Sorry in advance for the ignorance...

I just bought a 2001 f4i and it ran great for the first couple weeks, but I'm having some problems already. I feel like it might be the fuel pressure regulator just by reading around a little bit, but I'll give you my symptoms to see if anyone else knows what I should do to start diagnosing the problem for real.

Obviously when you turn the ignition on and the engine kill switch is switched to on, the fuel pump (?)/pressure regulator (?)/ whatever that initial sound is made by that comes on before you can start the engine needs to turn on. Sometimes it does, and sometimes it does not. When it doesn't come on, the engine won't start. What part is this and does this mean it needs to be replaced or is there a connection or something that may be messed up causing it to only work part of the time?

The next symptom (I'm sure related in some way) is that the engine when riding, particularly below 5k rpm but also when getting on it hard above that, stutters pretty bad sometimes. It feels like the engine starts to die, then comes back to life and makes the bike take off. I keep worrying that this could happen on a sharp turn and cause some more serious problems...

Anyway, any idea as to what the problem could be? Sorry to be a PITA but if youre going to use abbreviations for different parts and components could you explain what they mean too? Thanks for being patient let me know if you need more details.

Max

 

Anyone? I could really use some help guys. Thanks!

 

that's your fuel pump that makes the sound you speak of, it's called priming

for it to work sometimes and not others could be the fuel pump going bad or could be something as simple as a loose connection
does the starter turn over if the fuel pump does not prime?
if it doesn't maybe you have a bad engine stop switch or a bad connection associated with it

also, did the shuddering feeling you mentioned begin at the same time as the other problem?

 

Pretty sure that's ur problem. Exact same thing happened to me. Tell ya why:

1) fuel pump doesn't prime. When fuel pump doesn't prime the engine doesn't start. This is likely because your front harness is starting to come lose, or your front harness isn't grounding correctly. When this happens, your ECU loses touch with your bank angle sensor. When the ECU loses touch with your bank angle sensor, it'll kill power to the fuel pump.

2) Hitting bumps and things can cause it to temporary lose connection, causing power loss and sudden power surges

3) Kick stand switch, clutch switch etc that everyone tells you to check will not kill your fuel pump, so rule those out.

4) that'll be $5 if i'm right.

I took my fairing off in the picture above. you don't have to do that. You can reach it without taking anything apart. lube it up with dielectric grease and see if it comes back. if it doesn't, $5

 

Make sure you measure the voltage of the connector to your fuel pump. When you turn on the ignition kill switch, it should have at 12 to 13.8 Volts DC going to it, regardless of whether or not you hear the fuel pump 'priming'. I had replaced my fuel pump. It had to voltage going to it, but it would not prime, but sometimes make a nocking noise (probably from the bike sitting too long/ the fuel turns to gunk and ruins the fuel pump).

 

Ok, thanks for clearing that up about what the part even was. Yes the shuddering started at the same time (it only happens when the fuel pump problem is happening) but I don't think its been directly related to going over bumps (although it definitely seems like it could be if a loose connection is the problem). As soon as it stops raining for a few minutes I'll be out there checking it all out. I'm almost positive its not the engine stop switch itself thats faulty, as it always turns over even when it does not prime. Thanks guys and I'll check in when I get out there to inspect the connections and everything.

 

Stopped raining for a few minutes and decided to at least go take a look... Ended up being a project but hopefully all will be well now.

That front wiring harness that you showed me had more problems than I even knew. One of the previous owners had ghetto spliced some wires into two of the wires leading into that harness- a red one with a white stripe and a green one. Not sure what the jumper wires were for, but they werent even connected to anything anymore so i removed them. The original wires themselves were basically destroyed, only a few threads left before they were completely disconnected. I cut each wire, cleaned up the split ends, and soldered them back together then wrapped them up nicely with liquid electrical tape. After that I ended up unhooking the harness itself and cleaning the leads in there for good measure (they looked like they had some corrosion on them anyway). Anyway, put everything back together and the fuel pump came right on when I went to start the bike, so hopefully everything is fine. I didn't even get to take it around the block because as soon as i started the bike it started to rain. Anyway I'll let everyone know how it goes after the weather gets nice. Thanks for the help!

 

Took the bike out for a ride- ran great on the way out. Stopped at a store, came back out, went to start the bike and the pump wouldn't come on. After about 5 minutes of trying it finally came on, and the bike rode like crap all the way home doing the same thing it used to do with losing power than coming back on.

 

Having gone through the above, if the bike starts to buck/shudder when you give it gas, you are losing contact somewhere in your circuit.

The first place to check is that your battery leads are properly tightened.

 

Check the battery leads this morning, they were fine. Can anyone tell me or show me pictures of the fuel pump itself? Couldn't the problem in the circuit be directly where it plugs into the fuel pump?