Hello,

My recently acquired k100 is having some new troubles. I rode the bike to the adirondacks after an oil change, spark plug replacement, and a new fuel filter. The bike ran great all the way. After sleeping and hiking I tried to start the bike but to know avail.
When I turn the key, lights come on as they should. I press the starter and the bike cranks trying to start. If I tap the starter I hear the fuel pump working. I pulled the plugs and checked them against the engine all have good blue spark. I opened the tank to see if the fuel pump had stopped moving fuel, but was still making sound. So I disconected the in tank fuel line before the filter and holding inside the tank cranked the engine. Fuel shot out of the tube at a very high rate. At this point my friend pulled out starting fluid since we had confirmed spark and airflow. Spraying starting fluid into airbox resulted in the engine running but only so long as starter fluid was being sprayed. I pulled the plugs again to check for spray this time and found that the injectors were not spraying. I am new to the bike and am unfamiliar with the path between the fuel pump and the injectors. At this point I am riding back with my friend and will bring a trailer to get the bike back. Any suggestions on how to get it running or what the problem could be would be great.

P.s. sorry for the long post, but I wanted to outline the whole process just in case I might have tripped something that could affect the diagnosis.
P.p.s
I didn't have an ampmeter to check the electronics during this time, so I am unaware if this could be an electrical problem.

Could be a broken fuse #1, the top fuse, or the relay for injection, need to lift the tank to reach it.

Also take note of this page; http://www.kforum-tech.com/electrical/EFI/bike-wont-start-EN.htm

I forgot to mention that I did check all fuses and none were blown, had a few extra in my toolkit just in case. I will make sure to check the relay, and am now looking at the linked page.
Thank you

You may see plenty of fuel coming out the hose, but the pressure may be too low. I ran into this about a year ago and changed out the pump and then it would start.

Glenn

Sometimes fuses don't work even though they havn't blown.

Can you see fuel returning to the tank when the pump runs?  No returning fuel may indicate a weak pump, and/or a plugged filter.  If fuel comes back to the tank when the pump is running, the chances are good there is fuel in the rail with enough pressure to make the engine run.

Has the big connector on the ECU gotten loose?  That can affect the injector signal.

The fact that the engine has suddenly stopped working tells me that the problem is probably a loose electrical connection.  Along with the big ECU connector, I would check and clean as many connectors as possible, as well as the bike's ground connections at the transmission above the shifter and on the frame backbone under the tank. 

It behooves you to find the problem in case it is a loose connection.  They can create intermittent problems that can make the bike maddingly unreliable.

John A wrote:Hello,

My recently acquired k100 is having some new troubles. I rode the bike to the adirondacks after an oil change, spark plug replacement, and a new fuel filter. The bike ran great all the way. After sleeping and hiking I tried to start the bike but to know avail.
When I turn the key, lights come on as they should. I press the starter and the bike cranks trying to start. If I tap the starter I hear the fuel pump working. I pulled the plugs and checked them against the engine all have good blue spark. I opened the tank to see if the fuel pump had stopped moving fuel, but was still making sound. So I disconected the in tank fuel line before the filter and holding inside the tank cranked the engine. Fuel shot out of the tube at a very high rate. At this point my friend pulled out starting fluid since we had confirmed spark and airflow. Spraying starting fluid into airbox resulted in the engine running but only so long as starter fluid was being sprayed. I pulled the plugs again to check for spray this time and found that the injectors were not spraying. I am new to the bike and am unfamiliar with the path between the fuel pump and the injectors. At this point I am riding back with my friend and will bring a trailer to get the bike back. Any suggestions on how to get it running or what the problem could be would be great.

P.s. sorry for the long post, but I wanted to outline the whole process just in case I might have tripped something that could affect the diagnosis.
P.p.s
I didn't have an ampmeter to check the electronics during this time, so I am unaware if this could be an electrical problem.

Can you post up model and year or put in your signature. Ks differ significantly and without knowing the model/year or VIN you will get conflicting answers.

As suggested its most likely to be an electrical issue.

92KK 84WW Olaf wrote:

John A wrote:Hello,

My recently acquired k100 is having some new troubles. I rode the bike to the adirondacks after an oil change, spark plug replacement, and a new fuel filter. The bike ran great all the way. After sleeping and hiking I tried to start the bike but to know avail.
When I turn the key, lights come on as they should. I press the starter and the bike cranks trying to start. If I tap the starter I hear the fuel pump working. I pulled the plugs and checked them against the engine all have good blue spark. I opened the tank to see if the fuel pump had stopped moving fuel, but was still making sound. So I disconected the in tank fuel line before the filter and holding inside the tank cranked the engine. Fuel shot out of the tube at a very high rate. At this point my friend pulled out starting fluid since we had confirmed spark and airflow. Spraying starting fluid into airbox resulted in the engine running but only so long as starter fluid was being sprayed. I pulled the plugs again to check for spray this time and found that the injectors were not spraying. I am new to the bike and am unfamiliar with the path between the fuel pump and the injectors. At this point I am riding back with my friend and will bring a trailer to get the bike back. Any suggestions on how to get it running or what the problem could be would be great.

P.s. sorry for the long post, but I wanted to outline the whole process just in case I might have tripped something that could affect the diagnosis.
P.p.s
I didn't have an ampmeter to check the electronics during this time, so I am unaware if this could be an electrical problem.

Can you post up model and year or put in your signature. Ks differ significantly and without knowing the model/year or VIN you will get conflicting answers.

As suggested its most likely to be an electrical issue.

It is a 1985 K100rt Vin:0051738
Does the signature not add when posting from mobile devices?

Your signature didn't come through on the original post.  No bike information was shown.

Point-Seven-five wrote:Can you see fuel returning to the tank when the pump runs?  No returning fuel may indicate a weak pump, and/or a plugged filter.  If fuel comes back to the tank when the pump is running, the chances are good there is fuel in the rail with enough pressure to make the engine run.

Has the big connector on the ECU gotten loose?  That can affect the injector signal.

The fact that the engine has suddenly stopped working tells me that the problem is probably a loose electrical connection.  Along with the big ECU connector, I would check and clean as many connectors as possible, as well as the bike's ground connections at the transmission above the shifter and on the frame backbone under the tank. 

It behooves you to find the problem in case it is a loose connection.  They can create intermittent problems that can make the bike maddingly unreliable.

I will do a thorough electrical cleaning first thing when I get the bike back to the house, thank you for the tips

Point-Seven-five wrote:Your signature didn't come through on the original post.  No bike information was shown.

Sorry, first time posting from the mobile. Must not have checked the signature box.

With me the hosts generously put the signature details in,  after a while it disappeared, and I had to fill it in myself.

Unfortunately the switch from early model to late happened in 1985, I think. I guess yours is the early model, is it?

daveyson wrote:With me the hosts generously put the signature details in,  after a while it disappeared, and I had to fill it in myself.

Unfortunately the switch from early model to late happened in 1985, I think. I guess yours is the early model, is it?

My tank is indeed the early model one.

Put the headlight on.  Does the headlight go out while the start button is pressed?

John A wrote:

daveyson wrote:With me the hosts generously put the signature details in,  after a while it disappeared, and I had to fill it in myself.

Unfortunately the switch from early model to late happened in 1985, I think. I guess yours is the early model, is it?

My tank is indeed the early model one.

I have the early tank on my K100RT. The plug connector front left of the tank gave me trouble and did what yours is doing....then later the fuel injection control unit [FICU] under the seat popped its plug......and also gave same symptoms. Both after I had been at them. The plug at the front of the tank on early tanks is well known for issues and you can improve it by opening out pins. The plug on the FICU, best take out the FICU and clean the pins and pop it back and see if it solves the problem.

Both of those are very easy to do and then at least you have a solid basis for going on to electrical testing after that. All 4 injectors out implies electrical and not an injector issue.

By all lights good you have neutral on?

daveyson wrote:Put the headlight on.  Does the headlight go out while the start button is pressed?

The headlight did stay on while the bike was cranking

92KK 84WW Olaf wrote:

John A wrote:

daveyson wrote:With me the hosts generously put the signature details in,  after a while it disappeared, and I had to fill it in myself.

Unfortunately the switch from early model to late happened in 1985, I think. I guess yours is the early model, is it?

My tank is indeed the early model one.

I have the early tank on my K100RT. The plug connector front left of the tank gave me trouble and did what yours is doing....then later the fuel injection control unit [FICU] under the seat popped its plug......and also gave same symptoms. Both after I had been at them. The plug at the front of the tank on early tanks is well known for issues and you can improve it by opening out pins. The plug on the FICU, best take out the FICU and clean the pins and pop it back and see if it solves the problem.

Both of those are very easy to do and then at least you have a solid basis for going on to electrical testing after that. All 4 injectors out implies electrical and not an injector issue.

By all lights good you have neutral on?

All lights were good and the bike was in neutral. I will start by cleaning those plugs and then work from there. 
Thank you.

John A wrote:The headlight did stay on while the bike was cranking

The headlight should shut off when the engine is being started. It's one of the loads being shed by the load shed relay to shunt power to the starter.

Does the horn work?

If so swap the load shed relay and the horn relay, then your bike might start,  but your horn won't until you replace the relay.  Hopefully, but sometimes a non working load shed is a sign of a poor battery. 

The front middle relay is the load shed,  the front right is the horn. The part numbers are the same so it's safe to swap.

If the horn doesn't work and hasn't been used in years,  do the swap anyway,  as you might have to shake it up a bit.

daveyson wrote:Does the horn work?

If so swap the load shed relay and the horn relay, then your bike might start,  but you horn won't until you replace the relay.  Hopefully, but sometimes a non working load shed is a sign of a poor battery. 

The front middle relay is the load shed,  the front right is the horn. The part numbers are the same so it's safe to swap.

If the horn doesn't work and hasn't been used in years,  do the swap anyway,  as you might have to shake it up a bit.

The horn does work. I will swap the relays to test it. I'll also clean all the connectors with some contact cleaner and see if that helps a bit. 
Thanks for the tip

I'll be glad if it's the solution as its an easy fix. Cleaning connections helps,  less heat, less power loss,  less stress.

This thread has given me the idea to add late model to my signature,  its much like yours, time wise. 

 Strangely, I like reading about mechanical problems on the net, I'm not learning anything about it on my brick, as it hasn't given me one spot of bother.  (so far) 

By  the way,  if the horn doesn't work after the swap,  hold the relay two foot above a concrete path,  let It go,  pick it up,  and try it again.

My bike does this about once a year, under your seat there is a electrical box, unplug the main connecter, then plug back in, will start right up. Mine does, Good luck with this, my first day on here,

HI all,

Thank you for all the help and suggestions on how to fix the problem. When I got back to my bike I unplugged the computer under the seat and a few other connections, cleaning them and plugging them back in. After that, the bike purred to life on the first crank. I ended up pulling most of the electrical connections once I got back to my garage, giving them a quick shot of contact cleaner and a good rub. I am now enjoying my k100 again. I am also planning on sometime in the next 2 weeks pulling the rest of the connections to see how they are doing and cleaning them all anyway. Probably will add it to my yearly maintenance plan at this point. 

Once again, Thank you for all helpful suggestions on diagnosing my problem.