G oog le Buell 1125R Forum | Login/out | Topics | Search | Custodians | Register | Edit Profile


Buell Forum » 1125R Superbike Board » Erratic fuel pressure and fuel voltage « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Sunday, June 17, 2018 - 09:55 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Newbie. Bought a 2009 1125CR with a supposed fuel pump problem. Bike would run, but would cut out, hard, under load. Fuel pressure in diagnostic mode was reading anywhere from 100 kPa to 500 kPa rapidly, so fast it was hard to get an accurate reading. Had typical fuel error codes. Also had an auxiliary circuit error. All my testing lead to a bad ECM as it could not detect the aux. circuit, as the electrical troubleshooting flow chart stated. Bought an Ebay ECM, that fixed the aux. circuit and improved the rough running, but still feel the erratic surging under load. But at least it was rideable. Still the fuel pressure and fuel voltage are all over the place. Suspected the fuel pressure sensor; replaced it with new factory one from St. Paul Harley; nothing changed. Suspected Fuel pump and/or regulator; bought an Ebay one (i know, i know, Ebay), and replaced the entire fuel pump assembly with the used Ebay one. Same issue. I have doubts about 2 different pump assemblies having the same issue, but coincidence? Anyways any advice from any one? I have yet to ride it except on test runs, as I do not trust it fully. Any help greatly appreciated. If you type in erratic buell 1125r fuel pressure on youtube, there is a person who posted a video of the exact fuel pressure readout on his/her instrument cluster. States in the description that they replaced the pump with a chinese unit, had this problem, then replaced with a OEM one, and problem went away. Out of options, I dont want to buy a new $255 pump from ST. Paul and have the exact same issue that did not get fixed. With all these issues, I suspect that the previous owner put an XB battery in it an fried stuff, like some of the others posts stated. Another funky issue this bike has is the Instrument cluster has a pulsing draw on the battery with the key off. I even turn the kill switch off as stated in the archives, but to no avail.
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Sunday, June 17, 2018 - 12:57 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

To add to this, I have looked for any diodes that might have been fried, but cannot find any that would be associated with the fuel pump circuit. Is the fuel pump regulator a mechanical type, or is it electrical? Could my Ebay ECU have the exact same issues as my stock one? I am at the point where I am going to replace the ECU with a brand new one from IDS or replace the fuel pump assembly with a brand new one from ST. Paul Harley. Any other things I could check?
Top of pagePrevious messageNext messageBottom of page Link to this message

Nuts4mc
Posted on Sunday, June 17, 2018 - 02:05 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

It appears the wiring inside the epoxy "bulkhead/feed through" fuel pump connector can go bad...here's an old post:
http://www.badweatherbikers.com/buell/messages/290 431/760318.html?1431529294

since you're new at this ...use the google search at the top of this page...it looks only at the 1125 forum and you can learn alot with only a few key strokes...

might also check the big grey connector that connects the stator to the rest of the electrical system ( under the seat with 10ga yellow wires)...it is a very "weak" design

(Message edited by nuts4mc on June 17, 2018)
Top of pagePrevious messageNext messageBottom of page Link to this message

Stevel
Posted on Sunday, June 17, 2018 - 03:11 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

You are not troubleshooting correctly nor was any of your predecessors. This is always expensive. You end up blaming everyone else but yourself because you don't know any better. Don't feel bad about this, read these threads and you will find many others do the same thing. The solution is of course to understand what should happen and then find out what is happening.

So, to do the former, you must hook up a mechanical fuel pressure gauge. Then you have to look at the fuel pump input with a oscilloscope. The fuel pump is driven with pulse width modulation. (PWM) (Duty cycle control) This is how the ECM controls pump motor speed and fuel pressure. You can then compare what the fuel pressure sensor is seeing and how the ECM is interpreting it. All things will become clear.

You will soon discovery that you have no way to hook up a pressure gauge and more disturbing is that none of the dealers do either. So, not only are you chasing your ass, so are all the dealers.

I have commented about this multiple times in previous threads. Even mentioning the source of the appropriate adaptors required for the fuel gauge. This issue is everywhere in the automotive/motorcycle arena. Mechanics are not trained in electronics nor are they computer types in possession of ECM source code and even if they were, they wouldn't know how to read it. So when the built in diagnostics tell lies, only basic troubleshooting techniques will work. Good luck.
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Sunday, June 17, 2018 - 05:49 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Nuts4mc - thanks for the response. What I have also failed to mention is that I have searched every fuel pump error thread in this website for over 2 months now, and have researched all of those possibilities, but to no avail. Thus the reason I posted hoping to maybe get newer info.

Stevel - thanks for the reply, but does not help with my issue.
Top of pagePrevious messageNext messageBottom of page Link to this message

Willmrx
Posted on Sunday, June 17, 2018 - 06:36 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Fuel injectors, clogged or dirty?
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Sunday, June 17, 2018 - 09:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Willmrx - I was thinking that as well, but would it cause the pump pressure and pump voltage to fluctuate so bad? Just for a safe bet, I should just go have them ultrasonic cleaned and flow tested. Fuel injection shop here does it for $50 a pair. It would be a reassurance at best.
Top of pagePrevious messageNext messageBottom of page Link to this message

Stevel
Posted on Monday, June 18, 2018 - 02:00 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

My point is simple, unless you know what the problem is, any corrective action may not only be wrong and expensive shot gunning parts, but harmful. Hooking up a mechanical fuel pressure gauge as an extension to the fuel pressure sensor is not expensive.
Top of pagePrevious messageNext messageBottom of page Link to this message

Nuts4mc
Posted on Monday, June 18, 2018 - 07:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

KISS principle...have you tried riding/running the bike with the gas cap open...maybe your tank is not venting and the pump just can't pump against the vacuum,then somehow it leaks some atmosphere in and the pump regains it strength...the "vent" on these things is usually tooo good as many of us out here in the hot southwest don't dare park the bike in the garage until it's done "out gassing" and cools off...the only other thing(s) I could think of is a bad crank position sensor ( the sensor is mounted in a "dirty" place and wiring/connections could be affected) the ECM doesn't know where the crank is at..or the the throttle position sensor is all screwed up and sending the ECM some bad info as to where the butterfly valves are... Steve has a good point tho .. a simple mechanical gauge might give you some info to validate the info you're seeing on the display ...hth
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Monday, June 18, 2018 - 08:19 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

*Update* Reading more of the archive posts, I saw a post regarding the fuel system and someone making a comment of running the bike with the fuel pressure switch/sensor unplugged. So, I did just that, even though the switch is a new dealer one. And boom, the bike runs like it should! No hesitation, no surging, idling better and more consistent, albeit as good as these can run at idle. Drove it a good ten minutes, and put it through its paces. Flawless! So, with that being said, do I have a bad sensor from the manufacturer, or what? Or is there some other problem at hand here? I will continue through the archives and see what else I find, but at least I have limited it down to a possible culprit or assistant to the culprit.

(Message edited by Trendkillkustoms on June 18, 2018)
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Monday, June 18, 2018 - 09:40 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

*Update 2* I did the trouble shooting for the fuel pressure sensor per the electrical manual, 6-67. Everything checked out fine and it says replace the fuel pressure sensor. Being that this one was brand new, was it DOA? Thoughts?
Top of pagePrevious messageNext messageBottom of page Link to this message

Two_seasons
Posted on Tuesday, June 19, 2018 - 06:36 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Possible short in that part of the harness. Pulling connector cleared the short,
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Tuesday, June 26, 2018 - 07:36 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Late post, been busy. I have replaced the fuel pressure sensor with yet another genuine HD one, still the problem persists, erratic pressure and erratic pump voltage to match. And the bike responds to this as well, falls flat on its face,since the pump pressure is told to drop damn near to >100 kPa while at full throttle for a millisecond.
I am suspecting the ECM as there seems to be no other device that is in that circuit that could be causing the massive fluctuating pressure deviation. Can anyone else recommend something that I might be missing?
Top of pagePrevious messageNext messageBottom of page Link to this message

Fresnobuell
Posted on Tuesday, June 26, 2018 - 07:14 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

You replaced the ECM already? You think the second one is bad as well?
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Wednesday, June 27, 2018 - 08:44 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Fresno, I have had some more insight into my issue, and so I have some other things to now check that could affect the sensor input/output. Before that, yes, I had suspected the other to have issues. I think this because of how sensitive the ECM's are to over current and reverse polarity. Reading the posts, I have seen where replacing a battery and putting in an XB battery is too easy if one does not look out for it and its sounds like the ECM's take a hard hit when this happens. Not being the original owner, who knows what anyone has possibly done to the Buell before me.

(Message edited by Trendkillkustoms on June 27, 2018)
Top of pagePrevious messageNext messageBottom of page Link to this message

Fresnobuell
Posted on Thursday, June 28, 2018 - 04:40 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

What is an XB battery? And why would this cause an issue?
Top of pagePrevious messageNext messageBottom of page Link to this message

Trendkillkustoms
Posted on Thursday, July 05, 2018 - 07:49 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

XB, as in Buell XB12S, etc. If I am not mistaken, the Buell XB batteries where the same dimensionally, but the posts where reversed from the 1125's. Thus if not checked, and you hook it up and turn the key, you have just sent angry pixies the wrong way (reverse polarity) and possible damage could occur.
After working with Tim at IDS, we found that the culprit was a burned out flyback diode on not one but both of the fuel pump assemblies. Took quite a while to locate, but that was what did it, and they have now archived this in their system. The fuel pump output signal to the ECM was being spiked with voltage and causing inaccurate signals to the ecm. Thanks to all who helped. Tim is was instrumental in helping me with this problem and I highly recommend him for electrical issues on the Buell motorcycles.
Top of pagePrevious messageNext messageBottom of page Link to this message

Stevel
Posted on Friday, July 06, 2018 - 03:02 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I understand the use of flyback diodes. For those unfamiliar with the practice, the reason for their use stems from the use of inductive loads where current leads voltage at application because the magnetic field around the wire must first be built before current can pass to the output side of the wire. However, when the load is shut off, this same magnetic field collapses back into the wire opposite in polarity and at twice the charging voltage. This reverse voltage can damage solid state electronics, so shunting diodes are used to dump this energy to ground protecting the electronic devices. These back EMF pulses are short in duration and these flyback diodes are not designed for reversed battery connections and will quickly fail. Normally, they will be mounted at the inductive device. So, my question is where are they physically? I can't remember ever seeing any.
« Previous Next »

Add Your Message Here
Post:
Bold text Italics Underline Create a hyperlink Insert a clipart image

Username: Posting Information:
This is a public posting area. Enter your username and password if you have an account. Otherwise, enter your full name as your username and leave the password blank. Your e-mail address is optional.
Password:
E-mail:
Options: Post as "Anonymous" (Valid reason required. Abusers will be exposed. If unsure, ask.)
Enable HTML code in message
Automatically activate URLs in message
Action:

Topics | Last Day | Tree View | Search | User List | Help/Instructions | Rules | Program Credits Administration