Diesel Injection, some questions

dnme

Dear Colleagues,

In recent times I have been dealing with car issues and after some research, I have a few questions. If anyone can help, I'd be very grateful.

1. Common rail
What does this mean? My mechanic says its to do with the fact that each injector gets its fuel supply from a common source (fuel pump). So where does the word rail come in? (The word rail to me means a track or guide for client objects). If anyone could explain the common rail system to me in very simple language, I'd be grateful.

2. ECU
Why do injectors have to be programmed into the ECU. I understand that the ECU controls fuel distribution so what info is actually programmed about each injector?

Many thanks for any replies

Captain Slow IRL

1) The "common" rail runs along the top of the head, and all injectors are fed with it, hence common! The injectors control the amount of fuel delivered to the cylinders (google it, it'll take too long to explain!) as opposed to the fuel pump metering the fuel on the older type systems.

2) Injectors can have their own identification code and the ecu has to know which injector is in which cylinder so it knows which injector has to be opened in relation to crank/cam position.

Mr.Diagnostic

Common rail as above by captain slow.
The fuel supply comes from a high pressure pump to the pipe, known as a fuel rail, and each injector is fed from this.

The reason injectors need to be coded is because when new they are set up and checked for delivery rate and each one is slightly different. This difference in delivery rate is represented by the calibration number. So as the ECU can accurately control the amount of fuel that is injected it must know by how much to vary it from a set point. By entering the calibration number the ECU calculates the adjustment to make for each injector.

dnme

Many thanks folks, I get it now. Just had the bad news from injector reconditioning service that all 4 are failing, so 150 quid each:eek: and we now have to check fuel pump for iron filings / wear. Jeez I cant afford this crap.

Captain Slow IRL

150 isn't a ridiculous price for an injector - you could have paid a lot more!
Best of luck with the car.

dnme

Captain Slow IRL wrote: »

150 isn't a ridiculous price for an injector - you could have paid a lot more!
Best of luck with the car.

Hi Captain Slow IRL and thanks

Thats €150 each for reconditioning, not for replacing. My Renault mechaninc quoted me €420 each for new ones!!!!!:eek:

While I'm here, it may transpire that I have to replace the fuel pump, I'm having the fuel filter checked tomorrow for metal particles / filings. Can anyone tell me where I might go to price a pump? I have tried google but got nowhere.

Many thanks

Mr.Diagnostic

dnme wrote: »

Hi Captain Slow IRL and thanks

Thats €150 each for reconditioning, not for replacing. My Renault mechaninc quoted me €420 each for new ones!!!!!:eek:

While I'm here, it may transpire that I have to replace the fuel pump, I'm having the fuel filter checked tomorrow for metal particles / filings. Can anyone tell me where I might go to price a pump? I have tried google but got nowhere.

Many thanks

Renault dealers in the UK supply those injectors for £355 plus vat for a set of four. The reason they supply four is the same reason you need four, they usually fail once they are removed. It seems the needles seize and very occasionally free up after a drive.

dnme

Mr.Diagnostic wrote: »

Renault dealers in the UK supply those injectors for £355 plus vat for a set of four. The reason they supply four is the same reason you need four, they usually fail once they are removed. It seems the needles seize and very occasionally free up after a drive.

Mr.Diagnostic

1. Can you clarify this please? Are you saying £355 plus vat for all four (£88.75 each)?
2. Are you saying that my injectors which have been sent to a electricial dielel engineer will fail now because I have removed them?
3. Can you provide me with a website or contact for above UK Renault dealer? (I am coming up blank on google)
4. Would these dealers also provide a fuel pump? how much would you reckon?

Many many thanks - you may just be about to save my life (I really mean that)

Mr.Diagnostic

1. Yes, that’s correct, sterling of course.
2. No, if rebuilt they should be ok. Just no point in rebuilding them due to cost.
3. All the UK dealers should be the same price. I don’t have the dealer details now but can get them on Monday. Should be easy to find on google anyway.
4. Not sure on the pump. You could check the price at the same time.

dnme

Can I ask, how do you know th eprice so precisely? have you purchased a set of injectors recently? where did you get the price from?

Also, if I ring a UK dealer, will he not then tell me that I have to purchase via an Irish dealer?

many thanks

Mr.Diagnostic

Its part of my business to know. Also, I looked it up before I posted

The dealer will be happy to sell to you.

dnme

Mr.Diagnostic wrote: »

Its part of my business to know. Also, I looked it up before I posted

The dealer will be happy to sell to you.

I think thats what I'm trying to get at. Would you mind me asking where did you look it up ?

In all my efforts at finding UK Renault dealers, their contact forms all require UK postcodes with the dreaded "find address" button.

Again, I hope I am not offending you here and sincere apologies if I am over steping the line. I just cant find what you seem to be eluding to at all so I need a pointer in the right direction. If you are unhappy publishing details, then perhaps you could pm me ?

Again many thanks

Mr.Diagnostic

I don’t mind you asking at all, its not something you can access though.

A tech support customer of mine purchased these injectors a couple of weeks ago. He included the price is his closing email. Based on where he is located I would imagine he dealt here http://www.dealer.renault.co.uk/lookers-macclesfield/GeneralContact.aspx (the phone number is in the top right). The price matches what I have heard before and I know other customers from outside the UK have purchased from UK dealers. If you have any problem with the dealer PM me and I will check the source.

dnme

I'm sincerely grateful to you, I will get on to this on Monday morning.

dnme

It transpires, after further inspection, there are particles in the diesel which indicates that the high pressure fuel pump is disintigrating (a common issue with them).

So, my requirement has now escalated to the following


(a) 4 x Diesel Fuel lnjectors

(b) Injector pipes (injector to fuel rail pipes) and possibly the fuel rail itself?

(c) 1 x High Pressure Fuel Pump

(d) Timing belt kit (not including water pump)

(e) Alternator belt

paddyp

dnme wrote: »

It transpires, after further inspection, there are particles in the diesel which indicates that the high pressure fuel pump is disintigrating (a common issue with them).

So, my requirement has now escalated to the following


(a) 4 x Diesel Fuel lnjectors

(b) Injector pipes (injector to fuel rail pipes) and possibly the fuel rail itself?

(c) 1 x High Pressure Fuel Pump

(d) Timing belt kit (not including water pump)

(e) Alternator belt

This is fairly standard with common rail failure I'm afraid. A lot of manufacturers even change the fuel tank, lift pump, filter housing, fuel pipes. At a main dealer out of guarantee you're looking at 3k-6k euro.

Diesel pumps and injectors rely on the fuel for lubrication, any water or emulsifying substance present and instant damage. The pressure in modern common rail systems is 1500-1800bar (21700psi to 27000psi) imagine the consequence when lubrication is compromised. You NEED to check the tank.

Also a warning to people a LOT of diesel additives are not suitable for common rail engines they contain alcohol which carries the water though the filter and can wreck your engine. There are a couple of products such as wynns injector protector which specifically improve lubricity and contain a demulsifying agent to demulsify water and stop it at the filter.

The clearances in the injectors are of the order or 2 micron and it only takes a tiny bit more clearance to render then useless. Water pushed through the injectors at the pressures mentioned cuts channels in the injector needle and needle bore.

Forget rebuilt injectors. The local bosch service center told me they have about a 10% success rate beyond the short term with reconditioned injectors. Which if you can comprehend the tolerances above you'll understand why.

Personally I have gotten away with reusing the rail to injector and rail to pump pipes. Also you can have the rail cleaned the ends come out.

Next time I'm doing the job I'll be buying a second hand engine (that I have seen and tested running) for about 500 euro. Factor in about a days labour and you still come out on top.

dnme

Hi paddyp

paddyp wrote: »

Diesel pumps and injectors rely on the fuel for lubrication, any water or emulsifying substance present and instant damage. The pressure in modern common rail systems is 1500-1800bar (21700psi to 27000psi) imagine the consequence when lubrication is compromised. You NEED to check the tank.

Check the tank for what? water? if so, isn't it just a case of bleeding thre tank?

paddyp wrote: »

Forget rebuilt injectors. The local bosch service center told me they have about a 10% success rate beyond the short term with reconditioned injectors. Which if you can comprehend the tolerances above you'll understand why.

so, Im doing the right thing by purchasing new injectors, recons are useless ?

paddyp wrote: »

Next time I'm doing the job I'll be buying a second hand engine (that I have seen and tested running) for about 500 euro. Factor in about a days labour and you still come out on top.

what are you buying a second hand engine for?

Mr.Diagnostic

I am guessing at this stage you have figured out how complicated this subject is

The point that paddyp makes about rebuilt injectors is, in my experience, caused mainly because most specialists who rebuild them are not properly equipped to do so. The equipment cost involved is almost beyond belief.
I cannot stress enough how important it is to keep the system clear of contaminants. This is the reason that misfueling with petrol does so much damage.

The reason the tank needs to be cleaned or replaced is because the metal particles from the pump will be in there as well. Also it needs to be spotless as regards contaminants like water etc which could have caused the problem in the first place.
The theory behind replacing the whole fuel system, inc the tank, is that the minute metal particles etc may not be washed out completely. In my experience, I have seen new injectors fail in a short time when the system was not cleaned out but never when it has been so I am not convinced of the need to replace everything. Flushing is vital though.
To give you an idea of what the manufacturers recommend. Denso insist that all their service agents have a clean room, similar to what you would find in microprocessor manufacturing.

I think the point paddyp made about buying a tested used engine was that it would come with working pump and injectors. I am not sure I would agree with that (sorry paddy) because you could be buying a problem that is just about to happen. Probably not a good idea if you plan on keeping the car long term.

dnme

Mr.Diagnostic

Many thanks for the great info. Why would metal particles originating from the high pressure pump travel backwards though ? (ending up in the tank) ? Surely all contaminants from fuel pump will travel forwards - many will get caught by filter, the rest get through to injectors and damage starts.....no?