Remove the pump and run it backwards it may have a very small particle stopping it turning.
An 8micron particle can seize a rotor cell pump. If reversing it works renew the pre pump filter and try it again

Can you hear the fuel pump whirring when you press the starter button?  Sometimes the issue is in the  connections in the baseplate of the fuel level sender. I'd try bypassing the fuel level sender and jumping 12V directly to the fuel pump.  Hook some other wires up to it in then then apply 12V to them.  Probably a good idea to avoid causing sparks around gas fumes while doing this.

Probably a good idea to avoid causing sparks around gas fumes while doing this.

+1   There's no roadside assist on the highway to heaven.

we have seen that fuel pump connection (below the tank on the right hand side and under the side cover ) become lossy ....ie the connections become faulty ..sometimes the socket part spreads or becomes corroded ...many have crimped the socket part  slightly to provide a better connection to the pump inside the tank ...
perhaps this is a contributing issue ...and no where near a rare event
all the usual suggestions apply ...clean both sides of the connector with a good cleaning agent ...and not talking about anything with ammonia or similar ...look up "deoxit"  a friendly substance for such jobs

also do the fuse carriers and fuses ,,whilst your there

these connections are old on all the bikes and a slight bit of intermittency can promote carboning up of the connections

so a bit of regular maintenance is always a plus

cheers !

When you say you tested the fuses did you use a meter. We have see a few recently that have gone open circuit due to age and still look good.

Owning a K that is 20 odd years old does sometimes become a PITA but think of the pain in the wallet if you buy a new bike.

The fuel pump should turn on when you turn the key on and run for 1.5 seconds being a 16v engine. (Duck was referring to the 8v engines) If that doesn't happen then you need to fix that without going further and the first place to look is that mongrel connector Charlie is telling you about. Mine gave me so much grief that I went to the auto store and bought a new 4 pin connector and replaced the plug and socket (it doesn't have to look the same, a white one with the flat spade type push in connectors are fine) and its been bliss now for 2 years with regards to that. The bliss has not extended to many other places.

Is the fuel filter new?  A blocked filter could prevent the flow of gas.

+1 on the fuel filter. IIWM, I'd pull the flapper, and turn the key to determine if the fuel pump is pressurizing the system. then replace the fuel filter and inspect the strainer on the pickup.

Thanks for all the suggestions really appreciate it. This morning I replaced the fuel filter, then checked the basket on the fuel pump, no goop inside. So I checked the lines to see if there were any obstructions, they're good. Then I unhooked the tank like I did before, ran power direct from the battery to the input connector, and I didn't blow up so I knew that was a good sign, and also the pump started. 

So I reversed polarity for posterity, and tried it again and it would not go, so I repeated the process and it started going again. Guess I got rid of whatever crap was in there. Then I plugged in the FPR and a fuel pressure gauge. When I turned the pump on again there was no gas coming out the brand new FPR, first with 50lbs then even 100lbs of pressure - I ran it longer so see if I was imagining it. Guys, am I missing something? Isn't there supposed to be a bit of gas coming out of the FPR? Here's my setup:



I have a backup fuel pump that I would need to MacGyver with some extra rubber to fit into the BMW sleeve. It's a Facet-Purolator FEP 20-82, cheaper alternative for all K Bikes. Anyway it's on standby if this thing is pooched. Thanks again.

sounds like that could be a real show stopper

charlie99 wrote:sounds like that could be a real show stopper

Can you elaborate?

TSBT, 

It's not obvious to me from the photo above but, in your test setup, which direction are you expecting the gas to flow?  Is it from the tank, past the pressure gauge, into the FPR and out towards the red gas can?

What do you mean gas coming out of the FPR?

Here's the direction of flow: Pump->Filter->Fuel Rail->FPR->Back To Tank

So, yes, if the line from the FPR to the tank is disconnected that should have fuel coming out of it if the fuel system is working properly.

duck wrote:Here's the direction of flow: Pump->Filter->Fuel Rail->FPR->Back To Tank

Okay I must be high on gas fumes, confirm my logic: of the two lines coming out of the gas tank, the first one (towards the front of the tank) is the return which takes the line from the FPR. The second line sends gas to the fuel rail. Something tells me I may have had the two mixed up, in which case you have solved my dilemma! and I am clearly still high from two days of high octane fumes  

robmack wrote:which direction are you expecting the gas to flow?  Is it from the tank, past the pressure gauge, into the FPR and out towards the red gas can?

I think I mixed up the fuel lines where they go into the tank, as per Duck's description of fuel flow: gas pumps directly into the rear of the fuel rail, goes to the front of the fuel rail where the hose takes it to the FPR and around to the return line in the tank. I think I had the lines mixed up at the tank which is embarrassing. In which case I can't wait to put it back together and start it up!

Rear pipe to fuel rail, front to FPR

duck wrote:Rear pipe to fuel rail, front to FPR

Thanks Duck. I'll have a ceremonial large beer in your honour later if she starts.

As much as I want to say I'm having a beer it didn't start, the pump didn't run. I'm thinking the problem has to be the Fuel Sender Relay, once I find it. When I checked the plug to the tank earlier however I was getting power which is weird...I'm not sure.

I'll add I took Charlie99s suggestion and cleaned the connector, also wiggled it a bunch. Maybe I need a new connector. The whole thing is fishy,

TSBT wrote:I'm thinking the problem has to be the Fuel Sender Relay, once I find it.

Have you checked your sidestand switch? If the sidestand is down, or you got a malfunctioning switch......it would prevent the fuel pump to run.

First check if you side stand is down. LOL.

What he said.  Find the connector (it comes up out of the right peg plate with the brake switch wiring), unplug it and short the connectors on the wiring harness side.

I have all of mine disabled so it usually never occurs to me as something to troubleshoot.

Also, if you find that it's that side stand tang not pushing the switch all of the way in than an easy fix is to put a short piece of vacuum hose over the tang.

When I shorted the one on my LT I hooked the switch up to an idiot LED in the dash to remind if I left the side stand down.  It started coming on every now and then while I was riding and that's how I fixed the intermittent switch problem. Has worked great for the last six years.

Sorry guys think I posted a new topic when I should have hit reply to this thread!

Thanks for the KBIKE article always a good refresher. Fired up the multimeter and I'm getting a .53 multimeter reading off the Tank plug.



Then I tried swapping out the Fuel Pump Relay with the one next to it. Same reading. Checked all the fuses they're all getting 13.8 with the ignition on. bent the 4 prongs in the tank plug a bit, to see if I can get a better connection. 

All roads are leading to, no whirrly sound from the pump unless I do a direct jump from the battery to the tank. So I guess it's a hunt for the loose connection. Still haven't clipped the two wires on the sidestand plug and tapped them together. So that could be an issue, will do that later.

How about we ask Mr Moderator to combine them. I think that's the first time I've called him mister 

I had the bike on the road today, zipping around town doing a shakedown. How did I get it running? With the help of Robmack, he reached out and asked if I could use some help because we live in the same city! I was thrilled and took him up on his offer. The next day he rode over bringing his laptop, filled to the brim with schematics and his Fluke Multimeter. With this kind of ammo I was certain we were going to fix this.

We traced wires, tested plugs, fuses, relays, and we also checked the connection at the side-stand, suggested by Inge and Duck as a usual suspect, and I have to say I feel pretty stupid. I installed it with the tang in FRONT instead of behind the rotator that opens and closes the circuit. 

When we discovered this we were both pretty excited, and I felt pretty stupid, it's amazing how something so dead simple got overlooked. But thanks to Robmack I've got my bike back. Cheers, you made my week! 

And thanks again for everyone's help really appreciate all the suggestions I've learned a ton.

Now that the bike is running, hopefully Robmack and I can plan ride sometime, that would be fun. 

Proud to say this K100 case is closed!!!   

yippee !

good onya blokes ...

Hi Chris,

I am glad that your bike is back on the road after too long a hiatus.  I enjoyed the challenge; next one will be that cruise control.  Get in touch if you want me to help.