Won't start

[rlusher]

Hello all. I have been posting a little about a fuel pump issue. I just replaced a fuel pump/filter. I reconnected all the hoses, first marking them, then double-checking them against BMW diagrams to make sure they were properly connected. The fuel pump spins up properly, but the bike won't start. I am pretty confident the pump was bad because the old one would not spin up properly at start. Any thoughts? Thanks!

[Kathy R]

Best of luck

 

Can you add your bike info to your profile and or this post.

[dirtrider]

Morning rlusher

 

A couple of thoughts.

 

First off, is the pump spinning in the correct direction? You talk of re-wiring the pump? Brown wire is the ground side so be sure pump is wired correctly & correct polarity.

 

If it won't start then you have to determine if your problem is lack of fuel, or lack of spark, or lack of compassion, or lack of air flow.

 

If your engine has enough airflow, with proper fueling, with enough compression, & is being sparked properly at the correct spark timing then it will start. So you need to check & determine what you don't have.

 

Do you have a nice bluish spark that will jump a 3/16" electrode gap with ease? If not then look into HES or other sparking issues.

 

Do you have a enough fuel pressure to have flow out of a disconnected fuel return line? If not look into pump issues, or hose connections loose, or cracked pressure hose leaking inside the tank.

 

Do you have 12v power TO the fuel injectors & if so does the Motronic make the injectors pulse during engine cranking? (remove a fuel injector & point it into a jar with wiring & fuel line hooked up then crank engine to see is you get a nice spray mist of fuel as the engine cranks over).

 

About all you can do is verify each & every system is working properly starting with spark then checking for fuel out of one of the injectors.

 

[tallman]

Are you getting fuel at the injector?

 

What happens when you try to start it?

Nothing?

Turns over no start?

[rlusher]

Thanks to all for the quick comments.

 

-Dirtrider. I had not thought of the possibility that the thing could be wired backward. I thought I replaced the wires correctly, but anything is possible at this point. I will double-check.

 

-Tallman. The engine turns like normal, but just does not start.

 

-Kathy. Will add bike info to my profile (99 R1100RT).

 

Other suggestions I would have to refer to a pro as I am not quite that competent.

 

Thanks again.

[SAAB93driver]

Just my 0.02....If you have quick disconnects in the fuel lines make sure they are seated fully. I had the non starting problem once after pulling the tank, drove me crazy, no fuel to the injectors. I finally found out the feed line QD wasn't fully clicked in place even though it looked like it at first glance.

[roger 04 rt]

Just my 0.02....If you have quick disconnects in the fuel lines make sure they are seated fully. I had the non starting problem once after pulling the tank, drove me crazy, no fuel to the injectors. I finally found out the feed line QD wasn't fully clicked in place even though it looked like it at first glance.

 

Since I put the metal QDs on, exactly that has happened a few times. They work so well and the plunger isn't shielded that if the plunger contacts even a tie wrap they will open. It can be hard to see it visually.

[flars]

And, of course, there is the ever popular scenario where the hose gets blown off the pump.

[roger 04 rt]

And the scenario where after replacing the filter, a hose splits--like mine did.

[dan cata]

And, of course, there is the ever popular scenario where the hose gets blown off the pump.

 

I had that once. The hose came off the fuel pump inside the tank. Took me ~ 4 hours to find the problem...

 

Thanks,

Dan Cata

[David R]

Give the bike a shot of starting fluid. See if it fires. If it does, you are on the right track.

 

Fuel pump runs, so you got the wiring right, next you need to check for pressure.

 

david

[eddd]

...Fuel pump runs, so you got the wiring right...

 

david

 

If you wire a DC motor wrong (reversed polarity) the pump will run, but it will run in the opposite direction.

[dirtrider]

Morning eddd

 

Just for reference--

 

Not all DC motors will run backwards if wired backwards, just DC motors with permanent (fixed) field magnets & some special use DC motors.

 

DC motors (like a lot of starter motors) will always run the same direction regardless of polarity because the fields are not fixed polarity permanent magnets but instead use wire wound electro-magnets.

 

On electro-magnet field DC motors (like most starter motors) the field coils ALSO reverse magnetism when the polarity is reversed so the armature to field attraction/repulsion remains the same direction regardless of polarity.

 

On (most) permanent (fixed) magnet DC motors (like a lot of fuel pumps) only the armature changes polarity so they do run backwards when the DC power feeding them is reversed.

 

Not being critical just trying to educate future readers.

 

[tallman]

DR,

 

If I switch my wheels front to back and vv, will I have reverse?

 

Thanks for the good synopsis.

[David R]

Tallman, will you have front wheel drive? Op still needs to check for pressure.

[tallman]

[rlusher]

Thanks all for the help. It is Saturday, so my hunt for the problem continues using the great advice you have all given. Thanks again!

 

-Rick

[David R]

Whaddyagot?

 

We all want to know.

[rlusher]

OK. Thanks again for the help. I greatly appreciate it. I am a very novice mechanic, but am technically inclined enough to do some of this myself. The advice on this forum is very valuable.

 

Thanks, too, D.R. for asking for the update.

 

I took the fuel pump out again and checked the connections. Sure enough, the wires were backward. Some of the posts suggest this may not be an issue, but I switched them anyway. Having the hoses disconnected, I stuck the pump down inside the tank into the ~2 gallons of fuel, and checked it by turning the key on/kill switch run, and it ran, spiting fuel from somewhere (I only let it run for a second, so am not sure where it came from). Is this a good sign? My thought was yes. I cannot reassemble the tank until the O-ring dries out (made the mistake of not keeping the old one) so will not know for sure for a couple of days (at least that is how long I have heard it takes to dry the ring).

 

Thoughts? Are there other ways I can check it for sure before reassembling the tank? if not, I'll just wait it out.

 

Thanks again!