Right then I got a brain teaser for you

[Scottv8]

Ive had this problem for a couple of months now, spent many, many, many hours / days / weeks on it and I'm buggered if I can figure it out (I'm a qualified 'old school' mechanic so pretty good with stuff, not so great on modern computer stuff though).

Its a 2008 Stelvio 4v, 41k miles, Full service History.
Basically, its only firing properly on one cylinder (it is firing, just not fully).
Fitted new injectors (spraying well) no change
New Spark plugs (Sparking well) no change
New HT leads, no change
New ECU, no change
Swapped coils over side to side to see if the problem moves, no change.
Took apart and cleaned every electrical plug, fuse and relay ,no change.

After all that as far as I can tell, I have narrowed it down to the new injectors.
One is working fine on either cylinder,
The other one sprays but the cylinder it is fitted to does not fire fully (exhaust gets luke warm so theres some sort of fire in there).
If I unplug it that injector, it makes no difference to the running, if I leave it plugged in and unplug the 'good' one, the engine cuts out.
Checked the plugs, one is clean white ceramic (bad side), the other is a healthy brown / slight carbon (good side).

Now here's the kicker..........if I change the injectors over, the problem changes sides as does the plug colours!!!!
"So that's the injector" I hear you say.......ok, so i've now tried 7 different injectors, all with the same results!!!
1 of them is the original ones to the bike, 2 were second hand (running fine on a mates bike), 3 were cheap Chinese ones off the bay (the 4th one of the 2 sets is the 'good' one.......go figure.
And today I have received a UK pattern part for £50, exactly the same.
I really don't want to spend the £168 for genuine Marrelli one if I'm gonna get the same results.
If I could guarantee that would fix the problem, I would buy it in a heart beat.
But how can 7 different injectors be bad, cheap ones of not?

Any help or advice will be absolutely greatly appreciated,
If someone can sort it out, I will genuinely give them some sort of a reward, I really will.....
This is killing me, please help. I am trying to sell the bike and I don't really want to scrap it as i've spent A LOT of money and time on it over the years, but that's just about my next option.

 

[john zibell]

I've never needed to put new injectors into a bike. I've found having the old injectors cleaned and serviced works well. I recommend having your original injectors cleaned and serviced. In the US there is an excellent shop that does this, but for where you are check with some diesel shops to see where they have injector ultrasonically cleaned and tested.

 

[Scottv8]

I've never needed to put new injectors into a bike. I've found having the old injectors cleaned and serviced works well. I recommend having your original injectors cleaned and serviced. In the US there is an excellent shop that does this, but for where you are check with some diesel shops to see where they have injector ultrasonically cleaned and tested.

Hello John, thank you for the reply.
There are few issues with that, firstly one of my original ones had the electric plug broken, hence why I changed them in the first place, thinking that was the problem.
Secondly, places that do that are very few and far between and are not far off the cost of a new one.
Thirdly, the 'bad' one I have now is spraying just as good as the 'good' one.
Again, if I could guarantee that would fix the problem then I would have that done in a heart beat, but I'm loathed to spend anymore money throwing ideas at it to see if they stick.
Having said that, its about the only idea I have left apart from buying a new one, so may well have to give it a try.

 

[Brian UK]

Have you tried putting a generous amount of injector cleaner in the fuel? Local guy fills the fuel filter (on cars) with the stuff and runs it almost neat. But it does clean them.
The other thing to get checked is the electrical feed to the injectors. You need a specialist with an osilloscope really to compare the signals to each injector.

So out of all the injectors you currently have, only one seems to work properly and that's the good original?

 

[Scottv8]

Hello Brian,
thank you for your input and suggestions.
I have cleaned each injector with cleaner whilst powering them to open them.
I have also currently got Redex injector cleaner in the fuel tank.
I cant see theres a problem with the elctric feed as swopping the injectors from side to side moves the problem (good one runs on either side, bad one does not run fully on either side) or am i missing something there?
The only injector I have that works properly is one of the cheap chinese ones I bought off Ebay, I have one of the original Marrelli which seems to work a little as the exhuast gets luke warm and I get a popping from the exhaust when the injector is connected (stops when I disconnect it), which suggests to me that its not delivering enough fuel.
The second original had a broken plug, which I thought was the root of all my problems, hence why I bought a new set.