Couple of questions about diseasels

[E-bmw]

I am having a couple of issues getting answers to a couple of questions surround a slight problem I may have.

1. Typical diesel fuel pressure at injector on common rail diesel engine, specifically a 1.6 D2 Volvo/PSA/Ford engine?

I ask as the engine seems a little lumpy around 1200 - 1800 rpm & would like to see the injector spray pattern and do have enough stuff to possibly do this myself & then just send any poor ones in for refurb rather than do them all if none need doing.

2. I have a very small amount of injector blow by that I can't seem to stop, is it going to be an issue aside of me having to clean/redo them every 6 months or so?

I have replaced washers/recut the seats/replaced & re-torqued (specifically 4nm + 65 degrees) the bolts a few times on all & still have 2 that just refuse to actually stop blowing by slightly. Not enough to detect exhaust gases in the engine bay, but they both get a bit carboned up after a few months.

Edited by E-bmw on Monday 7th October 15:49

[stevieturbo]

Typical CR is several thousand psi.. This is not something that can be DIY tested.

And even some places who do it as a business....even their tests are not always conclusive.

Is fuel pressure not meeting target on the scantool ? What sort of pressure is it seeing ?

I know some cars the ecu can give some feedback on injector performance and how flow is, not sure if yours might do this ? A proper scan tool should offer the info.

[E-bmw]

stevieturbo said:

Typical CR is several thousand psi.. This is not something that can be DIY tested.

And even some places who do it as a business....even their tests are not always conclusive.

Is fuel pressure not meeting target on the scantool ? What sort of pressure is it seeing ?

I know some cars the ecu can give some feedback on injector performance and how flow is, not sure if yours might do this ? A proper scan tool should offer the info.

I do actually have a test pump that can deliver up to 700 bar/10k psi that I was going to try with.

I must admit, I didn't think to look at the live data to see what it is reporting, will have a look tomorrow.

Injector flows all look similar around 0.97/1.03 (can't 100% remember the units) could it be micro g/rev?????

[E-bmw]

Any thoughts on the second question ST?

[Arlen]

When you re-cut the seats did you change the washers to thicker ones?

I know that there are varying thickness injector washers available and when having re-cut seats I have fitted thicker washers to account for the material removed in the process.

This could explain the blow by.

[E-bmw]

Arlen said:

When you re-cut the seats did you change the washers to thicker ones?

I know that there are varying thickness injector washers available and when having re-cut seats I have fitted thicker washers to account for the material removed in the process.

This could explain the blow by.

I have to admit, I did not as the amount removed seemed very small.

Could this be significant?

ETA.
The standard size is 2.0mm.

A quick look round says I can also get them in 2.5 & 3mm thicknesses.

Edited by E-bmw on Tuesday 8th October 10:26

[Arlen]

E-bmw said:

I have to admit, I did not as the amount removed seemed very small.

Could this be significant?

ETA.
The standard size is 2.0mm.

A quick look round says I can also get them in 2.5 & 3mm thicknesses.

Edited by E-bmw on Tuesday 8th October 10:26

I would say likely, as the injector seats at the top of the cylinder onto a solid base, that can only compress the sealing washer to a certain point. Therefore with material removed the injector cannot compress into the sealing washer which allows blow by.

Cheap enough to try and replace them.

[E-bmw]

Arlen said:

E-bmw said:

I have to admit, I did not as the amount removed seemed very small.

Could this be significant?

ETA.
The standard size is 2.0mm.

A quick look round says I can also get them in 2.5 & 3mm thicknesses.

Edited by E-bmw on Tuesday 8th October 10:26

I would say likely, as the injector seats at the top of the cylinder onto a solid base, that can only compress the sealing washer to a certain point. Therefore with material removed the injector cannot compress into the sealing washer which allows blow by.

Cheap enough to try and replace them.

Fair comment, I will pick some 2.5s up.

[stevieturbo]

E-bmw said:

I do actually have a test pump that can deliver up to 700 bar/10k psi that I was going to try with.

I must admit, I didn't think to look at the live data to see what it is reporting, will have a look tomorrow.

Injector flows all look similar around 0.97/1.03 (can't 100% remember the units) could it be micro g/rev?????

Creating pressure is one thing, controlling the injector as it opens/closes is another. Depending on type, it can be a hundred or so volts to open, and for very very short pulse widths, and some injectors then require reverse polarity to close them.
I can see no part of modern injector testing being DIY.

When you say blowby, as in combustion past the seals ? or leakback/diesel down the return lines ?

As others suggest, it's typical to need to recut seats when changing the copper washers. Which I guess could lead to oversize washers being needed ? if that's a thing.
I've only done a few ( current car actually needs it done, I just can't be arsed though lol ) and the injector mounting and clamping method seemed fairly flexble, doubt you could ever cut a seat so deep they wouldn't clamp and seal again.

[FMOB]

Can you not read the fuel rail pressure using a dongle and vehicle diagnostics?

The fuel rail will have a pressure sensor that the ECU can read.

A quick google indicates the pressure used by common rail diesels is huge i.e. up to 29000psi.

[E-bmw]

stevieturbo said:

E-bmw said:

I do actually have a test pump that can deliver up to 700 bar/10k psi that I was going to try with.

I must admit, I didn't think to look at the live data to see what it is reporting, will have a look tomorrow.

Injector flows all look similar around 0.97/1.03 (can't 100% remember the units) could it be micro g/rev?????

Creating pressure is one thing, controlling the injector as it opens/closes is another. Depending on type, it can be a hundred or so volts to open, and for very very short pulse widths, and some injectors then require reverse polarity to close them.
I can see no part of modern injector testing being DIY.

Fair comment, I was not aware of that, just assumed they would be 12v open 0v close, never mind.

stevieturbo said:

When you say blowby, as in combustion past the seals ? or leakback/diesel down the return lines ?

Combustion gases past the copper washer, only slight, but definitely visible when you squirt a bit of water/detergent mix on them as a tell-tale.

stevieturbo said:

As others suggest, it's typical to need to recut seats when changing the copper washers. Which I guess could lead to oversize washers being needed ? if that's a thing.

Yes, I have recut them, once again, not by a lot & was operating on the assumption that the one single bolt on its rocker would take up the difference, but then I suppose it would be at a very slightly different angle, which could be the issue.

I've only done a few ( current car actually needs it done, I just can't be arsed though lol ) and the injector mounting and clamping method seemed fairly flexble, doubt you could ever cut a seat so deep they wouldn't clamp and seal again.

My thoughts exactly as above, hence why I didn't change the washer thickness.

I will give the 2.5mm washers ago (+0.5mm) and see if that helps.

[E-bmw]

FMOB said:

Can you not read the fuel rail pressure using a dongle and vehicle diagnostics?

The fuel rail will have a pressure sensor that the ECU can read.

A quick google indicates the pressure used by common rail diesels is huge i.e. up to 29000psi.

Yes, I can (didn't get the chance today, and won't for the next few days but as per my reply to ST, I am now more aware of the pitfalls & so will just have to pass on the test.