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1stSSPZ
Joined: 11 Apr 2016 Posts: 4 Location: Lubbock, Texas
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Posted: Sat Dec 19, 2020 6:26 pm Post subject: Fueling issues-94 K1100rs |
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Greetings all! My first post on this wonderful forum after spending hours thumbing thru all the posts. Wonderful info! I am afraid I am stumped by a problem and need advice.
1994 K1100rs, 72K miles or so. Over the last year or so I have been plagued by an intermittent loss of power while riding, something akin to hit the kill switch off and on. About a month ago, removed the tank to replace the air filter and replace a cracked fuel delivery hose.
On my first test ride, key on, fuel pump energizes. Can also hear a mild splashing sound of fuel running back into the tank from the return line, which was a first. Ran great for about 5 miles, then seemed to run out of fuel and die (approx half tank of fuel). Would try to fire but, no-go.
Wife came with truck/trailer after about 15 minutes, bike fired right up and rode it into the trailer. Now, in the garage I have removed the fuel cap assembly. Bike will start easily, all the time with fuel running back into the tank from the return hose. Not a big stream but I suppose you could call it a serious dribble. Shut the bike off but will not restart for an hour or so, then cranks right off. Fuel pressure regulator? Fuel pump? Thanks for your replies. _________________ 1985 K100rs, 94 K1100rs, 98 K1200rs, 01R1150gs |
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Flying Duck PsyKotic Waterfowl
Joined: 27 Jan 2005 Posts: 10085 Location: Bumf***, WA
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Posted: Sat Dec 19, 2020 7:16 pm Post subject: |
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The first suspect is the fuel tank electrical connector. Try moving that around to see if it causes intermittent running.
And while you're at it, it's a good idea to replace the fuel filter - NAPA 3032 is what I use. _________________ 93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE |
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Grunter Flying Brick Rider
Joined: 30 Sep 2015 Posts: 368 Location: North East England
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Posted: Sun Dec 20, 2020 7:18 am Post subject: Fuel tank connector |
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I had a similar problem with the connector that I attempted to cure by fitting an after market 4 pin multi-connector. That too proved unreliable, so I removed the new items and hard wired both ends of the cable into a miniature 4 point connector bar. That has proved totally reliable. If I have to remove the tank, I can simply unscrew one side of the connector bar and pull the wires free. They are colour coded so no chance of mixing them up.
The copper ends of the cables on both sides were soldered to give them strength so they were not crushed by the connector screws.
I have done the same to both of my K75 bikes. A simple and cheap alternative _________________ 1997 K1100LT
1994 R1100RS |
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1stSSPZ
Joined: 11 Apr 2016 Posts: 4 Location: Lubbock, Texas
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Posted: Sun Dec 20, 2020 8:28 am Post subject: |
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Thanks for both replies, I think the faulty connector would certainly address the issue of the intermittent loss of power. Do you think that would also cause the issue of the fuel constantly being pumped back in to the tank from the return line? I pulled the cap assembly of off my 98 K1200rs and that does not happen on that bike. Thanks! _________________ 1985 K100rs, 94 K1100rs, 98 K1200rs, 01R1150gs |
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flybd5 Flying Brick Rider
Joined: 01 Jul 2019 Posts: 371 Location: Massachusetts, USA
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Posted: Sun Dec 20, 2020 12:14 pm Post subject: |
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1stSSPZ wrote: | Thanks for both replies, I think the faulty connector would certainly address the issue of the intermittent loss of power. Do you think that would also cause the issue of the fuel constantly being pumped back in to the tank from the return line? I pulled the cap assembly of off my 98 K1200rs and that does not happen on that bike. Thanks! |
Isn't that why they call it a "return line"? Fuel injection systems generally send more fuel to the injectors than the injectors can use in order to maintain a constant, consistent supply of fuel to the engine. I once disassembled a small French turbine engine that operates exactly the same way, but with a mechanical fuel pump, not electric. _________________ To err once is human. To do so repeatedly is incompetence.
1995 K1100LT SE |
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Flying Duck PsyKotic Waterfowl
Joined: 27 Jan 2005 Posts: 10085 Location: Bumf***, WA
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Posted: Sun Dec 20, 2020 2:11 pm Post subject: |
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What he said. The fuel pressure regulator sends extra fuel back to the tank via the return line so it's normal for there to be gas flowing back into the tank.
The fuel pump puts out about 65 psi and the fuel pressure regulator keeps the system at 36 psi. _________________ 93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE |
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1stSSPZ
Joined: 11 Apr 2016 Posts: 4 Location: Lubbock, Texas
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Posted: Sat Jan 02, 2021 4:43 pm Post subject: |
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Well, I have since changed the fuel filter but no luck. Starts right up when cold. Can let it sit and idle for a bit, till the temp gauge gets close to operating temp. Can shut it off but will not restart. It struggles but won’t quite catch. I can also hear a ticking sound while the key is on, sounds like under the left rear of the tank. Never noticed that before but I usually have helmet and ear plugs in...any ideas? _________________ 1985 K100rs, 94 K1100rs, 98 K1200rs, 01R1150gs |
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Flying Duck PsyKotic Waterfowl
Joined: 27 Jan 2005 Posts: 10085 Location: Bumf***, WA
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Posted: Sat Jan 02, 2021 5:30 pm Post subject: |
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If it dies once it warms up and then starts again when it cools back down then that's often a symptom of a dying Hall Effect sensor.
Throw some cool/cold water on the HES cover plate when it dies and see if that makes a difference. The HES cover plate is the square cover on the upper right of the front of the motor.
_________________ 93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE |
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Grunter Flying Brick Rider
Joined: 30 Sep 2015 Posts: 368 Location: North East England
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Posted: Sun Jan 03, 2021 4:48 am Post subject: running then not |
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Mine actually turned out to be a bit more complex than a Hall sensor and a problematic fuel connector.
IT had exactly the same symptoms as yours, which first became evident on the descent of a hill where the throttle was shut for a while or just slightly open. The motor would lurch when I opened up or actually cut out if I went to change gear.
I also had the problem (assumedly linked) where I could start the engine and it would run quite happily on idle until it warmed up then just cut out. It would start immediately without hesitation and continue running so long as I held the throttle slightly open.
BMW diagnostics could not find anything wrong with it even when it was in their workshops and the fault occurred. They thought of the Hall sensor and fitted a known good one with no difference, the problem still persisted.
I took the bike away and eventually sold it to someone who wanted the engine to fit into a trike. I never found out if he had cured the problem.
I have had a Hall sensors die on both of my K75's and the failure was instantaneous. One second it was working the next it was dead! I wasn't aware they gave a warning before failing. _________________ 1997 K1100LT
1994 R1100RS
Last edited by Grunter on Sun Jan 03, 2021 9:54 am; edited 2 times in total |
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Scott_Anderson Site Admin
Joined: 05 Sep 2006 Posts: 3119 Location: Central Iowa, USA
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Posted: Sun Jan 03, 2021 6:58 am Post subject: |
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Not saying this is your problem, but I once had fuel pump issues caused by a dirty connection at the Motronic multi-pin plug.
Cleaned it real good with some electrical contact cleaner and a tooth brush, then applied a small amount of dielectric grease and it hasn't skipped a beat since.
The purpose of the 'non-conductive' grease is 2 fold... being non-conductive it won't short circuit adjacent contacts, and 2ndly it keeps moisture out of the connections to prevent corrosion from occurring.
Good clean ground connections are your friend as well. Under the fuel tank, at the starter, and on the battery. _________________ Ride safe.
1995 K1100LT 0302044
1997 R1100RT ZC62149
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.) |
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1stSSPZ
Joined: 11 Apr 2016 Posts: 4 Location: Lubbock, Texas
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Posted: Sun Jan 03, 2021 1:06 pm Post subject: |
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Scott_Anderson wrote: | Not saying this is your problem, but I once had fuel pump issues caused by a dirty connection at the Motronic multi-pin plug.
Cleaned it real good with some electrical contact cleaner and a tooth brush, then applied a small amount of dielectric grease and it hasn't skipped a beat since.
The purpose of the 'non-conductive' grease is 2 fold... being non-conductive it won't short circuit adjacent contacts, and 2ndly it keeps moisture out of the connections to prevent corrosion from occurring.
Good clean ground connections are your friend as well. Under the fuel tank, at the starter, and on the battery. |
Had an old K100rs that would exhibit these symptoms on occasion and a good cleaning of the moronic connector would do wonders. I will try that again. I have also replaced the HAS with no affect. I have a fuel pump om the way from Euro-electics. _________________ 1985 K100rs, 94 K1100rs, 98 K1200rs, 01R1150gs |
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Flying Duck PsyKotic Waterfowl
Joined: 27 Jan 2005 Posts: 10085 Location: Bumf***, WA
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Posted: Sun Jan 03, 2021 1:49 pm Post subject: |
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From the symptoms you describe (runs well until warm) it's not going to be a bad fuel pump issue.
The other place wiring to the fuel pump can go bad is in the fuel level sender at its base. You can run jump wires directly to the terminals on the fuel pump to diagnose that. Of course attach the wires to the fuel pump before giving them any power as you want to be 100% sure you don't generate a spark in the fuel tank and turn your bike into TWA Flight 800. Note that the smaller diameter terminal on the fuel pump is 12V+ and the larger diameter terminal is ground. _________________ 93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE
Last edited by Flying Duck on Mon Jan 04, 2021 2:43 am; edited 1 time in total |
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Jim Site Admin
Joined: 17 May 2003 Posts: 3840 Location: WHERETHEFUNNEVERENDS
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Posted: Sun Jan 03, 2021 7:47 pm Post subject: |
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SKDonlan and I both had the issue with the fuel sender.
The connection inside the white plastic base goes bad and starts arcing. I think I posted pictures of mine after it failed on the way to Atlanta. There were dark areas in the plastic. New fuel sender sent overnight fixed the problem.
I will say the problem was intermittent at first - depended on how hot things got if the connection was being made or not. _________________ Jim
1997 K1100LTSE 94,000 - has gremlins!
1995 R100RT Classic 16,650 crashed - repairing
1992 K75RTP 46,000
1992 R100R 24,000 - FOR SALE
"We shall not all die, but we shall all be changed." |
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Al. Flying Brick Rider
Joined: 28 Oct 2005 Posts: 383 Location: West of Ireland
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Posted: Tue Jan 05, 2021 3:18 pm Post subject: |
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Fuel filter _________________ 1994 K1100 LTSE + Blackbird |
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Jim Site Admin
Joined: 17 May 2003 Posts: 3840 Location: WHERETHEFUNNEVERENDS
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Posted: Tue Jan 05, 2021 7:24 pm Post subject: |
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Top post - 12.19.20:
"About a month ago, removed the tank to replace the air filter and replace a cracked fuel delivery hose."
_________________ Jim
1997 K1100LTSE 94,000 - has gremlins!
1995 R100RT Classic 16,650 crashed - repairing
1992 K75RTP 46,000
1992 R100R 24,000 - FOR SALE
"We shall not all die, but we shall all be changed." |
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InfamousRiding
Joined: 05 Jan 2021 Posts: 8
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Posted: Wed Jan 06, 2021 4:45 am Post subject: |
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Scott_Anderson wrote: | Not saying this is your problem, but I once had fuel pump issues caused by a dirty connection at the Motronic multi-pin plug.
Cleaned it real good with some electrical contact cleaner and a tooth brush, then applied a small amount of dielectric grease and it hasn't skipped a beat since.
The purpose of the 'non-conductive' grease is 2 fold... being non-conductive it won't short circuit adjacent contacts, and 2ndly it keeps moisture out of the connections to prevent corrosion from occurring.
Good clean ground connections are your friend as well. Under the fuel tank, at the starter, and on the battery. |
The same is true for me. Regular cleaning worked afterwards. |
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jarnbak Mad Brick Rider
Joined: 18 Jan 2004 Posts: 85 Location: Helsinge,Denmark
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Posted: Tue Jan 19, 2021 4:31 pm Post subject: |
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I had the samme issue on a 92 k11lt.It was the connector on the dual water temp sensor that had corosion.ecu got a low temp reading so when engine was warm it got a lot of fuel(to mush to run) ok when cold. |
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Acentistaha Brick Rider
Joined: 28 Sep 2017 Posts: 48
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Posted: Wed Mar 17, 2021 11:13 pm Post subject: |
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jarnbak wrote: | I had the samme issue on a 92 k11lt.It was the connector on the dual water temp sensor that had corosion.ecu got a low temp reading so when engine was warm it got a lot of fuel(to mush to run) ok when cold. |
Interesting, I wish you would elaborate. |
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Flying Duck PsyKotic Waterfowl
Joined: 27 Jan 2005 Posts: 10085 Location: Bumf***, WA
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Posted: Thu Mar 18, 2021 11:58 pm Post subject: |
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Acentistaha wrote: | jarnbak wrote: | I had the samme issue on a 92 k11lt.It was the connector on the dual water temp sensor that had corosion.ecu got a low temp reading so when engine was warm it got a lot of fuel(to mush to run) ok when cold. |
Interesting, I wish you would elaborate. |
The temp sensor for the Motronic is installed in the coolant pipe that comes off of the top front of the cylinder head where the coolant exits. (To get the most accurate reading of engine temp.) The resistance from that sensor decreases as the engine temperature increases. If the connection is dirty then the resistance is higher than it should be so the Motronic thinks that the engine is a lot cooler than it really is and puts out too much fuel. _________________ 93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE |
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philosophicalzombie Brick Rider
Joined: 03 Jun 2013 Posts: 44 Location: Mariposa CA
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Posted: Fri Aug 13, 2021 2:30 pm Post subject: |
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Sorry I'm late to this thread and if the OP has resolved then good for them.
I'm reminded of the issues I had with my fuel system several years ago (described here):
http://k11og.org/forum/viewtopic.php?t=11815&highlight=&sid=6e6111ccd1613f98e5a967aa020dbc5c
I also rerouted the fuel return spray, which was shooting fuel back into the tank where it shouldn't be shooting fuel. I'll try to find that thread. - Blake _________________ Blake
Mariposa, CA
1993 K1100RS Mystic Red |
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