Diesel knock when reving after start up

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DaveM-sport

DaveM-sport

Active Member
Posts
847
Location
Cork, Ireland
Sorted my TD5 after the injectors failed and blew my headgasket. Got them fully refurbed and he also put slightly larger nozzles on them given that my engine is tuned abit.

Stuck them in, coded them and fired it up and it runs very nicely and really smooth in fairness. Only trouble is if it's reved hard with a good blip of the throttle not long after start up, it has a diesel knock and will die and cut out. If go to start again straight away, it's almost like it's out of fuel.

If well warmed up and revs are brought up and down gradually and then try the same again, it won't knock at all and runs perfect.

Maybe a fuel pressure delivery issue after start up or maybe injector washers aren't after sealing right?
I'll have a fuel pressure guage connected up in a few days at least so will be able to check pressure from the pump and at the regulator that might rule those out.
 
Does yours idle ok?
Start it, let it sit at idle for 10 mins, should be ok, if it slows and stops its a flag that the copper washers may not be happy.
Make sure the mating faces are spotless.
Also, mine idled ok after a major rebuild, but as soon as I started to pull away, it started knocking/smoking, the heavy white smoke of unburnt fuel.
One of my (newly rebuilt) injectors had failed.
Never heard of larger nozzles, that could be the issue, if the injectors are putting more fuel in, possible at the wrong time, it will cause knocking and white smoke.
The injector coding may be irrelevant now, as the injectors have been modified.
You may need to have your ECU remapped to suit.
Mark
 
Try annealing the washer mate!
And like marko said makesure the seating faces are spotless
 
the fuel pump in the tank should be screaming like a cat if it was copper washers

since the head has been removed check the timing it could be one tooth out
 
It idles perfect. Left it running for about 15 minutes once was happy with it to fully warm up while I made sure cooling system was bled fully

There's no white smoke, just black when give it a shot of throttle.

I have another set of new injector washers so I'll anneal those and see if they make any difference.

It already has a map by Alive to suit the mods albeit with standard injectors.

Mods are bigger Intercooler, VNT turbo, EGR, cat delete and center box delete, k&n filter but safari snorkel.
Few other bits then like silicone hoses, MANN catch tank and little bits like that.

It probably has pretty high compression due to new oversize pistons and a decked block from the full rebuild last year.


Timing is definitely right. I'd time one of these things with my eyes closed at this stage lol. Just to be sure as it's a little harder with just the head off rather than block and head together on a stand the first time I built it last year, I made sure the crank and cam was locked this time by making up pins. Coloured links then on top of the chain and clyinder one at tdc by checking through the injector holes and cam lobes off the valve followers just to be sure.

I might try its old map on it and see if that makes any difference too and if it does, get on touch with Alive. Ideally, it could do with a live remap rather than uploading a generic tune to suit the engine spec on paper.

Due to the higher cr and bigger pistons, I'd imagine the larger nozzles wouldn't be any harm once it's mapped to suit.
 
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If your happy with the mechanical timing (and its actually difficult to get wrong) then the actual injection timing or the injectors, sound wrong.
Injection timing on the TD5 is controlled by the ECU.
Just to check, did you double check your injector rocker clearances? i.e. at full lift, screw the adjustment screw down until it bottoms out then back off 1 turn.
 
DaveM-sport said:
It idles perfect. Left it running for about 15 minutes once was happy with it to fully warm up while I made sure cooling system was bled fully

There's no white smoke, just black when give it a shot of throttle.

I have another set of new injector washers so I'll anneal those and see if they make any difference.

It already has a map by Alive to suit the mods albeit with standard injectors.

Mods are bigger Intercooler, VNT turbo, EGR, cat delete and center box delete, k&n filter but safari snorkel.
Few other bits then like silicone hoses, MANN catch tank and little bits like that.

It probably has pretty high compression due to new oversize pistons and a decked block from the full rebuild last year.


Timing is definitely right. I'd time one of these things with my eyes closed at this stage lol. Just to be sure as it's a little harder with just the head off rather than block and head together on a stand the first time I built it last year, I made sure the crank and cam was locked this time by making up pins. Coloured links then on top of the chain and clyinder one at tdc by checking through the injector holes and cam lobes off the valve followers just to be sure.

I might try its old map on it and see if that makes any difference too and if it does, get on touch with Alive. Ideally, it could do with a live remap rather than uploading a generic tune to suit the engine spec on paper.

Due to the higher cr and bigger pistons, I'd imagine the larger nozzles wouldn't be any harm once it's mapped to suit.
Click to expand...
I'm not a big fan of adding in larger injector nozzles on a diesel unless its highly tuned like most truck drag racing do when they want to twist the chassis on take off and bellow out black smoke
the electronic solenoid on the injector is controlled via the ecu and the signal from the ecu allows the injector to stay open longer or shorter in time duration .
now that you have different injector nozzles this has changed how the fuel is atomized ..a bit like when an injector has a blocked nozzle the spray pattern is now changed

for example I took a different approach I have a LPG system installed for some extra power on the fly ..when I was setting this up I got to greedy ...... to much LPG was stalling the engine with out any valve bounce or diesel knock the thing would cut out
 
That's true. Fine on an old diesel with a mechanical pump where bigger injectors can be an advantage but not really sure how much of a gain they are on a common rail with an ecu looking after everything.


markomate2 said:
If your happy with the mechanical timing (and its actually difficult to get wrong) then the actual injection timing or the injectors, sound wrong.
Injection timing on the TD5 is controlled by the ECU.
Just to check, did you double check your injector rocker clearances? i.e. at full lift, screw the adjustment screw down until it bottoms out then back off 1 turn.
Click to expand...

Yup, injectors clearances all done when fitted them. It's pretty much idiot proof to mess them up too really :D
I might double check them again though just in case they need to be done after its done abit of driving on the new ones or in case a nut got a little loose but unlikely as all torqued to spec.


Speckydude said:
Worn flywheels knock and vibrate, especially going into reverse.

This will help if the injector clearances need checking;

https://www.landyzone.co.uk/land-ro...w-engine-boy-does-it-clatter-when-cold.99678/
Click to expand...

New flywheel and clutch fitted when I rebuilt the engine so that's only about 1500 miles old.

I have a nanocom. Although, I'd have thought the balances should be almost at 0 for freshly refurbed injectors, they are all around 1-8.
 
No, didn't get new codes. Used the ones that were on the injectors already. Will find out about new ones :)

Haven't done much in the last couple of weeks as have the dash and everything stripped out wiring new lights, heated windscreen and new radio and cb and things but nearly finished that so will look into the injectors more after the weekend :)
 
Bit of an update on this. I swapped the injectors with the ones from my dad's Discovery as doing abit of work on that at the moment and needed to do the rocker cover gasket anyway.

No change at all, possibly even a little worse with new washers. Put my own ones back in again then (didn't have a second set of washers so just annealed the ones I had just fitted with the other injectors) and ran **** for a minute and then fine again as before with abit smokey when cain it and bit of a diesel knock if rev it hard with no load.
The seats in the head for the injectors didn't look amazing so going to get another set of washers and re-cut the injector seats and see if it helps any bit.
 
I have seen this happen on other engines but not the TD5 but similer engines that run cam driven injectors
the vehicle was borrowed from a friend and he/she has accidently put 10 litres of petrol by mistake (but to say thanks for lending the car ) this 10 litres mixed with the 60 to 70 litres of diesel turned out to be a ball ache
the only way I found this was I ran the engine from another fuel source

if your 100% sure the fuel is perfect.. I would suggest looking into the hydraulic lifters ..if there not operating correct this will give a wrong air ratio mix resulting also in diesel knock

other things that control air fuel ratio and my loss of compression episode

my Td5 went into decompression mode for a short while the engine would not even start engine just whizzed faster than normal sounded like the engine had zero compression ...even with spray down the air intake the engine didn't start apparently there is oil regulator located in the front of timing area that controls oil to the lifters but never looked into it as my problem never recurred
 
Last edited:
ozzyboydeano said:
I have seen this happen on other engines but not the TD5 but similer engines that run cam driven injectors
the vehicle was borrowed from a friend and he/she has accidently put 10 litres of petrol by mistake (but to say thanks for lending the car ) this 10 litres mixed with the 60 to 70 litres of diesel turned out to be a ball ache
the only way I found this was I ran the engine from another fuel source

if your 100% sure the fuel is perfect.. I would suggest looking into the hydraulic lifters ..if there not operating correct this will give a wrong air ratio mix resulting also in diesel knock

other things that control air fuel ratio and my loss of compression episode

my Td5 went into decompression mode for a short while the engine would not even start engine just whizzed faster than normal sounded like the engine had zero compression ...even with spray down the air intake the engine didn't start apparently there is oil regulator located in the front of timing area that controls oil to the lifters but never looked into it as my problem never recurred
Click to expand...

I was thinking it could well be lifters to be honest considering the knock is most evident when giving the engine a hard rev towards the redline from idle.

With the big change in rpm then, the lifters can't keep up if not operating perfect.
If build up the revs slower, it'll rev all the way to 4900 and can be held there with no noticeable issues.

Its quite a bad diesel knock and once back do idle just after the split second of high rpm when it knocks, it runs lumpy and mild miss for a moment or two.

With the head being off and the engine rebuilt last year, the lifters might be acting up with being in and out of the engine.

For changing them, can I just lift the upper cam box off and then replace the head bolts without taking the head itself off?

Don't really want to go taking the whole head off yet again :eek:
 
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