Air in fuel line??

[Pagman]

I finally customized my 86 k100. It's repainted, new badges, dual headlights, all together, etc. However, now that it's back together, it doesn't want to start. The electric starter and the battery are fine. The main reason is because gas isn't flowing through the gas line. I tried sucking it through by mouth but no banana. I've never had a problem with the fuel pump. However, when the tank was off, I did try to start the bike thinking i would eliminate any remaining gas. The thing is, i know nothing about fuel injectors! With the tank off on a carb based bike, you would run the bike until the remaining gas depletes from the carb. I'm being told that by starting the K with the tank off, I might have put air into the fuel lines being that it's fuel injected. Is this true? If so, how do I bleed it? Thanks.

PS- I will get pictures up soon!

[frankenduck]

Who is telling you this?

I've brought lots of Ks back to life, replaced fuel injectors, etc... and never had an "air in the fuel lines" problem.

Check the fuel pump fuse - #6.

[Photog]

Any air would get eliminated by the pump either through injectors or the return line. Did you also check that the harness to the tank is plugged in?

[Pagman]

Any air would get eliminated by the pump either through injectors or the return line. Did you also check that the harness to the tank is plugged in?

Yeah, everything is connected.

[Pagman]

Who is telling you this?

I've brought lots of Ks back to life, replaced fuel injectors, etc... and never had an "air in the fuel lines" problem.

Check the fuel pump fuse - #6.

I think my brother guessed on this one. My Kraftstoffp fuse is good, so are the rest.

[DRxBMW]

Who is telling you this?

I've brought lots of Ks back to life, replaced fuel injectors, etc... and never had an "air in the fuel lines" problem.

Check the fuel pump fuse - #6.

I think my brother guessed on this one. My Kraftstoffp fuse is good, so are the rest.

I second, that air in the fuel line is  :cowpoop:

[Inge K.]

Do you hear that the fuel pump is starting, when you push the starter button?

Inge K.

[Pagman]

Do you hear that the fuel pump is starting, when you push the starter button?

Inge K.

How am i supposed to identify the sound of the fuel pump? They are normally quiet on other bikes. When i hit the starter (with choke), the igniting can be heard but the engine wont start. I have an external transparent fuel filter on the fuel line that comes off the left side of the tank. When I turn the key, the bike wants to start but the fuel filter stays bone dry. Normally, this will fill with gas but this time it wont. This is my problem... it's not getting gas. All i did was take the tank off to repaint it. What could I have done wrong??

By the way, everything is reconnected. The two fuel lines on the left and the fuel injector connector on the right.

[frankenduck]

Put your ear to the left middle of the tank to hear the fuel pump when pressing the starter button.  If the fuel pump is working then you'll hear it.

K bike fuel filters reside inside the tank so whatever external fuel filter you have is some kluge done by a previous owner.  It sounds like it's plastic if you can see through it.  I wouldn't recommend using a plastic fuel filter on a pressurized fuel injection system - especially if it's external because if it ever bursts you'll be spraying gas on a hot engine block.

What do you mean by you can hear the igniting? :dunno


What fuel injector connector are you talking about?

[mystic red]

The two fuel lines on the left and the fuel injector connector on the right.

That's not a fuel injector connection, it's the power to your fuel pump, sending unit, etc. Check that connection carefully and where the wires go into the tank. If your fuel pump isn't running it is probably a wire or that connection since all you did was take off the tank.

[Pagman]

Put your ear to the left middle of the tank to hear the fuel pump when pressing the starter button.  If the fuel pump is working then you'll hear it.

K bike fuel filters reside inside the tank so whatever external fuel filter you have is some kluge done by a previous owner.  It sounds like it's plastic if you can see through it.  I wouldn't recommend using a plastic fuel filter on a pressurized fuel injection system - especially if it's external because if it ever bursts you'll be spraying gas on a hot engine block.

Um, i actually put that fuel filter there. When i first got the bike, I didn't know there was a fuel filter inside the tank. Being that I had this transparent filter, I was able to detect that fuel wasn't being fed through. It seems pretty stable as it sits in place, though.

What do you mean by you can hear the igniting? :dunno

I must not have the terminology correct. It's the working sound when you hit the start button before the engine turns on. Just like a car... you know, that cranking type sound as you're turning the car key before the engine starts and all the rpms go up. That's what I was referring to as igniting but I guess I was wrong.

What fuel injector connector are you talking about?

Mystic Red clarified that it's the power to the fuel pump sending unit.

[Pagman]

Apparently, I'm experiencing another problem. My battery died for the second time. I just had it charged at auto zone this past saturday to 100% and the dude told me his tester said it was a good battery. When I brought it home that day, I installed the battery and tried starting it. The fuel pump still did not pump the gas through the fuel line after being fully charged. Everything else worked perfectly, inculding the horn. Can it be possible that the "good" battery is losing its charge quickly? I was shocked to see it completely dead for today. I figure I will exchange it anyway since i still have a warranty on it. Is it possible that a weak battery could prevent the fuel pump from pumping? I just want to see if i could nail my problem down to the battery. I hope it is this simple.

[frankenduck]

If the battery has enough juice to have the starter turn the engine then it's got enough juice to run a fuel pump.

If you can't hear the fuel pump when you hit the start button then it's possible that the fuel level sender connector has gone bad and the fuel pump isn't getting power - not unheard of on K bikes.

[Inge K.]

If you can't hear the fuel pump when you hit the start button then it's possible that the fuel level sender connector has gone bad and the fuel pump isn't getting power - not unheard of on K bikes.

+1.

And if you don`t measure any power at the connector.............when starter button is pressed.
Check fuse #6............and if the fuse is powered.......,,,.......when starter button is pressed.

Inge K.

[motodude]

You've received very good advice.

One thing I would add is that you need to hit the starter button momentarily (just a quick second).  Then let off of the starter button (stop turning the engine over).  Then you'll hear the fuel pump.  I will be quite clear that it is the pump and it will run for 2-3 seconds after you let off the starter button.  If you're not hearing that, then the pump is bad or (more likely) it is not getting power.  Others have already indicated what to check/test.

One other thing.  Once you get the pump working, that clear plastic filter (I have a glass one, I've used them on carburated engines and like them--they are NOT for FI engines) will probably explode unless it is rated to at least 36 psi.  For your safety and the safety of others, I would not leave it there.

Tom

[Pagman]

You've received very good advice.

One thing I would add is that you need to hit the starter button momentarily (just a quick second).  Then let off of the starter button (stop turning the engine over).  Then you'll hear the fuel pump.  I will be quite clear that it is the pump and it will run for 2-3 seconds after you let off the starter button.  If you're not hearing that, then the pump is bad or (more likely) it is not getting power.  Others have already indicated what to check/test.

One other thing.  Once you get the pump working, that clear plastic filter (I have a glass one, I've used them on carburated engines and like them--they are NOT for FI engines) will probably explode unless it is rated to at least 36 psi.  For your safety and the safety of others, I would not leave it there.

Tom

Thanks for the advice and sorry for being so late with this reply. I pressed the starter momentarily and listened for the fuel pump. I heard nothing working within 2-3 seconds. This, along with the combination of no fuel running through the external filter (which i will get rid of), should be enough to diagnose my problem. It seems like it's one of two issues, a bad fuel pump or a bad sending unit. But how could either go bad just because i removed the tank to paint it? Anyhow, all fuses are good. Is there a way to check for which one is the culprit?

By the way, I found out why my battery keeps dying. The highbeam indicator stays faintly lit even with the bike shut off. I noticed it at night time. However, this is electrical so it is the least of my problems. As long as my K is running, i could at least take it to a friend to get it checked out.

[Inge K.]

And have you measured if you got power at the connector and the fuse, so far?

Have look in this recent thread, from post #27 and on, it could maybe be to some help.........


Inge K.

[frankenduck]

.... a bad fuel pump or a bad sending unit. But how could either go bad just because i removed the tank to paint it? Anyhow, all fuses are good. Is there a way to check for which one is the culprit?

The part of the sending unit that usually goes bad is the connector so there's a decent possibility that it was on it's last leg when you disconnected/reconnected it to paint the tank.  Push the connector together and wiggle it around to see if that helps.

You can also jump 12V to the smaller terminal and ground to the larger terminal on the fuel pump to test it.

[motodude]

+1 on the connector for the tank.  They've been known to go, "bad".  A lot more often than the sending unit in the tank.

[Rick G]

I have had to fix that connector on all 3 Ks I have.  On the K100 I could not get it to work properly and ended up getting a new 4 pin connector from the Auto shop.

[motodude]

I have had to fix that connector on all 3 Ks I have.  On the K100 I could not get it to work properly and ended up getting a new 4 pin connector from the Auto shop.

I have used frankenduck's recommendation of the 4-pin flat trailer light connector with very good results.  Being flat, it fits nicely between the under-seat compartment and the relay box.

Tom