K11 Owners Group

Porkchop · Joined: 15 Mar 2012 Posts: 3

Hello all, I'm trying to troubleshoot some fuel pump issues on a 93 K1100LT. Does anyone have a pinout diagram of the wiring for the fuel pump/relay/injectors/motronic?

the green/white wire on the 4pin fuel tank connector is not receiving any voltage to prime/run the bike and there is a continuity to chassis ground. I've manually stripped back the wiring harness and inspected the wiring, with no shorts or other irregularities. The relay checks out fine and there are no issues there.

What I am trying to figure out is why I have a ground continuity on the green/white wire that runs from the fuel pump relay and goes to the motronic computer and fuel injectors.

Thanks

Inge K. · Posted: Thu Mar 15, 2012 10:04 pm Post subject:

Wiring diagrams.

Inge K.

Porkchop · Joined: 15 Mar 2012 Posts: 3

Thanks!
Traced all the wiring in the harness and nailed down the problem.

In addition to the 4 pin connector being bad, the Motronic was only giving 1-2V of juice to (not quite) click over the fuel pump relay. Turns out that the Motronic had some internal condensation buildup/corrosion (the bike had been sitting in the weather for some time before I picked it up) which was inhibiting operation.
I pulled the Motronic apart and did some spot cleaning with a toothbrush and contact cleaner, air dried and then put in the oven for an hour at 170F.
Purrs like a kitten now!

Oddly enough, with the Motronic not operating the fuel relay, everything else was operational, as I was able to fire and run the bike on starter fluid while diagnosing the issue.

Stoked Steve · Posted: Sun Mar 18, 2012 3:33 pm Post subject:

This just goes to show what comes up over and over again, that rarely do major components, like the Hall Effort Sensor, the Motronic brain, the ABS brain, the coils, or other items fail.

90% of the time, it's just bad connectors, bad grounds, bad batteries, or broken wires causing the issues...

It can drive you nuts trying to figure it out and worrying about some expensive component needing to be replaced.
_________________
Steve
Virginia Beach, VA
93 K1100RS Mystic Red SOLD
12 Suzuki DL650A VStrom

Porkchop · Joined: 15 Mar 2012 Posts: 3

That is true, although I was very lucky that the condensation buildup did not short the Motronic.
I had to physically disassemble the Motronic to eliminate the condensation on the board and minor corrosion.

In any case, she's purring like a kitten!

Stoked Steve · Posted: Tue Mar 20, 2012 8:13 am Post subject:

You were pretty brave to open that up! I didn't even know it could be opened, good job!
_________________
Steve
Virginia Beach, VA
93 K1100RS Mystic Red SOLD
12 Suzuki DL650A VStrom

Tony627 · Joined: 21 Jul 2010 Posts: 20 Location: Kent, England

I wonder if you can help. Having read so much about this problem. My fuel pump seemed to be just about turning over to prim but the bike did not start. It bench ran ok. I got a replacement, bench tested it and it was fine. fitted it.... same fault. Check the wiring on the sender unit,, seems ok.........Any thoughts?

Also I have some brown wires in a black outer which run ourt of the rear of the motronic plug under the seat. They have a washer type connector on them. It bends to the left (nearside uk) of the bike once again any thoughts as the where it connects to?

Regards and thanks in advance.

Tony
_________________
He who laughs last didn't get the joke in the first place!!

1995 K1100LT alias 'Big Red'

Scott_Anderson · Posted: Fri Apr 27, 2012 8:09 am Post subject:

Tony, brown wires are ground wires. They should end at a frame connection.
There are a couple frame connection points. 1 is under the fuel tank near the front, 1 is at the rear of the starter.
There may be a couple of ground wires connected at the battery, but not too many.
_________________
Ride safe.

1997 K1100LT 0302488
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
1995 K1100LT 0302044(R.I.P.)
1997 R1100RT ZC62149(sold)

Inge K. · Posted: Fri Apr 27, 2012 9:58 pm Post subject:

About malfunctioning fuelpump: have done a real good good check on the four pin connector to the tank, as this is a well known problem source.

About brown wires: if it`s four of them....and one got blue tracer, next green tracer and last 2x black tracer, it`s for the diagnostic connector..modded by PO.

Inge K.

Tony627 · Joined: 21 Jul 2010 Posts: 20 Location: Kent, England

Hi Scott and Inge

Thanks for the tips, problem solved...... I connected the lead to the earth on the battery and the fuel pump wizzed into life and started first time. This has been going on for some time and finally wjth your help I got to the bottom of it..... Incidentally I purchased a fuel pump from a 3 series BMW for £15 and it worked. If anyone would like the details I would be happy to help.

Regards

Tony
_________________
He who laughs last didn't get the joke in the first place!!

1995 K1100LT alias 'Big Red'