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Panshovevo
Posted on Sunday, July 26, 2015 - 03:16 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Hi all, been distracted with low back problems, haven't been on the board in a while.

Ran out of fuel last Sunday with no warning light. Started using a trip meter to keep track.

This week, rode it a couple of times, and the warning light is coming on with plenty of fuel in the tank, staying on for a few miles, going off, then on and off sporadically.

Any thoughts?

Rode it last night, it just seemed unhappy overall on the way to dinner, then ran better on the way home.

Voltage levels seem fine.

At the last traffic light we stopped at, I thought I heard a sickly sounding car horn for a second, but the wife thought the noise came from the bike. She wasn't certain, and neither was I.

Don't know quite what to think...lots of rain around today, so I'm holed up in the shop working on the Shovelhead.

Edited to add I'm searching older threads as time permits. Cold temps are definitely NOT a factor.
Heat doesn't seem to be either, as it has happened in 95+ and 70 degrees.
No check engine light either, that I've seen.
(Message edited by Panshovevo on July 26, 2015)

(Message edited by Panshovevo on July 26, 2015)

(Message edited by Panshovevo on July 26, 2015)
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Shawns
Posted on Sunday, July 26, 2015 - 05:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thermistor on the pump. They are a known issue.
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Two_seasons
Posted on Sunday, July 26, 2015 - 08:20 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

May just need many engine starts to clear the light.

I've read it takes 50 engine starts to clear DTC's.
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Rogue_biker
Posted on Sunday, July 26, 2015 - 11:28 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The low fuel light sensor, or Thermistor on your bike has failed. It needs to be replaced.

The Thermistor is attached to the bike's fuel pump, which is located in the frame, directly above the swing arm.

To replace the Thermistor, you must remove the swing arm and drain the remaining fuel (both very easy to do). Then you can pull the fuel pump out, locate and replace the Thermistor (it's attached to the pump). American Sportbike sells new Thermistors designed for the Firebolt for $15 I believe. This part requires you to solder the ground wire to the Thermistor body for it to work properly.

It's not a tough job, in fact it's very easy provided you have a service manual, and have a front tire chock, and a scissor jack to raise the rear of the bike using the muffler.
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Zac4mac
Posted on Monday, July 27, 2015 - 12:14 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The "on and off sporadically" screams bad connection or broken wire.
...in addition to a likely bad thermistor.
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Nuts4mc
Posted on Monday, July 27, 2015 - 10:20 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

pictures in this thread:
http://www.badweatherbikers.com/buell/messages/290 431/728008.html?1391094574
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Panshovevo
Posted on Monday, July 27, 2015 - 11:36 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thanks for all the responses.

Brief update: not a lot of time to spend on it yet, but I checked for trouble codes this morning.
Although the check engine light wasn't staying on for 8 seconds after power-up like the manual says it will, it did have two historic codes stored.
U0001, comm error
P0087, low fuel pressure

I'm guessing running out of fuel would trigger P0087, not sure about the other, but will be checking all the connectors and grounds.
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Panshovevo
Posted on Monday, July 27, 2015 - 03:39 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Section 6.19 of the Electrical manual confirms that running out of fuel will set the P0087 DTC.
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Panshovevo
Posted on Friday, August 21, 2015 - 09:01 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Update: the bike has continued to run as well as it did when I bought it.
The low fuel warning light comes on when the coolant temp reaches 155 F, and goes off when it hits 173F. At night, in current ambient temps, the temp varies between 172 and 175, thus the on and off light.
I thought I understood this is due to the 6.1 firmware in the IC, but after rereading some old threads, it may be the thermistor.

The light stays off as long as the coolant temp stays above 173 F.

Fuel pressure with the motor not running will sometimes reach 400 KPA and stay there, other times it will vary between 40 and 150 KPA and set the trouble code again.

I removed the fuel pressure sensor yesterday to see if I could hook up a gauge in place of it, but haven't yet figured out what type of thread it is. Anyone know?

I did a search for fuel pressure sensors, and came up with identical looking units on EBay for Ford diesels, but as yet, don't know the pressure range they operate at. I may be able to get that info today.
(Yes, I know that diesels typically operate at much higher injector pressures, but without knowing at what point in the system they use the pressure sensor, upstream or downstream of the injection pump, it would be hard to guess whether it's a high pressure or medium pressure sensor.)
While playing with it, the high fuel pressure code came up. I assume the ECM is trying to compensate for the perceived low fuel pressure by driving the pump faster.

The oddest thing is when the bike is started, the fuel pressure goes to where it should be and stays there. 410-420 KPA.

I'm checking all the electrical connections and grounds today.
I'll let you know what I find.

If anyone knows what thread the pressure sensor uses, I'd appreciate that info.

(Message edited by Panshovevo on August 21, 2015)

(Message edited by Panshovevo on August 21, 2015)
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Panshovevo
Posted on Friday, August 21, 2015 - 09:07 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Is it possible that the odd noise mentioned in the original post came from the fuel pump?

It only lasted for a second or so, and the pump has continued to work.

Edited to add I finally checked the resistance of the thermistor. It's 2.3 K ohms with the bike at ambient temp, around 90 degrees.

(Message edited by Panshovevo on August 21, 2015)
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Panshovevo
Posted on Friday, August 21, 2015 - 05:40 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Further food for thought...
Just for the hell of it, I stuck a probe in the fuel pump ground wire that goes to the ECM, turned on Diagnostic mode and grounded the probe for a second.
The pressure shot up to 550 KPA instantly.

That, combined with the Comm Error, has me suspecting the ECM ground. Next on the list.

Also wondering if maybe the Race ECM might operate the pump differently, when the engine isn't running.
As I said before, pressure is normal when it's running.
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Panshovevo
Posted on Friday, August 21, 2015 - 06:31 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Another odd thing I noticed...while watching fuel pressure in Diagnostic mode with the engine off, at one point the display was showing 40 KPA. I flipped the on/off switch a couple of times, and noticed a short grunt out of the pump and a surge of pressure every time the switch went off.

Still haven't got to the ECM ground to check it.
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Panshovevo
Posted on Friday, August 21, 2015 - 08:53 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Still haven't found the ECM ground.

I did use the diagnostic flow chart for the comm error...bad IC, according to those tests.

The Electrical manual has a picture that purports to show the ECM ground on the left side of the motor, but the side of my motor doesn't look like the one in the picture, unless I'm totally confused as to what it's showing.
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