Cranking but won't start

[didymus]

I know, this wouldn't usually be worth starting a new thread about, but this case is a little different.

My bike died as I was riding it.  I pushed it to the local garage and had them install a new fuel pump.  Rode it home. (This is the short version, that took about a month.) 

I tried to start it a couple of days later and it would crank as usual but wouldn't start.  It was really low on gas, so I put in a couple of gallons.  Still wouldn't run.  I pulled the plugs and checked for spark on the first plug, which looked fine to me.  With some starter fluid in all the cylinders it would start to turn over but then stop.  I could hear that the fuel pump was working so I figured I had some kind of problem with the fuel between the pump and the engine.  I took a look into the tank and I could see that a hose was disconnected, so I slid it onto the nozzle looking thing next to it and figured the problem would be solved. 

Still wouldn't start.  I took the plugs out and tried to get it going with starter fluid 3 or 4 times.  I tried putting a little motor oil into the cylinders.  Nothing.  I took off the gas cap and looked into the tank to make sure that the new pump wasn't just getting power but was actually creating pressure.  It was.  In fact, I could actually see it squirting gas up to the top of the tank... which didn't look right.  So I realized that that loose hose was supposed to go to the fuel pump, not whatever I stuck it on (a little metal tube coming down from the top of the tank just behind the cap).  I attached the hose to the fuel pump where the fuel was squirting out. 

I tried to start it again a few times and eventually got a really loud backfire.  I thanked god that I was still alive but I still couldn't get it to start.  I could smell fuel at the tailpipe.  I took out the plugs and dried them all off.  Tried again but still just got a sputter.  At this point the bike hadn't actually run in a month and I'd been using the starter and probably taxing the battery, so I put it on a tender for a day.  Tired again and it sputtered a bit the first time, but wouldn't quite run.  And that, my friends, is my tale of woe and folly.

So I'm guessing the problem was that the hose from the fuel pump came loose, and that's fixed but I must have done something else to mess it up while I was trying to figure it out.  Is there air in the line from the hose not being attached to the pump?  Is it just flooded?  Did I really messed something up with my screwing up the hose connection?  Or with the backfire, or what?  Maybe an evil spell or hex of some sort? 

Clearly I'm not that good at this, so please try to use small words. 

[Laitch]

I know, this wouldn't usually be worth starting a new thread about, but this case is a little different.

Welcome, didymus.

I don't read anything different about your bike's case than any other of the multitudinous cranks-but-won't-start cases already here. It's virtually an oft-told tale around campfires since the dawn of used K-bike purchases. There's a fault—or faults—somewhere so an orderly investigation must be conducted to find a remedy.

Was the hose you attached to the fuel pump also attached to the fuel filter? Did you disconnect the outlet side of the fuel filter to see if a strong stream of fuel emerged from it? Did you check the clamps of all hoses within the tank for tightness? Do that then report back.

Did you read the No-Start—Slow Start Whackiness guidance in the Repair Guidance section and try the methods appropriate to your bike's condition? Do that then report back.

Post some photos of your bike and tell us how much mileage is on the clock, how long you've owned it and how many miles you've ridden it. Tell us everything that has been done to your bike, using all descriptive words at your command regardless of their length. Many here are eager to help, probably.

[johnny]

greetings...

you gotta do 1 thru 4 at this link... verify and report back here before making another post...

http://www.motobrick.com/index.php/topic,11033.0.html

j o

[paratrooper34]

Don't know if this is the same problem, but I had the same symptoms you have on my '88 K75S.  Mechanic found a loose connection for the fuel pump wiring under the tank (at least this is what they told me anyway).  Since they fixed it, I haven't had a problem.  It's an easy check to see if that is your problem.  Good Luck!

[spoospe]

Going through a similar process myself on an 88 k75s- except I limped it home instead of to a shop.

I'm also uncertain where one of the fuel pump hoses goes. There are two hoses visible when viewing the pump from the top: one goes straight out of the top of the pump back around to the filter, and the other goes through a slot in the whitish yellow plastic of the basket near the base. Should the second wire be submerged or should it be connected to the vent tube sticking downward from behind the tank opening? According to the repair manual, there should be a vent hose going somewhere.

 Second question: is your #6 fuse blowing? I noticed that one blew and another was looking singed.

Battery is trickle charging now, so I have time to think!

Thanks for the "No Start ~ Slow Start ~ Whackness" thread amongst many others, Johnny.

[Laitch]

According to the repair manual, there should be a vent hose going somewhere.

Those pesky vent hoses always seem to be going somewhere. Sometimes though, they aren't even necessary. Try hooking it up according to this diagram from the BMW Repair Manual downloadable from the world famous MOTOBRICK.COM.
 


If your pump's fuse is blowing, your pump, its outlet hose or the fuel filter might be clogged, the pump might be seized, the fuse sockets might be corroded or the wiring from the pump's four-pin under-tank connector might be damaged. Replace the fuses with new fuses of the correct amperage and clean the fuse sockets with emery cloth. Check the condition and connections of the wires from the fuel level sender to the pump. You've already cleaned the 4-pin connector if you've read the No Start guide.

didymus should take note of this. too.

[didymus]

Glad that no one seems to think I messed anything up by connecting the hose to the wrong place.

I doubt it's one of the electrical issues in "No Start ~ Slow Start ~ Whackness".  It'd just be a really odd coincidence for one of those elements to go while I was trying to straighten out a fuel issue, and if the ignition switch were the problem, wouldn't the starter stop cranking?  And if the 4-pin connector was the issue, wouldn't the fuel pump stop working?  All the same, I checked the connections.  They look fine to me but I'm going to get some Deoxit and check all that out and clean it all up anyway because it can't hurt.

Checking the fuel pressure past the filter seems to be the next thing.  It's entirely possible that something got clogged with the installation of the new filter and pump.  Maybe built up pressure from a plug is why the hose popped off.  I got some new clamps, but it seems like a real PITA to get those crimp-style clamps off inside the tank, and I don't know how I'm going to get the new ones on yet because they require a screw driver.  Should I start with the fuel line on the outside and then if it's plugged work my way back?  Can I do that without spraying everything with gas?  I'm thinking of just disconnecting the hose over a bucket and cranking the starter to see what happens?  Too stupid?

[didymus]

For background; I got the bike 5 years ago.  Never had a problem with it not running before.  I've only put a few thousand on it.  The odometer stopped working years ago, around 86k. All stock (jk see pics).  Haven't really done much of anything to it in a long time other than this new fuel pump.  I wish that weren't so true.  I haven't even done an oil change in more than a year.

[rbm]

I see your problem right away.  All the fuel is at the top of the tank and nothing is getting to the injectors.  Invert the pictures and all will be well. :wave:

[didymus]

Good eye, rbm.  I watched the Terminator movies while I was growing up, so I knew I'd be spending my adulthood fighting computers.  I just didn't think it was going to be like this.

[The Mighty Gryphon]

Remove the hose from the rear end of the fuel rail and put it into a 2 liter bottle.  Turn on the key and hit the starter.

Does fuel flow into the bottle???

[didymus]

It's alive!

I took the hose off at the rear end of the fuel rail as suggested.  Total pain BTW.  Cut through the hose with the clamp trying to get that ear clamp off.  When I tried to crank it I didn't get any fuel.  Brilliant.  So it's probably a clogged filter and I have an extra one of those.  But I took off the filter, and still nothing.  I took the hose off the pump right where I'd reattached it when I noticed that the pump was pumping but not connected... nothing.  That was the one thing I thought I knew!  I watched the damn thing spraying fuel before.  But now it didn't even look like it was getting power at all now. 

So I cleaned the connections as suggested, and checked the fuses.  The fuse for the Kraftstoffp was blown.  After a little research, I replaced it with the Standlicht (running lights) fuse, and the pump worked!  The filter is working too because when I put it all back together she's running just fine.  So now I just need a new fuse and a couple of legitimate fuel clamps and I'm good.

Still a little mysterious.  Was the filter clogged and I unclogged it then I took it apart?  When did the fuse blow?  Why are humans externally bisymmetrical but internally asymmetrical?  So many mysteries... 

Thanks, all.

[Andy FitzGibbon]

I used to have problems with my fuel pump fuse blowing in hot weather. This was with a new pump and clean electrical connections. It seems that the temperature of the fuel was the issue... in high ambient temperatures, the fuel would get hot enough to boil in the tank, and the pump (which is cooled by the fuel) would draw enough to overload the fuse. After insulating the underside of the tank and the fuel lines, the problem hasn't returned.

Andy

[didymus]

Good tip.  It has been hot as the red end of hell around here lately.  I was trying to get as little sweat as possible into the gas yesterday.

[spoospe]

Finally got mine back to life. Two weeks ago, I cleaned the tank and replaced the fuel and battery. It ran beautifully for about 20 minutes and died on the road. Turns out the fuel pump had seized. Pulled it out connected it directly to the battery only a *click*. Tried connecting it backward same *click*.

Bought the 52mm duralast from euromotoelectrics for $105 and the fuel pump screen (which FYI is a necessary purchase for the warranty on the pump).

Thanks for advice here.

[didymus]

Hope it works out for you, spoospe.  Mine's having problems again.  I did an oil change and now it's sort of surging and sputtering.  Not idling when I start it without giving it throttle.  But I don't think it was the oil change.  I'm guessing that the gremlin is still in the fuel line somewhere and was just hiding.

[Laitch]

Mine's having problems again.  I did an oil change and now it's sort of surging and sputtering.

Be sure the oil filler cap is tightly closed.

[Laitch]

But I don't think it was the oil change.

When dealing with an unknown cause, the most effective strategy is to keep an open mind to all possibilities.

[didymus]

Good idea.  It's not loose now and that doesn't seem to be it.  But when I had it running just after the oil change I took it off to top off the oil and noticed the engine starting to die, so I put it back right away.  It seemed to keep running fine after that, but the next time I started it was when I started having problems again.  It might have something to do with that.

[didymus]

It's making a nasty sound too:



Any idea what's making that thrumming sound when I give it gas?

[Laitch]

Any idea what's making that thrumming sound when I give it gas?

Don't worry about that sound if you haven't done a tuneup yet—manifold leak check, valve clearance check, air filter cleaning or replacement, spark plugs check or replacement, throttle body balance. You seem to have checked the fuel system and replaced the hoses but I'm uncertain that you performed the fuel volume check Gryph recommended. If all that was good, tuneup is next.

[didymus]

That's all good stuff, but first I need to be able to get it home or to a garage.  Not sure if I should try to ride it like this.  It's not really getting up to highway speeds reliably.
 

[Laitch]

Where are you? Last I saw, it was in a driveway next to a mowed lawn.

[didymus]

That's where I work.  I limped it in on Tuesday and got a ride home.  Bike's still there.

[Laitch]

Visit it to re-clean and reconnect the four-pin fuel pump plug under the tank and the L-Jetronic plug under the seat then take a look around it to be sure the battery terminal connections are good, the battery ground connection on the transmission is clean and tight and nothing else is whack·like the z-tube from crankcase to air box. If you bring a phillips-head screwdriver and appropriately-sized wrenches, you can tighten the fuel pump connections in the tank. After that, have a calzone.
  :yes