TD4 tapping

Hi all i have a 2001 freelander td4 with 107k on the clock i bought it with a suspected injector knock i have spent a lot of money having a new injector and full service done but it still knocks and wont rev past 2.5k revs the engine runs smooth and pulls well does anyone know what it could be? thanks martin

wont rev past 2.5k

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good chance it be the low pressure fuel system
i.e. the electric fuel pump / fuel filter
that pump usually starts to be past its use by date at about 70k miles
its not repairable .. only option is to replace it ..
best to replace it with the original bosch type .. cheaper ones often wear out sooner ..

do a forum search for the low pressure fuel system on the 2001 year td4s
as they differ to later models
( i think most bits reside in the engine bay .. whereas later models have it under the rear wheel arch )

when the low pressure system won't deliver the required pressure on demand
the ecu limits the revs to protect the high pressure fuel system ..

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another thing to check would be the fuel rail pressure sensor
the plug/socket must be clean .. free of corrosion ..
water ingress there is a common issue ..
working voltage is small .. from millivolts to 5 volts

using 'contralube 770' on the clean plug/socket pins will defeat corrosion forming
( http://www.autoelectricsupplies.co.uk/product/827/category/154 )
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just noted ..

and full service done

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did they give you a list of what they did ?

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but it still knocks

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not 100% sure if the above would cause diesel knock
'knock' is usually a bad injector spray pattern
faulty / dirty nozzle .. leaking .. etc
or the fuel itself ..

not a bad idea to use a good diesel additive ..
to keep injectors clean and lubricated ..
'diesel rhino' available online only ( google it ) .. or
'millers eco-max' from halfords are good ones ..

i used to get a bit of 'knock' ( slight pinging ) on mine at lower rpm / before the turbo would kick in properly
that vanished after using 'diesel rhino' for a while

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here's a page of td4 faults ..
some things are different as it's written about a rover ..
e.g. the turbo is different ..

td4 engine faults :
http://tuning-diesels.com/75Zt/R75faults.htm

about the 'maf' sensor :
http://tuning-diesels.com/75Zt/R75maf.htm

hi there

thanks very much for your reply, the service was genuine LR air filer, oil filter, fuel filter and pollen filter supplied by me and the BMW cyclone crankcase breather also supplied by me with Castrol Oil (correct grade) again all supplied by me.

I have been using it today and it seems to have loosened up a bit, it drives very smooth, idles very nice and it will rev freely now, but it wont rev past 2.5k rpm while in park....

the knocking is still there is just a continuous knock knock knock on tick over and gathers speed with increased RPM and disappears above approx 3k rpm i spoke to the garage again and they said after they put it all back together after replacing the injector they was surprised it still knocks they said if you touch the injector you can feel something hitting the bottom of the injector in time with the knocking. they said it could potentially be a small end that's gone and the piston is now hitting the injector (I'm not sure if this would be a correct diagnosis) as surely it would knock throughout the entire rev range

thanks again for all your help ill have a good read up on the links you have supplied

thanks again

martin

maybe one of these would be useful

"edit" it won't let me post the link .. grrrrrrrr
anyhows .. google 'mechanics stethoscope'
amazon/uk has them ..

am tempted to get one myself ..

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but it wont rev past 2.5k rpm while in park....

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it's an automatic tranny ?
if so maybe that issue has to do with the gearbox
i.e. maybe ( as in i-don't-know ) it purposely limits the rpm in 'park'
post a query in a new thread ?

think i read somewhere that the manual gearbox ones are rev. limited when in 'neutral'
don't know if that's true or not .. i've only raised mine to 2k in 'neutral' .. gently like ..
was taught never to rev. diesels 'off-load' .. maybe that doesn't apply to modern car diesels

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i think most modern c.r. diesels employ multiple injections per cycle to defeat the 'diesel knock' that's associated with older type engines ..
i know the td4 has at least 2 injections per cycle
( so in theory if the second injection failed to materialise .. then pronounced 'diesel knock' would occur )

anyhow .. slightly confused now if your on about a mechanical knock / tap
or diesel combustion 'knock' or 'clatter' ..

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mine has had a slight tapping sound .. more evident at idle .. can't distinguish from other engine noises at higher rpm
these days i hardly ever hear it .. ( or 'notice it .. maybe it's more evident in hot weather ..
or has quietened down since i changed oil type ( now use 0/40 synthetic .. 'n some 'zx1' now and again )
early on i figured it sounded more like camshaft rpm ..
anyhow .. trying to home in on the sound .. i figured it were the vacuum pump
( top rear of engine passenger side .. driven by camshaft )

piston hitting the injector don't sound to good .. hopefully that ain't the case !
i suppose putting a finger on the injectors in turn with engine running will tell you

had a big end bearing go on me once .. old type hgv 'cat' engine ..
sounded like a low rumbling .. only sussed it cause i knew that engines sound very well after a couple of 100k miles driving it ..

btw: a mechanic 'tap' of 1 per crankshaft rotation ..
at 3k rpm that would be 50 per second ..
frequency could be high enough to make it hard to distinguish from other sounds
( that's just a theory )
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that t4 faults page does list some points that might limit the rpm ..

mine started hitting a brick wall at 3k rpm even in 3rd gear .. ( at 76k miles )
as the lp.pump was noisy and the fuel filter change date way past due
had both changed .. .. solved that issue ..

As anyone taken time to check that one of the old copper seat ring on the injectors as not been left in place once the injectors as been replaced ? just a thought, also try using the best diesel you can premium is best as opposed to supermarket diesel in my opinion,