Renault grand scenic 1.5 dci injector knock - johnkent

I want to do a leak back test as i have got loud diesel knock and smoke

I have bought 3mm clear tubing and 4 water bottles

thing is when i look at the leak back pipes if i take the clip out and prize the connestor out the hose doesnt look like it'll go in properly.

Can anyone talk me through the procedure of doing a leak back test to identify a dodgy injector

Ive googled /you tubed it it and nothing on my engine

Thanks

Edited by johnkent on 10/03/2017 at 19:31

Renault grand scenic 1.5 dci injector knock - focussed

The leak back test isn't going to tell you a lot if you have already diagnosed that you have an injector problem - best whip all four out and take them to your local diesel shop and get them sorted out and set up.

Renault grand scenic 1.5 dci injector knock - hardway

Your supposed to use adapters in the kit you haven't bought!

Anyhoo,

The injectors are linked via little pipes.

if your real careful you can remove these tubes and connect up your pipes,

you'll need to blank of the other outlets on the "T" connector on the injector and the return pipe or diesel goes everywhere.

Run your fitted pipes to the bottles,

Cable tie these bottle to a plank to secure the as the engine is running.

Start it up and monitor the levels.

Bad injectors usually show up as an obvious greater level.

But the norm is if any level is more than 5% more than the other it means injevtor out and bench tested at a specialist.

I've actually done all this at a roadside breakdown and I'd forgot my tester kit so it does work.

Renault grand scenic 1.5 dci injector knock - Railroad.

As already stated. Diesel knock is caused by a poor iinjector spray due to a worn or partially blocked nozzle. A leak back test will not show this or enable you to cure it. A diesel specialist will be able to test your injectors and overhaul them.

Renault grand scenic 1.5 dci injector knock - johnkent

It hought by doing a leak back test you could identfy a bad injector, rather than whipping them all out and getting them bench tested

I'll give the leak back test a go first then see what results i get

Ive ordered the proper kit just to be sure of not breaking any connections

I'll try and post a video of what its doing i'm pretty sure itsa bad injector or injectors

thanks for your replys i'll post an update

Renault grand scenic 1.5 dci injector knock - gordonbennet

Don't you long for the old days of indirect injected Diesels and mechanical pumps, which given a bit of looking after lasted indefinately and were the most reliable engines ever made.

Suspect injector? remove injectors which would take about 20 mins cos basically they were in the same sensible place as spark plugs would be on a petrol (so any injector seal leak didn't mean carbonised oil leading to eventual engine destruction), nip 'em over to the local Diesel shop who'd clean and test them and if necessary rebuild them.

Last set of injectors i had to remove was on my Renault 21, easy to work on, cleaning and testing the set cost me the princely sum of £40, so about £120 today.

Renault grand scenic 1.5 dci injector knock - johnkent

i might do that, just didnt want to take all 4 out in case they are hard to get out.

On the leak back test, all i do is disconnect leak back pipes block them off connect 4 tubes from the injectors run car for a minute anything under 40mm in pots is ok anything excessive over that indicates faulty injector

Is this the correct procedure or am i missing something

Thanks for any advise

Renault grand scenic 1.5 dci injector knock - hardway

Not as easy as that,

Basically they all should leak back the same amount,

No more or less,

Either means a possible fault.

A scan with Renaults can clip will give an injector correction figure,

that will point to an injection correction factor that "could" account for the smoke.

And remember Renault number their cylinders from the gearbox end so THAT'S # 1 cylinder.

So be very careful if you get a fault code for say cylinder #2 that you go to the right cylinder injector.

in this case that would be the 2nd cylinder in from the gearbox.

Renault grand scenic 1.5 dci injector knock - johnkent

cheers mate

can you reccomend a renault can clip

im selling the car so want to do this as cheap as possible

Renault grand scenic 1.5 dci injector knock - hardway

"Can Clip" is Renaults own diagnostic program.

You can get them on Ebay but try you local diesel specialist for a scan.

Will cost less.

Renault grand scenic 1.5 dci injector knock - johnkent

thanks mate

Someone has suggested it might be glow plug related would the knocking and smoke appear with dodgy glow plugs ?

Also theres no EML on

Would a dodgy injector throw the light up ?

cheers

Renault grand scenic 1.5 dci injector knock - johnkent

Or even the EGR valve sticking

Anyone any ideas

Renault grand scenic 1.5 dci injector knock - Railroad.

A stuck EGR valve won't cause diesel knock. A jetting or hosing injector will.

Renault grand scenic 1.5 dci injector knock - hardway

As railroad stated diesel knock is simply either incorrect timing or much more common is too much fuel from a failed injector.

Or if you wish to replicate "knock" just listen as some b***** sprays starter fluid into an intake.

Chills my blood!

You only use the smallest amount of fluid.

Anyway the real reason for all this technology on vehicles is very simple.

Correct diagnosis.

A scanner of the correct type plugged in and the correct knowledge/experience will give indications of where/what the fault may be.

So you scan it and read on the live data the injector fueling correction values.

Or the more expensive way is remove all injectors and send them of for testing.

Scanning it make financial sense,

it may be theres only one outstanding correction value so THAT is the only injector removed and tested/replaced.

SCAN IT!

Renault grand scenic 1.5 dci injector knock - johnkent

heres what it sounds like

www.youtube.com/watch?v=xKOvUaPIKHM&feature=yo...e

Renault grand scenic 1.5 dci injector knock - csgmart

Blimey - quite a noise.

Renault grand scenic 1.5 dci injector knock - Railroad.

That's not diesel knock either. Sounds more like camshaft or a piston hitting a valve. By the look of the pattern of the exhaust gas it looks like the engine is misfiring.

Renault grand scenic 1.5 dci injector knock - johnkent

The smoke out the back is definately unburnt fuel no codes or lights on dash

Cant see it be a piston hitting a valve as the engine would of chewed its self up by now

 

Ask Honest John

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