Injectors misbehaving but trying to understand the numbers

[MattBLancs]

Great lesson there. Thanks Matt. Good to know.

Happy to share what (little) I know! And glad of this great place where do many all do the same! "Collective intelligence"
https://en.wikipedia.org/wiki/Collective_intelligence

[darbuck]

Thanks Matt, No but it shouldn't be a million miles away either
Edit
Totally agree it's a great forum

[Rhothgar]

What’s up with your C5 then, Matt?

[darbuck]

Yes sorry Matt what's up with the c5

[MattBLancs]

It's heard I was planning to find a replacement for it (which I since have, the Blue 308 SW) so it's promptly refused to run. I think it's fuel delivery, air into the fuel lines issues.

I've changed a few fuel pipe connector O-rings and bought an in tank fuel pump (which it does without as standard) as backup plan.

But in fairness I haven't had much time to tackle it, so it's just annoying me slowly ticking down it's MOT whilst it sits there. Must get it sorted....

viewtopic.php?p=805172#p805172 = when it played up again.

[darbuck]

It sounds like the high pressure pump is on the way out. Is she turning over quickly enough, I had similar with a mk 1 turned out to be a weak starter didn't sound bad but was.

[Rhothgar]

Weird. I cannot find a video. The link takes me to page 82

[darbuck]

Hi lads I checked the regulator it's definitely 38% at idle and doesn't seem to go above 40% when I rev it. The 1 and the two injectors that go to -147us correction are showing control in that they bounce around a bit before going to this number. Injector 4 bounces around the -50s and 60s so it is controlled if taking fuel away but without knowing what the numbers really mean I can't confirm it.The injector 3 though goes straight to 143.14. I think the ECU thinks that it's controlling correctly.

[Rhothgar]

If you graphed it you would see a pulse width modulation wave ie on, off, on, off but such that it is "ON" 38% of the time. The fuel pressure sensor tells the ECU what pressure there is in the rail and the mapping will tell the fuel pressure regulator to open for slightly longer when the load increases ie acceleration so it would depend on how hard you revved it as to whether it called for an increase in the open cycle ratio.

Now here's a thought!

Diagnostics on an RHZ and this will no doubt be the same.

With the engine warm, at idle, the flow correction should be between -3 and 3 mg/stroke inclusive. If you disconnect the fuel return pipe on each diesel injector in turn the flow should be a slow drip, if the flow is continuous the diesel injector is seized. The manual doesn't say whether that means it is seized shut or seized open and that would be useful to know because if it meant it was seized shut then you would expect the opposite if it was seized open and peeing fuel in. I won't give you the wiring test specs as I do not have a wiring diagram for your car.

[darbuck]

I think it is supposed to be slightly higher on 5 or 6 but I cant find a menu that shows this. I revced her to 2500-3000 rpm so I would have expected something in the region of 50 or 60%. Leave it with me I will do another leak off test and come back to you. It will tonight at the earliest

[MattBLancs]

It sounds like the high pressure pump is on the way out. Is she turning over quickly enough, I had similar with a mk 1 turned out to be a weak starter didn't sound bad but was.

Yes could be that pump is giving in. Hoping the tiny bubbles you can see (not many, tiny and it's always done that when running over several years of my ownership) are the vacuum leak and so are easily fixed.

Turns over lovely and quickly, nice big chunky new starter motor fitted during the first instance of the issue.

Battery healthy and I've tried turning over whilst battery boosted by a second car (running) coupled up with jump leads (no difference)

Weird. I cannot find a video. The link takes me to page 82

Sorry that's me - link is to page 82 of my blog and is it going wrong recently, there's a link on that post to the (multiple pages!!) long drawn out fix first time around.

I may take a tentative first step into YouTube and create a video (at the weekend)

I'll not divert this thread with my C5 issues as it'll get confusing!

Fuel rail:
Just bare in mind the fuel demand for a diesel engine to run all the way to redline, without load, is tiny (as it's only having to overcome the engine's own internal resistance) compared to when it's pulling the car along / accelerating. Guess not much change in what logged at fuel rail in unloaded condition.

[darbuck]

Ok so fuel pipes need new seals, starter ruled out so most likely the pump so unfortunately. If you get her running and you get a chance to record injection values can you get the regulation data as well just as a reference I know they are different engines but I would like to see if it moves around a bit.

[Rhothgar]

Fuel rail:
Just bare in mind the fuel demand for a diesel engine to run all the way to redline, without load, is tiny (as it's only having to overcome the engine's own internal resistance) compared to when it's pulling the car along / accelerating. Guess not much change in what logged at fuel rail in unloaded condition.

Exactly. They are VERY efficient when not loaded. In fact, aren't pumps rated in bands of bhp? Sure I read something like that about the Bosch VP20 pump

[darbuck]

All pumps are power rated IE kWh/bhp depending on your preferred language mine is a bit of a mishmash. Schools changed to metric here halfway through my schooling so a bit a mess.

[MattBLancs]

Same here, I can visualise best in millimeters, inches, metres and miles,

Power best in bhp unless electric motors then tending towards kW,

Weight in grams, kilos, tonnes, (not good with Stones)

Volumes in CC, pints, litres, gallons, sometimes m³

Speed m/s and mph