I have just driven a friends 607 because he was complaining of a engine knock starting at about 3000 rpm, before that speed all is quiet. I would gess that its a fuel injection problem but not being familier with common rail engines I cant be sure. I have heard most noises from years of IDI engines but this doesn't sound like anything I have heard before. It sounds like a mechanical noise at half engine speed, so I assume it is only affecting one cylinder, but it is only there when the throttle is open wide, when you back off it all goes quiet again. Can anyone help? Thanks
Peter.N.
Edited by Pugugly {P} on 14/12/2007 at 21:16
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Peter
Could be an internally cracked injector, a piston/end problem, or even a dual-mass flywheel or crank pulley coming apart.
Injector faults will show up on individual injector leak-off rates and in the injector correction figures for each cylinder. Do not disconnect a Piezo injector with the engine running as that will instantly drill a hole through both the piston - and the sump.
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Thanks Screwloose.
As I say I know nothing about common rail engines although I have had about 50 years experience with IDIs, so your injector information is appreciated.
I dont think it is a mechanical problem because there is no vibration whatsoever, in fact the noise isn't all that loud, if it was my car I probably wouldn't worry about it, especially as it is not present in normal driving, but then not knowing the engines I dont know what it might lead to.
Thanks again
Peter.N.
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Do not disconnect a Piezo injector with the engine running as that will instantly drill a hole through both the piston - and the sump.
:-O
Holy cow! These cr systems are terrifying!
Cheers
DP
--
04 Grand Scenic 1.9 dCi Dynamique
00 Mondeo 1.8TD LX
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Peter
There is a known issue with certain HDi injector faults that produce a loud "tappet-like" noise over 2500 revs under load.
If you've got experience of IDI units; then either use the proper bottle set or find some clear plastic tube and cut a few feet off for each injector leak-off. Bind them together and hang them uphill to the bonnet catch. Block the detached leak-off hose. The return flow from the pump is huge.
Idle the engine for a few seconds and watch them fill; a cracked injector will leak five times more than a good one. You can repeat this test with the pressure reg off; but that will set a code that won't go until cleared with a scanner.
The running pressure in the rail is 1600+ bar [25,000 lbf/sq/in.] Pipes are one-shot-use; disconnect and you replace. Near-invisible leaks can be fatal; if you suspect a leak, lay paper, shut the lid and start it. Any fuel on the paper and you have a leak. Basically; just take reasonable care, these things do bite.
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Thanks again Screwloose
That sounds like problem, a 'tappet like' noise is how I would describe it, and thanks for the warnings! This is my first excursion into the world of HDI, I well remember the warnings given in the Perkins manuals of the '50s as to the danger of these super high pressures - 2,000 psi!.
If this does prove to be the problem, I have seen several sets of injectors on ebay for a reasonable price, would they be an option, and if so does the system have to be reprogrammed, and again if so, what would be the likely cost.
Peter.N.
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Peter
I've never had any success with secondhand HDi injectors. They each have [had!] a grading letter [or number] printed on them that is entered into the ECU's configuration for that particular cylinder. [Numbered backwards on these! No.1 is flywheel end.]
It's unlikely that these are the type serial-coded to the ECU, as those would still be under warranty. Getting someone with a scanner to check codes etc. is still a very good idea.
Personally; I'd identify the faulty[?] injector and replace just that one [and feed pipe] with a new one with a similar grade identifier. Unlike IDI injectors; these don't need regular servicing/tip replacement and [@£500 each] you don't commonly change sets. [The 5 nozzle holes are only 2 microns across; but they stay clear at that pressure.]
The other advantage of only replacing one is that these seize/melt into their plastic liners and often need a special slide-hammer to extract at least one of them.
Anyway; before all that, time for proper testing to prove the point one way or the other. Common-rails are the hardest things on the road to diagnose and this is still all conjecture.
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