Questions regarding fuel injection bits....

Right, I have a few Q's on the subject of fuel injection.. well, some of the gubbins that make it work...

I have a Kwak ZX-6R B1H... and its playing up rather badly at the moment....

at 10,000 rpm, it stutters quite badly...

now, Ive been trying to find the fault for a few days now.. I have two things left.. the camshaft position sensor, and the crankshaft position sensor.

Now, from my extensive googling on the subject.. both are rather important on a fuel injected bike, as it is them that tell the ECU when it can do its stuff...

So, questions.... what effect would either one being iffy have on the bike itself? would they possibly have the above effect of severe stuttering at high RPM ??

cheers for any help.. as it will stop me from pulling most of my hair out!

[Speedy]

Well on cars,The C.P.S. is fitted to tell the E.C.U. when to 'fire' the spark plug,basically like a Contact-breaker set-up (points) on old type ignition system.

When piston is at T.D.C. the sensor triggers the E.C.U. to tell the Ign.Coil to discharge,Causing a spark.

Camshaft position sensor is to tell the E.C.U. when to operate the fuel injectors. This can also be done with Crank sensor,but with V.C.T. (variable cam timing) it isn't accurate enough.

Hope this helps!

[Sid Squid]

Both those sensors are important of course, but - very generally speaking - most of those sort of sensors are inductive, as such it's a coil of wire, so either it works or it don't, this doesn't mean the wiring/connections/bit of the ECU they connect to are perfectly well though.

If it's a high revs problem, I'd look at fuel pressure, so that's pump/relief valve and associated bits.

And, no offence, this does of course assume that all the other checks you have thus far done, were done right, and that there's no other obvious possible troubles ie remaps/Power Commanders/wildly unsuitable exhausts/air filters etc etc.

So its possible that if either went buggered up (as the Kwak has camshaft and camchain position sensors) then that could cause the bike to go rather iffy at higher RPM ? The exact feeling of what the bike does is as if the engine stops for a split second... could that be the effect of the spark plug firing at the wrong position ?

cheers! may have actualy found out my bikes problems now then....

now to pester the mechanics tomorrow!

bikes standard under my ownership.. no power commander fitted, but I cannot guarantee what the previous owner may have done to it.

previous test.. well, check that it wasnt the fuel cap clogged.... took fuel cap appart, cleaned... and also to double check, rode around with cap open.. still problematic! air pressure sensor... changed over sensor with another one in the system (as there are 2 identical ones doing slighttly differnt things on bike) still playing about... fuel pump at start up.. measured amount of fuel coming out of pump when inition turned on.. within tolerance. checked for debris in tank. clean as a whistle. which out of the troubleshooting section of the workshop manual.. leaves just the camshaft and camchain sensors. stick coils have been attacked with a multimeter.. all within tolerance, the camchain sensor was checked, thats within tolerance, but the wiring seems to be shorting out.
the multimeter is returning a value, when it shouldnt be.

So was just wondering what the effect would be of a wrong signal being returned to the ECU by that sensor ?

The bike has been playing up over a long period of time, but is only noticable when going through 10K in a hurry.. and as we are now in better weather, the problem seems to be more apparent, as Im being eager on the throttle for once! dont wanna hit 16K RPM in the winter you know!

I thought it was iffy spark plugs originaly, but changed those, problem was still there... changed oil, vacuumed filter out.. its dirty, but not THAT dirty as to cause problems...

and it only ahppens when the bike is in motion, I can revv the bike like buggery in neutral, nowt happens.

Thiking of it, it did it shortly after I bought it.. but I thought it was hitting the rev limiter.. but now I can look at the rev limiter when its happening, and its no where near the 16K mark.. its roughly at 9500 - 10,000 in all gears...

[Sid Squid]

Originally Posted by valleyboy

So its possible that if either went buggered up (as the Kwak has camshaft and camchain position sensors) then that could cause the bike to go rather iffy at higher RPM ? The exact feeling of what the bike does is as if the engine stops for a split second... could that be the effect of the spark plug firing at the wrong position ?

cheers! may have actualy found out my bikes problems now then....

Doubtful. The crank sensor gives specifics of crank position and importantly speed but not firing point, the ignition timing map/curve is built into the electronics, most car motors have knock sensors too, this gives very precise ignition timing, I've not met a bike motor with a knock sensor yet, I suspect it's not been considered necessary just yet as bike motors don't have the same load levels as cars. The cam sensor gives info on which stroke any given cylinder is on. Both are important, neither solely governs ignition or fuelling

Something for the mechanics to have a quick look at anyway.. Im just trying to cover a few things before it goes into the garage...

cheers!

Originally Posted by Speedy

When piston is at T.D.C. the sensor triggers the E.C.U. to tell the Ign.Coil to discharge,Causing a spark.

T.D.C. Is a little late, it should be a few degrees before T.D.C. at tick over and even earlier the higher the revs get depending on engine load.

Could the injector nozzles need cleaning? Does the bike have one injector per cylinder or two? If it has two then the closest one to the cylinder will be used at low revs and the one further away at high revs.

These sort of problems can be caused by the HT circuit breaking down. How old are your plug leads, they might need changing. You could have a coil begining to fail.

Hope this helps.
Tim

The bikes 3 years old, it has 4 injectors, 1 per cylinder. When I figure out how to get the critters off, I will see if I can give them a clean up as well, the bikes had plenty of redex running through it over the past few weeks!


If the sensor is giving an incorrect signal (well not sensor, wires are the things in question here... ) could that cause teh ECU to think its in adifferent postition than it actualy is, and cause it to fire at the wrong point ?

as said previously, when it does this thing, it feels like the engines stopped for a split second, and due to that ther is a massive amount of engine braking.. and the front will dip down on the bike violently at times...


thanks for the ideas, will do a few more things over the weekend