Rough idling and driving after injector seal change.

[JORD1DOTCOM]

I've been plugging and unplugging in various sequences and if I pull 2 and 4 they do make a slight difference but not much.. would this mean that the connection is good but the functionality is bad as it seems to acknowledge some sort of connection.. if so would you recommend cleaning them as I'm so close to taking the injectors out and apart for a thorough clean.. also I just realised the fuel is basically empty ..would this make things worse (I'm thinking no as it doesn't seem to be an air lock)

 

[m80]

My guess would be air locks.
I haven't a clue is these air lock within the injector, or in the fuel pipe.
Nothing to lose by cracking the line at the injector methinks.

Happy to be better educated by better experience though.

 

[mersum1es]

Piezo injectors air locks are common, and pretty difficult to solve. Cracking pipe open won't help. Like said SDS has purge option, but even that won't always help. That's why it is recommended to change only one injector at time, and then run engine for a while. I know running at high revs have helped often, but that is always a small risk. Back in time there was a video where guy explained where air lock is building, and how to resolve it (by disassembling injector).

 

[JORD1DOTCOM]

I have only run the engine for around 10 15 minutes on the drive as it stalls when I put it in gear.. this doesn't feel like enough time to release it from what I'm hearing.. but as I can't get off the drive would you recommend just running it at high rev... would this sort out the recently lit up CEL... also I have taken injector apart and cleaned but the same happens.... I'm thinking/hoping air lock but would that bring on the management light??

 

[m80]

It's a guess but the knock sensor/s might bring up the dash warning.

 

[Supernoodle]

Certainly do not attempt to disassemble a common rail injector unless you have experience and somewhere sterile to do it.
Nozzle hole diameters are of the order of 150 micron. Clearances internally are even smaller. Even cleaning the outside of the you have to be careful. On the HP inlet there is a little edge filter too. Even if you do get the injector back together the correction code will be void.

The airlock on a piezo injector is actually the hydraulic amplifier empty of fuel. The piezo stack expands a very small amount when energised, not enough to move the control valve directly. The surface area of the piezo is large compared to the control valve, so the volume of fluid displaced by piezo translates into a longer movement at the smaller control valve.
If that hydraulic amplifier is not full with fuel the control valve can't open. No control valve movement means no nozzle opening and no injection.

To ensure that the amplifier is kept full of fuel there is a little pressure holding valve in the fuel spill line.
Empying the amplifier isn't that easy though, you'd have to push a lot of air through the high pressure fuel side to do that. If you do that, normally they'd all be empty, not just one or two.
If you did have just one or two empty or say put on a recon part, the suggrstion of just running the engine works as the spill from the working injectors would fill up the spill line and the empty amplifier.
In a test environment the preferred way is to apply fuel under pressure to that holding valve. It will open, allow fuel in and fill the amplifiers. You shouldn't attempt this unless you know what you're doing as if you reverse pressurise the fuel pump you'll invert the seals and you'll be in a right mess.

 

[JORD1DOTCOM]

I stripped injector 4 and cleaned it which was dirty again on the tip.. there is a difference in the revs when I unplug it but doesn't stall but 1 and 3 still stall if I pull them out..also I have checked the electrical pins and they seem OK

 

[JORD1DOTCOM]

I've spoken to my colleague who happens to be a mercedes approved mechanic... he told me my engine is the 651 and he's had to do chain work on these over the years... in doing so he said he had gone through a fair few injectors because as soon as you lay these Delphi injectors down they can lock in open or closed (KEEP THEM UPRIGHT) also if they dry up... all things are pointing to this... I have spoken to an injector refurb place near me, they knew straight away and told me I had delphi and they are prone to this so...£15 each to test and £65 each to sort the airlock or if they need repairing in any way its £85 each... lesson's have been learnt... definitely should have researched more on specific injectors... hopefully this will solve the issue as they were working fine before I left them on their side in my boot for a week.. I'll post an update towards the weekend. And thanks for everyone's help and advice..

 

[m80]

I've spoken to my colleague who happens to be a mercedes approved mechanic... he told me my engine is the 651 and he's had to do chain work on these over the years... in doing so he said he had gone through a fair few injectors because as soon as you lay these Delphi injectors down they can lock in open or closed (KEEP THEM UPRIGHT) also if they dry up... all things are pointing to this... I have spoken to an injector refurb place near me, they knew straight away and told me I had delphi and they are prone to this so...£15 each to test and £65 each to sort the airlock or if they need repairing in any way its £85 each... lesson's have been learnt... definitely should have researched more on specific injectors... hopefully this will solve the issue as they were working fine before I left them on their side in my boot for a week.. I'll post an update towards the weekend. And thanks for everyone's help and advice..

How does this work if they are delivered.
I'm not sure "This way up" will always be respected in transit.

 

[JORD1DOTCOM]

How does this work if they are delivered.
I'm not sure "This way up" will always be respected in transit.

Apparently they have a wax insert after build/rebuild which holds pressure where needed amd melts away after installation