Poor running after fuel pump change - EV

Hi everyone,

In some ways this is a continuation of my “Strange whining noise” thread. The noise was traced to the fuel pump which I have now replaced. However, the bike now runs extremely poorly and is in fact quite dangerous to ride. Symptoms are:-

  1. Bike fires on the button but I have to stay hard on the throttle to keep it from dying immediately.
  2. With the fast idle lever closed the idle is extremely slow and this leads to stalls on the road. I had to run with the lever open all the time and it wasn’t much better.
  3. The engine is extremely “lumpy”.
  4. Throttle response is strange. Initially as the throttle is opened nothing much happens and the engine seems to stutter. Then it suddenly catches and it is like hitting the power band on a two stroke with the bike accelerating much harder than intended. Rolling off the throttle causes the revs to drop as if you had snapped the throttle closed and the resulting engine braking almost had me over the bars. I was basically pogoing down the road. If the old bill had seen it they would have arrested me (when they stopped laughing).

The bike was running fine on the old (whining) fuel pump and I have replaced it with an identical Bosch unit. During installation I removed the ECU from the frame (but didn’t disconnect any wires) and removed the battery. Once the pump was in I replaced the battery and ran it with the ECU dangling so I could get a good view of the fuel connection. The bike is not leaking fuel. I then reattached the ECU and put the side panel back on, So, I have replaced a whining bike with a poor running bike.

Any ideas? I am getting a little frustrated as I would just like a weekend where I could ride the bike rather than spannering it.


Sorry Richard hadn’t picked up on the other thread
Both symptom could be attributable to an air lock/leak.
With the EV it has been a process of running the bike and checking/tightening all clamps even if they don’t leak fuel.
Sorry if this is old news
Best of luck

Thanks Steve,

Tightening clamps on fuel unions is preferable to replacing the ECU. I only undid the lines to each end of the pump so I will start with these. I was wary of over tightening (one end of the pump has a thin walled aluminium pipe and the other end a plastic pipe) so I can still tighten quite a bit more.

Cheers, Richard

Are you certain you didn’t dislodge any connections when you dropped the ECU?

sounds as though something on the electronic fuel injection (efi) is not happy. If you manage to get the wrong polarity on the battery terminals whist removing/refitting you could have damaged the ecu but as Brian says check the connection to ecu is fully home. Good luck!

Make sure wiring to and from the TPS is sound, also the new pump. With the engine off, check for smooth movement of the throttle body linkage.

I’m inclined to the electrical fault. ECU and battery out to change the fuel pump?

In addition the all of the above, a loose or damaged relay can give similar symptoms. Something similar happened to me when I was in Mid Wales on my V11, and I noticed that the fuel pump relay was not fully seated in it’s base. Easy thing to check first.

Earthing issue.

I suspect a bad connection I would chack all and any connectors and any that were or could have been disturbed, check earth Not sure about YOUR ECU but on the V11 it certainly needs to be bolted to the frame and earthed before starting the bike…

During installation I removed the ECU from the frame (but didn’t disconnect any wires) and removed the battery. Once the pump was in I replaced the battery and ran it with the ECU dangling so I could get a good view of the fuel connection.Oh dear, hope that’s not the cause.

Maybe a silly question, but is pump working properly. Is there a way to test this (general open question for all readers). It sounds a bit like blocked fuel filter, have had this happen on carbed vehicles, starts and idles OK, but cuts out when you want it to go. Not exactly the same I know but.

Thanks for all the ideas boys. I could easily have dislodged a wire on the ECU so will check this. I am absolutely sure that I did not reverse the polarity at any time (this is pretty much impossible on my bike as if I turned the battery around the leads would not then reach over to attach to the wrong terminals). The ECU has a separate earth lead which was why I assumed that I could run the bike with ECU not earthed through the frame so I am hoping that I haven’t b!ggered it. I know that coincidences do happen but tend to believe that, in a case like this, the problem must lie in something I touched so I will start with checking the ECU leads and fuel unions before moving on to things like the relays. I am assuming the new pump is working due to the fact that fuel is reaching the engine. Fuel filter is new and was not causing any problems prior to the fuel pump change.

Never assume, it is not sufficient that petrol is ‘reaching the engine’ it must be at the correct pressure. Also does it not circulate continuously back to tank via the pressure regulator valve (somebody [?])

Did you change the filter as well?

Hi everyone, Yes filter is new. I will run it with the fuel filler cap of to check that fuel is circulating back to the tank. Yours, Richard

Hopefully it is something disloged worst is put old pump back If you get the whirring but fuelling is OK then suspect new pump.

If you get crap fuelling suspect a wire disloged.

I would visually go over it with a very close eye.

When i had had “new” faults after fixing summat 99/100 I have missed summat.

Best one was Annies Virago last year new fuel pump all back ign on …pop fuse blows. I had trapped the very edge of a wire in a panel causing a short… blew 4 fuses before I isolated it and fixed it…dohhhh

Take your tiem buddy go through it, do NOT assume something is ok check EVERYTHING you touched. I am pretty sure you will find the problem.

By the way ther IS enough fuel in the tank yeh?

It sounds stupid but I do know someone who called the AA when their car would not start, he did a couple of checks then went to his van pulled a 1 gallon can threw it in and … click whirrr burble burble, the lady SAID she had put a gallon in that morning…then drove a 3500 V8 15 miles home…yep it was empty …lol

I would visually go over it with a very closed eye

Lol, OK sorry, I misread it but it made me laugh. Like the nonsense rhyme that starts;

“One fine day in the middle of the night, two dead men got up to fight …”

Back to back they faced each other… When something goes wrong immediately after work has been done, always suspect something you did caused it.Very occasionally it might be something unrelated, but not often.

Drew their swords and shot each other!

stop it