K11 Owners Group

[dhink]

I need some help from the brain trust. To give you a little background, my 1993 K1100LT has been sitting in the garage collecting dust for several years. I'm ready to get it back on the road so, I removed the tank, clean it out, replaced the fuel pump and rubber holder, and replaced the fuel filter. The sender was completely corroded so I cleaned it up and replaced the wires to the fuel pump. The windings for the fuel gauge were bad so I decided to leave the float and power wires to the windings off for now. From reading through other post regarding issues with the sender, I've replaced the connector with a flat 4 wire trailer connector. I plugged the connector in, turned on the key, flipped the kill switch and no sound from the fuel pump (even with the clutch pulled in and hitting the start button. Starter spins and engine turns but nothing on the fuel pump hot lead.) Checked the side stand switch to ensure it was working and when down no continuity when up I have continuity. The fan comes on when the kill switch is flipped so I swapped the fan and starter relays and still had power on the fan but no power to the fuel pump. My next step was to check voltage at the sending unit connector on the frame. I'm getting 12v on the white wire, 8v on the yellow wire but 0v on the green w/white stripe wire. I get the same reading no matter if I use the brown wire for the ground or the frame itself. The one thing I found interesting is that I flipped my meter to continuity and connected one lead to the brown wire and as I expected no continuity with the white or yellow but I'm getting continuity between the brown and the green w/white stripe wire. I removed the lead from the brown wire and touched it to the frame and again, continuity. This is with the sending unit connector disconnected so it's not a loopback through the fuel pump. My next step was to remove the relay and retest and I got the same results. I also check continuity between the green w/white stripe wire between the relay and the end at the sending unit connector and I do have continuity there. Next, I removed the plug from the Motronic and the results were the same. I checked all of the fuses and they are all good. I'm getting 13v across each fuse. My questions are 1. why am I getting continuity between the hot wire for the fuel pump (green w/white stripe) and the ground (brown) and 2. what should I check next to find out why no power to the fuel pump hot wire (green w/white stripe).
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

The white and yellow wires have absolutely nothing to do with fuel pump operation. Ignore them. (Yellow is the fuel level to the gauge and white is for the low fuel warning lamp in the instrument cluster.)

Fuel pump 12V power comes from the green/white wire and grounds via the brown wire.

Fuel pump power goes through Fuse 6. When the starter motor is turning the engine you should have 12V at the rear terminal of Fuse 6.
_________________
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

[dhink]

Flying Duck, Thank you for your reply.

As I stated in my original post, I tested at the fuse and I'm getting 13v at the fuse but nothing at the green w/white stripe wire at the connector for the tank (testing at the harness on the bike to eliminate any possible issue with the connector itself or the sending unit.)

My questions are:

1. why am I getting continuity between the hot wire for the fuel pump (green w/white stripe) and the ground (brown). This is with the connector to the tank disconnected, the relay for the pump removed, and the Motronic disconnected.


2. what should I check next to find out why no power to the fuel pump hot wire (green w/white stripe).

Thanks!
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

Check for continuity from the green/white wire of the tank side of the connector and the smaller diameter terminal on the fuel pump.

Check for continuity from the brown wire of the tank side of the connector and the larger diameter terminal on the fuel pump.
_________________
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

[dhink]

The issue has nothing to do with the wiring in the tank.

I have continuity between the ground lead on the fuel pump negative terminal and the brown lead coming out of the sender and I have continuity between the positive terminal on the fuel pump and the green w/ white stripe wire coming out of the sender.

I can connect the leads from the tank directly to a power source and the pump comes on.

The problem is on the bike side wire harness.

No power to the green w/white stripe wire at the connector point for the sender when you flip on the kill switch nor when you hit the starter.

I'm also concerned that I'm getting continuity between the brown wire and the green w/white stripe wire at the connector point as I would not expect this based on there not being any type of loop back that I can think of. The harness side connector is disconnected from the sender side connector, the relay has been removed and the Motronic is disconnected.
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

Current flows through the fuel pump. That's what makes it run. If it didn't have continuity between the pos and neg terminals then it wouldn't run.
_________________
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

[Flying Duck]

Did you or a prior owner add a fan switch? The fan should not be coming on.
_________________
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

[dhink]

I've owned the bike for 20 years. The fan has always kicked on when you flip the kill switch and the air temp is in the 80's or above.
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

The radiator fan should not come on until the coolant temperature reaches 221F.
_________________
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

[dhink]

You're fishing in the wrong pond. I can go into the garage right now, flip the kill switch and the fan will not come on. The reason, the air temp is below 80. As I said, this is the way my fan has operated for the entire 20 years I've owned the bike. When it's hot outside, the fan kicks on, when the kill switch is flipped, prior to starting. Once the bike is running for a few min. and the coolant starts to flow, the fan kicks off. Then it doesn't kick back on until the coolant temp is over 200.
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

I'm not fishing in any pond. I'm telling you the truth.

If your fan comes on at 80F then there is something wrong with your K1100.

Here's how the cooling system is designed to work:

There is a temp sensor in a metal pipe where coolant exits the cylinder head in order to monitor the engine temp.

The resistance of that temp sensor is monitored by the Motronic. As the temperature sensor gets warmer its resistance decreases. (Motronic pins 21 and 32 are where the temp sensor wires enter the Motronic.)

When the resistance between those pins tells the Motronic that the coolant temp gets above 221F (105C) the Motronic grounds a blue/yellow wire (from Pin 16) that triggers the fan relay to turn on the fan.

When the coolant gets back down below 221F the Motronic cuts off that ground to turn off the fan.

None of this functionality is impacted in any way by how many years someone has owned a motorcycle.

As you can see in this table from the BMW K1100 Repair Manual the fan does not kick in until the coolant reaches 105C (221F).


_________________
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

[dhink]

Thank you for your replies but you continue to go down paths that have nothing to do with the questions and details I have posted. I don't know if the original owner installed a separate thermostat that kicks the fans on initially if the air temp is over 80 or what but I can assure you that that is the way the fan has operated for the 20 years I have owned the bike regardless of what the manual says.

The issue I need help with is the hot lead (green w/ white stripe wire) that provides power to the fuel pump.

1. why am I getting continuity between the hot wire for the fuel pump (green w/white stripe) and the ground (brown). This is with the connector to the tank disconnected, the relay for the pump removed, and the Motronic disconnected.


2. what should I check next to find out why no power to the fuel pump hot wire (green w/white stripe).
a: Would it be safe to simply remove the lead that is in the wire harness from the relay (there are 2 green w/white stripe wires going to the same terminal on the relay the one to the tank connector and the other to the O2 sensor) and run a new wire directly from the relay to the tank connector?
b: would doing this affect any other circuits?
c: could the O2 sensor be causing the grounding loop showing continuity between the hot wire for the fuel pump (green w/white stripe) and the ground (brown) that I'm seeing at the tank connector?
_________________
Dan Hinkebein
1993 K1100LT

[dhink]

I had a few min. so I ran out to the garage and decided to disconnect the O2 sensor. With the O2 sensor disconnected, I no longer have continuity between the hot lead and the ground lead to the fuel pump. But, I'm still not getting power to the hot lead. I do have continuity between the hot lead (green w/white stipe) at the fuel tank connector and the other end of the green w/white stripe lead at the relay.
_________________
Dan Hinkebein
1993 K1100LT

[Jim]

Dan - I'm not sure your 93 has the same connector at the bottom of the tank as the 97. A round white plastic piece the wires for the sender and the pump go through. There are connections embedded in the plastic that are known to fail on K bikes.

If you see any sign of heat in the white plastic, that's the problem. It's been a long time since I had a failure there - but I'm fairly certain the wires for the sending unit and the pump go through there.

There's a picture of the piece in this thread:

https://k11og.org/forum/viewtopic.php?p=91372&highlight=#91372

Stoked Steve had a failure there - so did I. Worth checking. I know Steve wrote about it - so did I, but I can't find either post right now.
_________________
Jim
1997 K1100LTSE 94,000 - has gremlins!
1995 R100RT Classic 16,650 crashed - repairing
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

[dhink]

Jim,
Thank you for your reply. I have seen many posts regarding failure of the tank connector. I have replaced the connector already, with a flat 4-way trailer connector.

At this point I believe something isn't triggering the relay to close. I tested the spades on the relay block. On spade 6 (pin 30 on the relay) I get 13v. On spade 10 (pin 86) I get 13v when kill switch is on. On spade8 (pin 85) I get 13v with the neg lead in spade 8 and positive lead to the battery.

With the relay plugged in. I put a jumper wire between the Green w/white stripe wires (under spade 7 (pin 87) and spade 6 (pin 30). The fuel pump comes on and fuel is getting to the fuel rail, but the injectors are not firing.

Looking at the schematic for the relay, I believe it's showing there are 2 switch circuits inside. The switch that closes to send power from pin 30 to pin 87/87b (one going to the fuel pump and the other going to the ECU and the switch that closes between pins 85 and 86 which connects the side stand circuit to the ECU.

It appears that everything is present to close the relay but that is not happening. I've swapped relays around but that has not changed anything.

I think my next step is to jumper pin 85 to pin 86 and pin 30 to pin 87 and see what happens.
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

Here's how NO (normally open) relays, like the relays in a K, work:

When you have 12V at 86 and ground at 85 it energizes a coil that connects the source, usually 12V at pin 30 to the output pin 87.

Therefore it is a BAD idea to short pins 85 and 86.

Here's how the fuel pump relay works for a 93 LT: (94 and later are wired differently)

When the kill switch is on and side stand switch is closed it sends 12V to the 86 pin. (Green/red wire)

When the Motronic grounds pin 85 (blue/brown wire) that energizes the relay coil to close the circuit sending 12V power from pin 30 (red/green from Fuse 6) to green/white wires (pin 87) that power the fuel pump, fuel injectors and oxygen sensor.

If you jump 85 to 86 in the fuel pump relay socket that will short 12V to the Motronic via the blue/brown wire which is designed to be a ground wire. This may or may not damage the Motronic control unit.
_________________
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

[Jim]

Dan - believe it or not - I read your post - I know you replaced the 4 pin connector. Apparently you didn't read mine.

I'm not talking about the 4 pin connector - I'm referring to the plastic bit on the bottom of the tank that has soldered connections in it. This where the wires go from outside the tank to inside the tank. Either they overheat or water gets in there and trashes the connection - not sure which. At any rate, if your 93 has the same sending unit as the 97 (I believe it does), get a new sending unit.

If you click the link I posted and scroll down, you'll see a picture of the white plastic piece that has the connections inside. When the connections in that plastic bit fail, the fuel pump will not run.

[dhink]

So, I thought I would close the loop on this one. Turns out the Motronic unit was the issue. It was not sending the ready signal to the fuel pump relay so that the relay would close and energize the fuel pump circuit and also would not fire the injectors.
_________________
Dan Hinkebein
1993 K1100LT

[Flying Duck]

So did you replace the Motronic?
_________________
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

[dhink]

Yes. And now the bike runs great.
_________________
Dan Hinkebein
1993 K1100LT