Took my '85 K100RT out for inspection today.  Less than 17k miles on it, was running perfectly yesterday, and then ran perfectly out to the inspection shop.  I was telling a guy there how it ran like a new bike, etc.  Passes the inspection.  I go to start it, fires for a second and dies.  Repeat.  Repeat.  Then I realize I'm not hearing the fuel pump running after the starter button is let off.  Pull the hose off the fuel rail, no pressure or spray when I crank.

My wife has to come out and pick me up, then I have to get my trailer and go get the stupid thing.  I have made no effort to diagnose other than disconnect/reconnect the tank connector to no avail.  I can hear the relay clicking.

I'm just pissed and frustrated right now and needed to vent!

swamp2 wrote:Took my '85 K100RT out for inspection today.  Less than 17k miles on it, was running perfectly yesterday, and then ran perfectly out to the inspection shop.  I was telling a guy there how it ran like a new bike, etc.  Passes the inspection.  I go to start it, fires for a second and dies.  Repeat.  Repeat.  Then I realize I'm not hearing the fuel pump running after the starter button is let off.  Pull the hose off the fuel rail, no pressure or spray when I crank.

My wife has to come out and pick me up, then I have to get my trailer and go get the stupid thing.  I have made no effort to diagnose other than disconnect/reconnect the tank connector to no avail.  I can hear the relay clicking.

I'm just pissed and frustrated right now and needed to vent!

Before taking a sledge hammer on the pump, just disconnect the pug under the tank, clean it and reconnect.

Crazy Frog wrote:

Before taking a sledge hammer on the pump, just disconnect the pug under the tank, clean it and reconnect.

Yeah, I did that.  No satisfaction...

Do you get any power at the plug under the tank(purple and grey wire)?

Can you say with certainty which relay you heard clicking? Just curious because the fact you hear a click says your starter button is doing something and the known weak points are

the plug connector into the fuel tank, look inside it and adjust the pins to make a tight connection
the plug connector into the fuel injection control unit under the seat
battery earth to the lug on the gear box not being a good earth [also the earths under the fuel tank].
battery connections
battery itself being discharged...have heard of ignition being left on at some of these inspections so not enough to power the bike after and all you get is the starter relay clicking
break in wire between fuel tank and

By the sound of it your fuel pump is not getting any power either bad supply in or no earth allowing it to ground out.

I am yet to try this BUT. met a K100 owner several years ago who had ditched the internal fuel pump and filter arrangement for an external pump and filter. He did some drawings and there are some obvious advantages such as easy accessibility, better visibility of these components and a small increase in tank fuel capacity. His drawing of the location of the external pump shows it mounted to the V shaped part of the frame proximate to where the battery is located. Although some purists may shudder, the fitting of a Lithium battery provides extra necessary space for fitment. I have a 1997 Moto Guzzi Daytona RS (Fuel Injected - similar pressures in the injection system) and Guzzi built them in the factory with an external fuel pump and filter - a delight to work on.
I am giving serious thought to trailing an external fuel pump and filter mod on my 1983 K100 for these reasons.

Nest time you try it, something like this.

I had exactly the same problem, start and then died.

When you try again, hold the start button down and if it stays running then its a good sign its not the fuel pump.

The pump gets signal via 2 sources and one is the start button. But when the engine fires it gets its signal via the Hall Effect Sensors [HES] at the front of the engine. If it stays running while you are holding the start button then you know the fuel pump circuit is good and will stay running provided it has power.

Now have a look at your FICU under the seat and the plug into it. In my case this connection was the problem, due to a small crack on the clip that held the plug into the FICU. I did take it off to clean the connections and it was only on the second occasion I found the little crack. For the time I just swapped it with the one from my LT and glued the crack leaving it to sure.

If when you hold the start button down the pump stays running and the bike cuts out then I would be looking at a loss of pressure inside the tank. In that case open the tank and look in as you fire it up. You should see the return fuel coming back to the tank. See where its bubbling because a pump working means the pressure must go somewhere.

redrockmania wrote: I have a 1997 Moto Guzzi Daytona RS (Fuel Injected - similar pressures in the injection system) and Guzzi built them in the factory with an external fuel pump and filter - a delight to work on.

[off topic] Ooo... I remember thrashing the nuts off the 'B' version of the Daytona in mid '96 for one of the UK bike mags (okay, so it was supposed to be a 'road test'). It hit 250kph (134mph) and was still accelerating when I ran out of road. [/off topic].

If  you do fit an external pump then don't forget that the pickup inside the tank will need to be modified so as to get all the fuel and have a filter before the pump. A pre pump filter will have to be a good one as an 8 micron particle will jamb the pump.

I'm looking at the voltage between the green/white and brown wires on the 4 position connector.  When I press the starter button, I get voltage.  When I release the button, the voltage persists for a second or 2, then goes away coincident with the clicking of the relay.  So it looks to me that everything is ok up to the fuel tank.

When I said it started before after the inspection, I guess it wasn't really running so much as burning off the bit of residual fuel in the rail.

It's a new day, so my emotions have calmed down a bit, but I'm still more than slightly annoyed as I'm also in the process of replacing every single part inside the gas tank of a dead K100LT.  Not a cheap proposition! 2 of my 4 K bikes are currently dead with similar ailments.

Well, I'll be a son of a b.... Was looking at the connector on the harness side... the sockets looked ok, but decided to mash the side of the sockets in a bit to force better contact... reconnect, push the button, hear the happy whine and she starts right up!

I'm happy and all, but WTF!

When you press the starter button you get voltage. Correct.

When you press the starter button you heard the pump run. Also correct.

When you release the start button the power supply from it dies in 1-2 seconds. Also correct.

But when the engine actually fires the pump connector should still have power but it does not get its signal from the same place. The signal for running the fuel pump when the engine is running is coming from the HES. You need to be sure this signal is also giving power to the fuel tank connector.

The short but cruel test I have with my BMW colleague here is to keep the finger on the start button for an extra 5-10 seconds after the engine fires. If it stays running ok the 95% [not 100%] assumption is that the in tank part is working and to look outside the tank. There are instances on the forum of the electrical boxes pin connectors needing cleaning and also broken wires into the FICE under the seat causing this.

You have a number of Ks so one at a time swap an FICU and an ICU [at the headstock] and see if you get a change.

In both cases I had issues like that swapping these boxes cured it. One as I mentioned a hard to see crack in the FICU and the other well I never found out but put it down to dirty pins on the ICU. On my RT the tank plug checked out fine but there was enough wiggle room for it to break the connection and cut he engine. A reworking tightening up of the pins cured it

If you have similar tanks try a swap of your tank onto one of the other Ks.

The K tank system does sound a curse but in fact when you get used to it its quite easy to work on.

swamp2 wrote:Well, I'll be a son of a b.... Was looking at the connector on the harness side... the sockets looked ok, but decided to mash the side of the sockets in a bit to force better contact... reconnect, push the button, hear the happy whine and she starts right up!

I'm happy and all, but WTF!

That's worth a $100 contribution to the beer budget! Happy days and good to see it. Even better is that a lot of K issues can be fixed at the roadside if you know the bike well enough.

Hey, Swampster!  Where are you located?  I am about an hour from Ra-Cha-Cha and would be up for a ride to have a beverage and talk bricks.

Point-Seven-five wrote:Hey, Swampster!  Where are you located?  I am about an hour from Ra-Cha-Cha and would be up for a ride to have a beverage and talk bricks.

+ 1 for the forum and how it leads to this. 


A great outcome.

swamp2 wrote:Well, I'll be a son of a b.... Was looking at the connector on the harness side... the sockets looked ok, but decided to mash the side of the sockets in a bit to force better contact... reconnect, push the button, hear the happy whine and she starts right up!

I'm happy and all, but WTF!

Get rid of that pissy little 4 pin connector they are nothing but trouble. I use a 4 terminal 6mm spade connector.

Point-Seven-five wrote:Hey, Swampster!  Where are you located?  I am about an hour from Ra-Cha-Cha and would be up for a ride to have a beverage and talk bricks.

Hey .75, I'm in Penfield, eastern suburb of Rochester.  But yeah, would definitely be up for an outing!  I'm a recently retired old (59) fart so have some flexibility, let me know what might work for you

Steve

RicK G wrote:

Get rid of that pissy little 4 pin connector they are nothing but trouble. I use a 4 terminal 6mm spade connector.

I was thinking the same thing earlier today - it's a pretty wimpy little connector given the critical nature of the electrons that need to pass through it.  I will likely try to find a suitable more robust alternative.

Grrr! Stopped working again!!!! Hadn't used it for a couple weeks, went to ride it today and she wouldn't start.  The familiar lack of fuel pump noise after releasing the starter button.  So I connect/reconnect the 4 pin a few times, mash the sockets a little more - nothing.  Finally cut the connector out of the circuit and hard wire it (ok, with wire nuts...) - still nothing.  Direct connect the fuel pump wires to the battery - still nothing.  So it seems like my fuel pump bit the dust?  Before when it came back after fiddling with the connector, I guess that was just coincidence?

I still need to check that the +12v is actually making it to the fuel pump in the tank - I realize that can be an issue as well...  Just was too annoyed at the moment to drain a nearly full tank of gas to get at it...

:hp:While we are on the subject of Fuel pumps......I have been looking on ebay at 38mm Bosch for AU$57......a 36mm Kemso for AU$40. What is the verdict on what is best to replace the original with?  There is also a Denso and a VDO for around AU$70.

Get a VL Commodore pump 6 or V6 they are right size etc

RicK G wrote:

swamp2 wrote:Well, I'll be a son of a b.... Was looking at the connector on the harness side... the sockets looked ok, but decided to mash the side of the sockets in a bit to force better contact... reconnect, push the button, hear the happy whine and she starts right up!

I'm happy and all, but WTF!

Get rid of that pissy little 4 pin connector they are nothing but trouble. I use a 4 terminal 6mm spade connector.

Or use a flat trailer wire connector - the colors even work:

RicK G wrote:Get a VL Commodore pump 6 or V6 they are right size etc

Thanks for that Rick G