Injector figures

[rich21]

I had a injector knock on idle, Finally had a breakthrough i think, was on xentry and decided to run a smooth engine running after someone else on another forum said that's how he determines knackered injectors, one pic is on idle and one at around 2500 rpm, notice cylinder 4 is 67.00 us, apparently +68 is max. Would you agree its injector 4 causing the knock on idle? Also does anyone know what's the max minus figure u can have? As some of the other injectors have high minus figures, trying to decide if i need to replace all injectors, Also what do these figures mean, eg injector leakoff, injector dribbling?

 

[DREAMER NO2]

Dont think the knock you talk about is the injectors .

 

[rich21]

What do u think then?

 

[mersum1es]

Do a leak test, number 4 shows bad on idle. It means it has to increase opening time (usually due to leak) to keep running smooth, Of course you can try calibration like xentry suggest. Negative values are compensating that one which needs more fueling. I would change only #4 at first, then check what other injectors showing.

Why injector can't cause knocking? Its not rare that injector in not closing properly, peeing on cylinder (giving often knocking sound), and high risk to burn hole on piston if not repaired.

 

[rich21]

I've had intermittent problems for a while, was knocking on idle a while back and after a dose of injector cleaner, cleared the issue for a while, if I rev the car to 2600rpm all injector figures go to zero. This issue is coupled with the p2373 that nobody knows how to fix, did a leak off test a while back but it wast knocking at the time but 4 was slightly higher, I was thinking just buy a new injector from pf jones and just putting it in

 

[rich21]

How does it work when the other injectors compensate for 4, should 1 also compensate?

 

[alexanderfoti]

If you suspect knock, disable injector 4 on Xentry diag and see if knock dissappears

 

[rich21]

I've already done that but with me switching injector 4 off it idles even worse making it hard to distinguish

 

[alexanderfoti]

But does the knock dissappear?

 

[rich21]

Will try it again tomorrow and disable it when it's in drive stood still as the knocks louder. Another thing that occurs from cold is when starting it, it will churn over a and won't rev for around 5 seconds, when hot it's ok

 

[supernoodle]

Convention would normally be for energising times you add the map value and the corrections to get the final corrected value. So a + correction means it is having to increase energising time, ie cylinder is under performing. I say cylinder as these correction functions use engine speed to determine injector performance but of course there could be some other factors that influence it.

If that injector is under delivering, the knock you describe could well be the pilot injection being too small to help smooth the cylinder pressure rise rate from the main injection

I see on the screen it says if at the limit check the ZFC, which is what the fault description you gave relates to. Can you see the number of learns for each pressure and cylinder?

To prove the fault code is related to ZFC learns I would reset the learns.

 

[rich21]

We did the learns on the 250bar and the 600bar bar and this made no difference

 

[VitoVanMan]

Will try it again tomorrow and disable it when it's in drive stood still as the knocks louder. Another thing that occurs from cold is when starting it, it will churn over a and won't rev for around 5 seconds, when hot it's ok

Have you checked " The Engine Coolant Temperature Sensor's " temperature before you start up the engine?

 

[rich21]

Yeah already checked, temp seems normal, tried switching injectors off one by one today, slight knock still there, running out of ideas, tried disconnecting temp, fuel quantity control valve, fuel pressure sensor, egr same sound, just didn't wanna shot money away, might have to book it into merc, just don't want to shot money away

 

[ajlsl600]

Do a leak test, number 4 shows bad on idle. It means it has to increase opening time (usually due to leak) to keep running smooth, Of course you can try calibration like xentry suggest. Negative values are compensating that one which needs more fueling. I would change only #4 at first, then check what other injectors showing.

Why injector can't cause knocking? Its not rare that injector in not closing properly, peeing on cylinder (giving often knocking sound), and high risk to burn hole on piston if not repaired.

Swap injector, see if issue moves.

 

[VitoVanMan]

Do you have a diesel engine specialist close by, who can check the individual injectors performance on a rig. My local guy charges £25+VAT per injector and certifies performance.
How many times have you taken the injectors out, have you escaped the black death...?

 

[rich21]

Car has been into a independent mercedes garage, injector 4 is knackered and 2 is getting to that point, has anyone bought recon injectors from pf jones?

 

[rich21]

After speaking to the mercedes he said injector 4 was knackered and 2 was compensating, replace injector 4 with a new one, coded in, run slightly worse now, does the injector learning need done at 250 and 600bar before it will run correct.?
New figure's

Cylinder 1 68us
Cylinder 2 68us
Cylinder 3 37us
Cylinder 4 -68

 

[rich21]

Had another play about this morning, located hissing sound near the fuel filter, noise changed when moving pipes, possibly t piece - will take a further look later as had to go out part number I believe A6460700732

 

[rich21]

The p2373 fault has cleared after I cleared the codes and not came back, I did move every connector this morning, think the hissing noise is normal on the venturi t piece, just sounds rough on idle as if it's missing, gonna do another leak of test tomorrow, already done another compression test in xentry, came back ok