I will try to make this short and simple with any information that I feel is relevant, any ideas or thoughts are appreciated. Some background info; I bought the bike non-running with alleged fuel pump issues. So I purchased a second fuel pump instantly before looking into the issue being that the previous owner seemed knowledgeable. The problem ended up being that the connection for the pump going into the tank was disconnected, therefore i had a spare fuel pump. I then had no issues for two years of riding until about 9 months ago my k100 died without any notice after a short 30min ride. It was instant without a hiccup, as if the kill switch was off. Being that it is a strong running bike with 60,000 miles i immediately though i must have ran out of gas. This was not the case, after putting gas in and no success, I checked for spark which it has and decided to change the filter in the tank and later put in the spare fuel pump with the hope that it was a loss of fuel pressure from the pump causing the issue. If i put fuel down the intake it will run as it should until fuel has dispersed. So i am not electrically inclined or familiar with what would cause such an issue. Any ideas what would cause such an issue? I am thinking the fuel regulator, but i think it may be a an electrical issue. It seems the ground wire from the battery to the frame gets hot when cranking. Possibly it has always been this way and i never noticed, and was only brought to my attention by the extra cranking on the engine. Is it a common issue for the connection to the frame to corrode, or become bad in some way? Any insight will be much appreciated, fell free to ask me questions, thank you.

When you try to start the bike does the starter engage and does it turn the engine over?

The grounds [earths] do give trouble and its only a matter of taking them apart one at a time and cleaning them. There are a number under the gas tank and also one from the gas tank to the frame.

There are a lot of issues with electrical connections, arising from the age of the bikes. You probably need to clean and check all of these, Deoxit is good. Don't go at them with any electrical testers without expert advice. I am not expert on these, others here are but if you get it wrong you will do electrical damage.

The problem sometimes is a bad connection can make it appear a sensor is faulty when it is not.

The Hall sensor, if it goes faulty, can give trouble when the engine is hot.

Spark plugs are cheap but the K can be sensitive to their condition. I have seen them gone dud after only a few hundred miles.


92KK

Yes the starter engages and everything seems to work as normal. The fuel pump hums for a few seconds the turns off but i seem to not be getting fuel as i can put fuel down the intake and it will start and run as it should. What would cause such an abrupt stop of the fuel system working?

How good is the fuel filter? Could it be blocked? Sometimes the ethanol in the gasoline destroys the seals inside.

When you do initially go to start the engine the fuel pump pressurises the system and that takes a few seconds. If fuel is not getting through would seem a blockage somewhere....or.... Could the connections be reversed...?

I know on my bike that's easily done. The connections inside the tank are supposed to be different sizes so they cannot be reversed but the secondhand pump you fitted may not have that as some owners modify them to be the same size. you could end up reversed inside the gas tank but with the correct order where they connect to the bike loom under the back of the gas tank. They don't work reversed......



92kk

You might remove the fuel cap assy and be able to look inside with a flashlight. Trigger the starter momentarily to start the fuel pump. Observe that it runs for about 1.5 sec. as desired. Checking further be sure that your fuel pressure isn't squirting out inside the tank due to a burst fuel hose of a cracked fuel filter.
if good.....pull the fuel filter OUTLET hose off the aluminum tube in the tank, reserve the clamp. Hold your left thumb tightly over the end of the filter outlet hose while toggling the starter switch. There should be sufficient fuel pressure at your thumb to push your thumb away and squirt a strong stream of fuel out into the tank. BE CAREFUL when doing this test that your fuel hose end is well contained inside the tank and pointed away from you. There is fire/injury potential from squirting pressurized fuel around. Keep it ponted well inside the tank and away from the opening.
Report back what you see.
regards, Ibj....

I should have noted early that there is one symptom that seems strange. After letting the bike sit for some time, a day or so, it will fire for less than a second as if it were running on fumes. At first i thought it may be left over gas in the intake from me putting gas in there. I believe this is not the case as it happens every time i attempt to start after sitting for a period of time and i have not put gas down the intake for a couple months. I have checked the hall sensor by unplugging it and trying to start the bike. My understanding is that will override the sensor. The fuel pump runs and pressurizes as it should from what i can tell. I have not checked the pressure at the rail yet as i do not have the equipment necessary. It is an OEM pump so there is no way to reverse the connection and it seems to me that with the instantaneous of the engine dieing without notice implies an electrical issue. I never had starting or running problems in the past which would imply a possible fuel regulator spark plug, or injector issue . I truly fill it is an electrical issue, possibly a specific sensor or? The symptoms seem specific enough to get some direction in where i should look. To test the fuel pressure do i need a special fitting or is it a common size? I have yet to pull the fairing and dig deep as i hoped to get some insight before digging deeper into the problem then needed.

This could be an intermittent connection in ether the ignition switch circuit or the kill switch circuit.
Suggest you remove the tank and find the 2 connectors from those switches to the main wiring harness, located (probably) to the right of the frame backbone and about 1/2 way back from the front of the tank, as I remember they may be round in shape possibly having one additional separate single wire connector along side that runs up to the same switch.
Disconnect both of these & clean very thoroughly with De-Oxit5 and reconnect them several times while wet.
finally, push them VERY FIRMLY back together.

Also, you could dis-assemble the right handlebar switch and clean the individual contacts on the kill switch itself.

A somewhat lesser probability can be the internal contacts in the ignition switch which can also be dis-assembled and cleaned of corrosion if needed.
Disconnect, spray with De-oxit and reassemble the main connectors to the ICU ignition unit and the ECU fuel control computer....be sure the metal clip on that "snaps" home securely.

Can I assume that you have already inspected the connection between the fuel tank and the bike harness to be sure that #1 It is completely seated home in the socket and #2 has the internal pins "spread" sufficiently to make them a tight fit into their individual receptacle pins

I would be looking very carefully at the fuel supply system.
Firstly as ibj said check fuel pressure after the pump then after the filter by placing a thumb over the end of the hose and at every place on the delivery line to the fuel rail and then to the pressure regulator which is behind the air filter box and behind the #4 throttle body. the pressure before the regulator should be 65psi without the regulator connected and 33psi. The hose is 8mm or 5/16 which are almost identical.
If you get good pressure there check you are getting a good flow back to the tank as these systems need to have the flow through the lines to work well.
This problem shows no signs of hall sensor and if the hall sensor is disconnected it will NOT start.
The bike has been sitting for a while so the problem now could have no relation to the original problem and these bikes are prone to fuel problems if let sit for any lengthy time without proper layup procedures.
Check the injectors are not blocked as ethanol can actually disolve the inner lining of the old lines and then it clogs the tiny pre filter on the injectors.

Are these issues all related?
https://www.k100-forum.com/t6211-premature-ejaction#70764

https://www.k100-forum.com/t1879-bike-keeps-cutting-out

https://www.k100-forum.com/t4309-k100-starts-and-dies

I would strongly suggest you go to the Portal for this site and select K100 2V EFI Electronic Ignition Troubleshooting. Work through step by step it is quite simple and that should lead you to the solution let us know if you have a problem understanding anything and if you can get a cheap voltmeter that reads up to say 15 or 20 volts for use as a diagnostic tool that will make the testing easy. A needle type with a pointer is better than a digital one because it is more effective at showing fluctuating voltage signals. There is a post from me "Using a test meter volts amps and ohms" in the How to that is worth a read if you are not that familiar with using a test meter.
Regards,
K-BIKE

My money is on the coolant sensor at the radiator. We have seen an increased number of bikes having this fault. The connection gets rusty and falls off. Also, no one has yet said to ensure the connections at the main brain box under the seat are fully connected. It's one big gang plug. Easy to look and see...

agree  clubbie
and really easy to clean up the pins that project out of that under seat computer thang

just get some fine wet and dry ...wrapped along a thin wooden strip ..(what we call paddle pop sticks ) ...and clean up all the flat faces ,  carefully ...then spray off the residue with "plastic safe " electronic cleaner spray ..get some deoxit to finish the job ...the gold will give a bit more protective coating

don't forget to do the socket part in the plug connection with deoxit as well  ...solved a couple of issues for me

good luck !

Have you checked the injectors are getting power? I had the same problem, there's a starting trouble shooting guide somewhere that tells you which pins on the unit under the seat that should give 12v to the injectors, i connected a lamp to it and it was not turning on. Only comes on when you press the starter too.

I changed the fuel injection relay and it seemed to work.