K75 Quit and won't start

[PaulF]

K75, 86', hit a small bump on the road and then it died. Now it won't start. It will turn over but not fire.
Determined the fuel pump is not running. I powered the fuel pump directly and it runs. There is no power at the fuel pump fuse. Working through the wiring I have determined there is power to the #86 pin on the fuel injection relay. If I ground the #85 relay pin the relay engages. I have tested the relay on it's own and it seems to be working. The yellow/brown wire from the # 85 pin goes to the igntion control unit. I assume something in this unit grounds the connection to energize the relay. I have clean the wire plug to the ignition control unit and checked the wire plug to the fuel igjection control unit.
Still won't start. Stumped! Any suggestions?

Thanks

Paul

[tv guy]

My first guess is the tank connecter got knocked loose or off by the bump. It plugs in under the fuel tank.

If that's not it, check the fuses I've had them work loose and fall out of the connecter!

[motoedde]

Have you checked the connector between the overflow bottle and the tank for connectivity problems?

Visually check it as that connector is a spring loaded one and fatigues over time...

[mrich12000]

Chec the wire bundle under the fuel tank. Check the riht handle grip wires look for the green corrosion in the connectors also check the fuel pump grounds
Kepp us informed .

[deilenberger]

K75, 86', hit a small bump on the road and then it died. Now it won't start. It will turn over but not fire.
Determined the fuel pump is not running. I powered the fuel pump directly and it runs.
You did this at the tank connector? If so - we can discount the connector being loose or not connected.
There is no power at the fuel pump fuse. Working through the wiring I have determined there is power to the #86 pin on the fuel injection relay. If I ground the #85 relay pin the relay engages.
Does the pump run when the relay engages?
I have tested the relay on it's own and it seems to be working. The yellow/brown wire from the # 85 pin goes to the igntion control unit. I assume something in this unit grounds the connection to energize the relay. I have clean the wire plug to the ignition control unit and checked the wire plug to the fuel igjection control unit.
Still won't start. Stumped! Any suggestions?

Thanks
PaulPaul,

It sounds odd - but I'd suggest removing the starter, disassembling it, and cleaning it. There are some decent instructions on www.ibmwr.org - under K-tech.

The control circuit for the fuel pump relies on a ground signal from the ECU when the engine is running, and by the voltage going to the starter when you go to start the bike. As odd as it sounds - excessive carbon deposits inside the starter brush assembly can keep the fuel pump from running.

When you have really ODD electrical problems on an early K bike - it is frequently related to a carbon'd up starter. Often a big bump will dislodge some carbon causing a leakage path - and the symptoms appear.

DO MARK the sections of the starter relative to each other before disassembly.. people have gotten them back together so they run backwards, and then wonder why the starter is spinning but not engaging the engine.

HTH,

[PaulF]

Don

Yes I put power to the fuel pump at the tank connector.

I had the tank removed when I engaged the relay so I couldn't see if the pump ran.


I'll try cleaning the starter and see if that helps. Thanks for your help.

Paul

[tommcgee]

The control circuit for the fuel pump relies on a ground signal from the ECU when the engine is running, and by the voltage going to the starter when you go to start the bike. As odd as it sounds - excessive carbon deposits inside the starter brush assembly can keep the fuel pump from running.

I love it!

Your toe bone connected to your foot bone,
Your foot bone connected to your ankle bone,
Your ankle bone connected to your leg bone,
Your leg bone connected to your knee bone,
Your knee bone connected to your thigh bone,
Your thigh bone connected to your hip bone,
Your hip bone connected to your back bone,
Your back bone connected to your shoulder bone,
Your shoulder bone connected to your neck bone,
Your neck bone connected to your head bone,
I hear the word of the Lord!

[PaulF]

Update - I cleaned the stater but the relay still does not energize the fuel pump.

I assume the problem is lack of grounding through the electronic brains. I'll try cleaning all the ground points and hope the problem isn't the electronic parts.

I am off the Finger Lakes for a few days so I get back to it when I return.

Paul

[chris_d]

Paul,

I had a similar situation a few years back...found a pin had 'dropped' out of it's detent in the fuel pump relay socket. (or was never inserted properly in the first place)

Get under the relay box and see if any are loose... 'push' the pins back up into the socket.

Good luck!

[barryg]

On my 87 K100 at one time or another my bike would not start or would die unexpectedly. One of these instances just unplugging and plugging my ICU several times solved the problem. Once it was the drity starter somebody allready brought to your attention. Took mine out, took it apart cleaned it and that solved the problem. Several years ago mine would die unexpectedly just riding done the road. Long story short in was a problem in the fuel sending unit, had a short in that pod of wires coming out of the tank. New fuel sending unit solved that problem. You will get yours solved. Goodluck

[Troutluck]

Happened to me once. The "brain" was not seated correctly.

[breyfogle]

....Yes I put power to the fuel pump at the tank connector.....

Three suggestions:

1) If you separated the 4-pin connector at the tank and applied power to the tank-side pin that goes to the fuel pump, you did not test the plug itself. The pins in this plug are known to weaken over time such that male and female sides don't make good contact (or any contact). If you re-assemble the plug and apply voltage to the output pin on the relay, you can verify the plug is good and the fuel pump is good.

2) The ICU does ground the fuel pump relay but only if it sees a valid signal from the Hall sensor and the ICU is working. It's very rare, but I had an ICU actually fail. It would not ground the fuel pump relay control circuit. Symptoms were just like yours: crank and crank but no fuel pump so no start.

3) Another test would be to hot wire fuse #7 directly from the battery. This will run the fuel pump. With the fuel pump running, try to start the engine. If it starts, the ICU might be bad.