Testing injectors whilst on vehicle.

Oil Leak · Dec 13, 2010

Hello.
I've got a '95 disco 300tdi with a smoking problem. Will smoke around 2000rpm with engine hot or cold, slight hessitation too. Otherwise the truck is running good.

Is there a simple way to test the injectors while still on the vehicle?
I read somewhere that if you loosen the fuel supply to one injector at a time, then rev to see if it still smokes, if no smoke then i've found the culprit??

Anyone know if i'm barking up the right tree here??

thanks

nrgserv · Dec 13, 2010

reasonable way to find a faulty injector, normally associated to rough running.
what colour is your smoke?
2000rpm is around the waste gate closing on the turbo, if its blue smoke you may have an oil issue.

Oil Leak · Dec 13, 2010

Yes the smoke is sometimes blue. what do you think the problem could be then?
this has been an ongoing problem since I bought the disco. I've done a whole list of stuff to her but nothing remedies the smoke

.

is a sticking wastegate unstickable??

thanks for reply.

Oil Leak · Dec 13, 2010

interesting.... i had a search for tdi wastegate probs and came across a useful trailerfitter vid on youtube.
I just had a poke under the bonnet, but dark now so had to give up..
It looked like the fatter rubber pipe from turbo to wastegate was splitting. I didn't want to push it too hard as it looked like it would come off/break.

I couldn't see if it was actually split right through/holed. If it was, would it cause smoking.

Due to location of the wastegate actuator I was unable to push/pull the rod at all.

The short rubber hose in question definately needs replacing. Anyone know where to get one from???

thanks all

jamesmartin · Dec 13, 2010

waste gate works by by the tube passing pressure to waste gate diaphragm as pressure increases diaphragm pushes on rod and starts to open waste gate reducing boost pressure from turbo hence the need to stop waste gate opening for increased performance ,tdis are very good when it comes to piston /bore sealing so would look to turbo passing more oil than usual for cause of blue smoke

nrgserv · Dec 14, 2010

Oil Leak said:
interesting.... i had a search for tdi wastegate probs and came across a useful trailerfitter vid on youtube.
I just had a poke under the bonnet, but dark now so had to give up..
It looked like the fatter rubber pipe from turbo to wastegate was splitting. I didn't want to push it too hard as it looked like it would come off/break.

I couldn't see if it was actually split right through/holed. If it was, would it cause smoking.

Due to location of the wastegate actuator I was unable to push/pull the rod at all.

The short rubber hose in question definately needs replacing. Anyone know where to get one from???

thanks all

the waste gate is incorporated with the turbo.
you probably wont be able to push it anyway.
a holed turbo pipe wont usually cause smoking.
a collapsing pipe on the suction side of turbo will cause air starvation, giving an impression of over fuelling. black smoke results.
a collapsing pipe on suction side side will cause increased vacuum, causing it to suck from where ever it can. if theres an oil breather pipe here, it could suck more than oil vapour, causing blue smoke.
as above, but could suck oil from turbo bearings.
if turbo bearing worn, will suck oil anyway.

disconnect intercooler to manifold pipe and see if your smoke disapears. perfomance will be crap with this off.
check internals of intercooler and assosiated pipework for oil.

Oil Leak · Dec 14, 2010

thanks for replies.
Recently flushed intercooler, no excessive oil/muck in it, no oil in intercooler hoses, hoses not delaminating but they are a bit soft - maybe need renewing.
I did once try flooring it when it smoked/hessitated - I got a huge trail of white smoke behind, completely filled the road.

also of note - oil consumption is minimal, coolant too

thanks again

nrgserv · Dec 14, 2010

white smoke is a sign of water in the cylinders, but not to the extent of filling the road. this sounds like unburnt diesel at the moment.
is the hesitation always there at 2000rpm, does it go away after time, or is it intermittent?
how long have you had the disco?

landymanmel90 · Dec 14, 2010

Got a mate with same problem only smokes at 2000 revs and struggles.
Thick blue smoke that seems to stick to anything it touches road,trees,fence,ppl lol.
Diconected turbo pip n run again still the same but ok in any other rev range.
Checked injectors seem ok.
thinking valve,valve seal,cracked piston,or oil rings....hmmmm

Oil Leak · Dec 15, 2010

nrgserv said:
white smoke is a sign of water in the cylinders, but not to the extent of filling the road. this sounds like unburnt diesel at the moment.
is the hesitation always there at 2000rpm, does it go away after time, or is it intermittent?
how long have you had the disco?

the hessitation is only slight, more of a choke and cough. it is there all the time, I can accelerate through it with ease, the most smoke is when the revs rise to 2k and then back off the throttle.
also if i change from 4th to 3rd downhill , revs hanging at 2k - then accellerate, will cough and smoke then....

had the disco since august. changed oils, filters, drained sedimenter, de cat, de egr, new timing belt, new lift pump, new leak off pipes, did valve clearences.. hopefully i'l get some time to tinker at the weekend, possibly not though with the old christmas thing going on!

thanks for your time

nrgserv · Dec 15, 2010

whats the mileage on the engine?
does it breathe? (remove oil filler cap with engine running, should be little or no visible vapour coming out, place hand over hole, there should be little or no pressure)
atm i'm going with an unburnt diesel issue, possibly caused by lack of compression. cant explain why it does it at only 2k and ok with rest of rev range.
does it have edc on the injector pump? (edc-3 wires going to rear of pump(not on top of pump), non edc has 1 wire going to back of pump)
if you wanna google this bit more, type fuel cut off solenoid 300tdi.
will think on it and come back.

edit-edc, electronic diesel control. part of the immobiliser circuit and i beleive alters the advance / retard of the injection. not been inside one yet, so not 100%

reddwarf · Dec 20, 2010

Hi, may or may not help but I recently had a problem with my RR 300 tdi.

Accelerated and it coughed and ran out of puff at between 2000 and 2500 rpm.

Kept my foot down as I was trying to overtake someone and she suddenly fired up and left the road behind covered in smoke.

Afterwards just ran out of breath at about 2500 rpm.

Eventually cured by replacing the fuel filter and lift pump at £20 the pair.

Not sure which was the culprit or if they both contributed but fine now.

filfan · Dec 22, 2010

my 2.5 td smoked white smoke like a good en when i got it. thought it was the head gasket or an valve stem oil seal. when i got the head off turned out I had a bent conrod. am guessing who owned it before must have gone swimming and hydrolocked the piston. new conrod and pistons cured it until my cylinder head gave up.

Oil Leak · Dec 26, 2010

thanks for replies
merry christmas
i havn't had a chance to look at her yet, too much snow and xmas getting in the way.
to answer Q's - it's done 134k, it's non edc

Testing injectors whilst on vehicle.

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