Out of the blue, the bike doesn't want to start. Once I hit the button there is an initial pop, but then it continues to crank and crank. If I hold the throttle wide open and crank it for a good few seconds it fires up and smells like it's flooded. I noticed a small gas puddle near the center stand. Once I get it going it seems to run fine. As soon as I shut it off and try to restart I get the same problem. It's my daily rider for the past 9 years and there was no indication of any problems. Yesterday it fired like a top, today nothing but trouble. I'm just not very good at troubleshooting, I was hoping somebody might have some insight on what it might be.

Check the temperature sensor values and check if the sensor plug is clean and has a good connection.
Regards Martin.

I will check that, thanks. Would that affect it from a cold and warm start?

Yep it's one of the known sources of flooding. Another one is a sticky injector/s that doesn't fully close on shut down.
Regards Martin.

Thanks for the input, Martin. That will give me something to work on in the coming week.

Well I have checked the temp sensor & plug voltage, they both seem to be working ok. Pulled all the injectors and checked them, they seem ok. I connected them back to the fuel rail and hit the ignition, they all seem to spray evenly and shut off all the same. Maybe somebody may have some other suggestions, I would sure appreciate it. I'm not sure where to go from here. I'm no mechanic but I do enjoy doing my own work and learning a thing or two in the process. It still floods when starting, fuel dripping out of the manifold after cranking for a bit.
Thanks for any input.

Is your start button intact and still “springy“? They don’t seem to be happy running when left in the depressed position...

Regard

Dan

Was the fuel spraying on and off, or a constant spray, I'm guessing on off.

You might have a blockage in the fuel return line, raising the pressure. With the fuel cap assembly removed, can you see fuel returning to the tank? There is a recent thread like that "another k100 running too rich"

Well, no luck yet. I did notice the vacuum line going to the FPR was somewhat dry and cracking, so I replaced that. Then I did a fuel pressure test. Even though it won't start, it was reading 39 or 40 psi, while it was cranking. I also tried disconnecting the idle switch and starting- no difference there either.  I really appreciate all of the help, but I may have to rely on professionals to figure this one out for me.

Also you might have constantly open injectors, which is rare,  but easy to check.

Some people here (not me) are also professionals.

Did you check the return hose like Martin mentioned?

You might be able to get it going with the fuel pump electrical connection unplugged if constantly open, I guess the reading is high for this problem though.

While cranking, with a screwdriver to an injector and its handle to your ear you should hear the ticking sound of the injectors turning on and off.

Or while cranking, using a (12V) computer safe test lights clip on battery positive and probe to the loom of an injector plug,  the light should remain off at one pin,  and flash on/off at the other.

The pin that remains off would be power (positive to positive) The other pin (earth, as in the photo) should flash on and off.

Hi

What about the battery?
How old is your battery? Perhaps it’s time to replace?
Might have enough charge to turn the motor. But not enough for all the electrical systems.

I hadn't mentioned the hose to Martin as I didn't noticed it yet. I had pulled the fuel rail with the injectors connected and they all sprayed and shut off equally. Would a low battery cause it to flood?

I did not check the return hose yet. Would the fuel come back into the tank if it's not starting, only cranking? I also had replaced the spark plugs after realizing it had been a while since I did that.

A couple of years ago, I did have a low power battery that would crank quite a bit but not start the bike. A jump start fired it right up, so I replaced it. However I don't recall the flooding and fuel dripping underneath.

Also I didn't mean to infer that there were not professionals on this forum, I was only referring to myself and lack of knowledge. Sometimes I doubt myself testing these things, whether or not I'm doing it right.

Fuel should return to the tank, even while cranking.

Multiple failed attempts to start could cause flooding, but fuel leaking out the headers seems an excessive amount.

Couple questions:

1. you mention checking the Temperature sensor voltage.  You should be checking resistance in ohms.  A cold engine should give a reading of 2500 ohms, at running temperature it should be about 250 ohms.

2.  what kind of spark plugs are in the engine?  KGK D7EA are good plugs, but have been known to cause problems if they don't have the "terminal nut" installed on the terminal where the plug wire connects.

3.  Have you pulled the spark plugs to see what the electrodes look like?  Are they sooty and black, wet, or normal tan/light brown?

I did check the resistance on the sensor. I probable meant to say I checked the plug for the sensor to make sure I didn't have a bad ground. I did just put in the NGK D7EA plugs, I added the terminal nut from another new set of plugs. The old plugs looked like a fairly normal wear.
I also wondered if anybody knows why I can't seem to see any of the photos that anybody has posted on the forum. They are all some blank image of a mountain.

Have a look at the technical guides located on the first page of the “how to” section of the forum.
I suggest clean and degrease all connectors including under the petrol tank. Unplug the ecu and ignition control unit and use the connector plug to check for continuity.
Check Ground points under petrol tank.
Do not apply a multimeter to the ecu and ignition units, only the connectors.
Use the technical manual to guide you.
Make certain your battery is in good condition

LE-JETRONIC-DIAGNOSIS-TEST-EQUIP



 Gabriel

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Thanks Gabriel, I will look into that

OK so today I put the battery on charge while I got to work. I started with checking the ECU connection, it looked pretty clean, but i cleaned it anyway. Then, I removed the gas tank and removed the ignition control unit, checked the connections, and cleaned them. On the ICU connections, a few of the tabs looked a little dark while the others looked pretty shiny, so i cleaned them pretty thoroughly. Then I proceeded to remove the ground bolt under the tank with several wires connected to it, and thoroughly clean all of the connections and put it back together. Then I removed the air box to check the fuel return hose, which was not blocked up, but it did have some dry cracking, so I replaced it. After that I put the tank back on, the battery back in, made sure everything was connected, and thought "Well, here goes". I was actually fairly surprised when it fired right up. Sounded pretty smooth as well. I can't thank you guys enough for all of the help and suggestions. I wish I knew what the final solution was, but I won't linger on it too long, just happy it's up and running again.
Happy riding everybody!

Well done!  Enjoy...l