Old Sep 29th, 2012, 02:20 AM     #1
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Runs rough when hot

Hi all, first, I have an 08 Heritage Softail Classic with basic stage 1 with Dobec Gen3. Normally runs GREAT. Last summer I was in Seaside Or and she got really hot and started running rough and was hard to keep running at an idle. I figured I had some bad gas, parked her and a few hours later, she started up fine and ran great until she got hot and then it was sputtering and on a hard throttle it would sputter and miss, but if I rolled the throttle gently, she would nurse up to speed fine. I spoke to a Harley tech in Portland(??) via phone who agreed it was probably bad gas. that was about when I learned of the fuel line issues my year had (not from the tech). I have not yet pulled it apart to replace so this could be an underlying problem.

Any ho, this year I ran really hot again leaving Anacortes (OysterRun) and she did the same thing, got really rough idling, a few (pre-cumbustion pings??) and at a few points when I would accellerate from a stop, it sounded like one cylinder was shut down, almost like a lawn mower engine sound for a few hundered feet then would jump back to normal. I checked the plugs at hotel and they looked as if she was running lean. I called Dobeck and Matt told me it would be OK to dial up my green one point which I did, I also dialed up my red .5 to cover my hard accelleration. This seemed to pretty much help me out to get home but she still doesnt like to hard accellerate, she just coughs and gurgles...What should I look for? Oh yeah, I am a noob wrencher here so still learning. thanks in advance.
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Old Sep 29th, 2012, 02:46 AM     #2
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Re: Runs rough when hot

Start with fuel rail pressure test. Your symptoms are classic for pin holes in the "inside the tank" fuel lines. Running better when cold could be due to the normal enrichment during warm-up. Running lean on both cylinders is another indicator for the need to check for this.

One more thing to check: bad crimp to an injector connector, or an inside the insulation wire break. While cold, the insulation could be stiff enough to keep the connection lined up. Once hot, the insulation will tend to become more flexible, allowing the connection to become more intermittent.

Neither issue will generally throw a code, as long as oxygen sensors are bypassed. The injector wire issue will throw a code, but the bad connection has to become pretty bad before a code will be thrown.

Good luck,
Rich P
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Old Sep 29th, 2012, 02:16 PM     #3
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Re: Runs rough when hot

Harley Davidson Community (Engine Dies And Runs In Spurts) Have a look here and what Ribeye posted sounds like a good place to start as well
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Old Sep 29th, 2012, 06:02 PM     #4
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Re: Runs rough when hot

Thanks...my gut is telling me its the pin hole in the fuel line that is causing this as it is mostly consistent with what I read about it, what was fooling me is it is not a constant...almost finished with our house re-model, and clutch in my truck is getting replaced, will tackle this soon...lol.
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Old Sep 29th, 2012, 09:01 PM     #5
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Re: Runs rough when hot

Just pulled the Fuel Pump fuse (15a) and tried to start her up per directions...bingo, no start up. Anyone know off hand the part number I need to order? lol
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Old Sep 29th, 2012, 11:36 PM     #6
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Lightbulb Re: Runs rough when hot

I don't get the disconnect of the fuse , then start up?

What is it you are trying to do... IF the fuse is Pulled It won't start.

What am I missing here? ???

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IF any thought was toward the Gen3, Unhook the ground wire on the gen3 and it reverts TOTALLY back to HD's settings. Just to see IF it runs the same...

The heat sensor could be bad OR not making proper contact and causing this Missing...

Where is Hoople??? We need Hoople. I'll send a PM to arouse him

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Old Sep 30th, 2012, 12:09 AM     #7
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Re: Runs rough when hot

I don't get the disconnect the fuse and start up thing either.

If there is a pin hole in the fuel pick up line, the bike will usually run normally when the tank is full and once the fuel level drops below the pinhole the pump starts pulling in air with the fuel; that's when the missing starts. At that point you can open the tank and you can hear the hissing. Engine temperature doesn't have anything to do with the pinhole problem.

I would go back and read Rib Eye's post and start there. I would also take the Dobeck unit out of the picture as Bubbie suggested and see how she runs on the factory fuel settings.
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Old Sep 30th, 2012, 01:02 AM     #8
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Re: Runs rough when hot

but wondering if this was a test where the ‘system’ was allowed to prime, as for normal start up, then the fuse pulled when pressurized. If holes in hose then pressure would leak off quickly and not start, but if hose is good, engine would at least start (I would think) then sputter and quit. If no start as in this case, I’d pull the pump and visually inspect before ordering parts.

Quote: Originally Posted by Jack Klarich View Post
Harley Davidson Community (Engine Dies And Runs In Spurts) Have a look here and what Ribeye posted sounds like a good place to start as well
Seems Post 21 in link given by Jack has part numbers. Or consider high pressure submersible reinforced fuel injector hose from an auto parts store as per TQ1's idea. That link and all posts above are tremendous!
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Old Sep 30th, 2012, 02:25 AM     #9
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Re: Runs rough when hot

Quote: Originally Posted by dolt View Post
I don't get the disconnect the fuse and start up thing either.

If there is a pin hole in the fuel pick up line, the bike will usually run normally when the tank is full and once the fuel level drops below the pinhole the pump starts pulling in air with the fuel; that's when the missing starts. At that point you can open the tank and you can hear the hissing. Engine temperature doesn't have anything to do with the pinhole problem.

I would go back and read Rib Eye's post and start there. I would also take the Dobeck unit out of the picture as Bubbie suggested and see how she runs on the factory fuel settings.
Quote: Originally Posted by PigSnot View Post
but wondering if this was a test where the ‘system’ was allowed to prime, as for normal start up, then the fuse pulled when pressurized. If holes in hose then pressure would leak off quickly and not start, but if hose is good, engine would at least start (I would think) then sputter and quit. If no start as in this case, I’d pull the pump and visually inspect before ordering parts.



Seems Post 21 in link given by Jack has part numbers. Or consider high pressure submersible reinforced fuel injector hose from an auto parts store as per TQ1's idea. That link and all posts above are tremendous!
The system is turned on and allowed to prime (the fuel rail is brought up to pressure). This is what is happening when you first get ready to hit the starter, where you hear the pump run a bit and shut off. If you get it to prime in this way, then pull the pump fuse, if the line holds pressure then when you hit the starter, she will fire and run briefly, from the stored pressure. If the pressure bleeds off through a hole in the lines, she will not fire and run even briefly.

Injectors require a set fuel rail pressure to function. They do not suck fuel, so no air can be sucked in though a pinhole. The fuel llines are positively pressurized. Air can't get in thought the hole. However, if fuel rail pressure is insufficient, you will not have what is needed to push the fuel out the atomizing injectors, hence, the stuttering and mis-firing.

Fuel pressure is regulated, post-pump, by a bypase valve, which simply bypasses excess pressure from the single-speed pump, back into the tank. This will compensate for pressure loss through a hole, but only up to a certain point, that is dependent upon teh size of the pressure leak.

I seem to recall that fuel rail pressure is regulated at somewhere in the neighborhood of 55 psi. If pressure is lower, less fuel is pushed through open injectors and your mix will wind up lean, for any injector "on-time". If lean enough, stuttering and mis-firing ensues. This results in running decently at lower demands, but crapping out when engine needs more fuel than the faulted system can provide...stuttering.

Soemtines you see engine appearing to run OK until the fuel level in teh tank drops below where the hole in the line is. This is because fuel in front of a hole provides just a bit of resistance to the pressure leak. On borderline systems, it might be enough to allow the engine to run. Just know that this is very temporary, and will get worse until fueld level makes no difference. Also note that you are running lean, even though you don't notice it. Fuel pressure is still leaking away, jnust a bit less than when the problem comes to your awareness.

The cool part is that your HD is really trying to run for you, automatically trying to compensate for issues like this. Just know she can only do this so far, then, that's it and she stutters.

I hope this helps...

Good luck,
Rich P
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Old Sep 30th, 2012, 10:39 PM     #10
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Re: Runs rough when hot

Quote: Originally Posted by RibEye View Post
The system is turned on and allowed to prime (the fuel rail is brought up to pressure). This is what is happening when you first get ready to hit the starter, where you hear the pump run a bit and shut off. If you get it to prime in this way, then pull the pump fuse, if the line holds pressure then when you hit the starter, she will fire and run briefly, from the stored pressure. If the pressure bleeds off through a hole in the lines, she will not fire and run even briefly.

Injectors require a set fuel rail pressure to function. They do not suck fuel, so no air can be sucked in though a pinhole. The fuel llines are positively pressurized. Air can't get in thought the hole. However, if fuel rail pressure is insufficient, you will not have what is needed to push the fuel out the atomizing injectors, hence, the stuttering and mis-firing.

Fuel pressure is regulated, post-pump, by a bypase valve, which simply bypasses excess pressure from the single-speed pump, back into the tank. This will compensate for pressure loss through a hole, but only up to a certain point, that is dependent upon teh size of the pressure leak.

I seem to recall that fuel rail pressure is regulated at somewhere in the neighborhood of 55 psi. If pressure is lower, less fuel is pushed through open injectors and your mix will wind up lean, for any injector "on-time". If lean enough, stuttering and mis-firing ensues. This results in running decently at lower demands, but crapping out when engine needs more fuel than the faulted system can provide...stuttering.

Soemtines you see engine appearing to run OK until the fuel level in teh tank drops below where the hole in the line is. This is because fuel in front of a hole provides just a bit of resistance to the pressure leak. On borderline systems, it might be enough to allow the engine to run. Just know that this is very temporary, and will get worse until fueld level makes no difference. Also note that you are running lean, even though you don't notice it. Fuel pressure is still leaking away, jnust a bit less than when the problem comes to your awareness.

The cool part is that your HD is really trying to run for you, automatically trying to compensate for issues like this. Just know she can only do this so far, then, that's it and she stutters.

I hope this helps...

Good luck,
Rich P

Very big help. I am more than likely going to change to a Gates brand submersible fuel line hose (5/16 id) and not even bother trying to find the HD replacement line. Today is Sunday so no luck at any of my local parts places as they are closed. May require a 70 mile trip to Port Angeles to NAPA.

right now my hang up is my noobness. I have the console off and the fuel pump plate cover unscrewed, but getting the assembly out is proving to be a bit daunting. All the components are plastic and if I bung it up, seems to be costly to fix...I am reading the HD shop bible, and it is kind of vague on how to manipulate the assembly out. Any advice would be appreciated.

One question, My tank level is well below half tank, how important is it to drain the tank (no open heat sources or flame) before I gently remove the assembly and replace lines??
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