TD4 Injector leak off test

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Dutchjohn

Dutchjohn

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Just wanted to check the correct way to do a leak off test on the TD4 injectors. According to one post by Chaser, the test is carried out without cranking the engine, just using pressure from the electric fuel pumps. However, according to RoverRon, the engine should be cranked with the injector and crankcase sensor plugs disconnected.

Does anyone know which is correct because I get different results using the two methods? :confused:
 
Both ways are right but test with different pressure. If you are going to test while cranking the important thing to remember is to disconnect the injector electrical connections to make sure the injector remains closed.

Testing with ignition on gives about 35psi for the test on the seals, if you test while cranking you have massively more pressure and risk someone getting a face full of high pressure diesel.
I guess the safest way is to test with ignition on only first (which should be enough to show an injector that won't seal) then if you like try with the high pressure pump rotating while cranking. :)
 
Chaser said:
Both ways are right but test with different pressure. If you are going to test while cranking the important thing to remember is to disconnect the injector electrical connections to make sure the injector remains closed.

Testing with ignition on gives about 35psi for the test on the seals, if you test while cranking you have massively more pressure and risk someone getting a face full of high pressure diesel.
I guess the safest way is to test with ignition on only first (which should be enough to show an injector that won't seal) then if you like try with the high pressure pump rotating while cranking. :)
Click to expand...

Thanks Chaser, carried out test using both methods. No sign of anything when testing with ignition on, but plenty widdling out of 3 injectors while cranking. That mean they are in need of attention?
 
Dutchjohn said:
Thanks Chaser, carried out test using both methods. No sign of anything when testing with ignition on, but plenty widdling out of 3 injectors while cranking. That mean they are in need of attention?
Click to expand...

It really depends on the amount leaking back. Only change if you have bad starting or other clearly injector related symptoms.

If they were leaking with just low pressure then it's easier to say a definite yes...
 
Chaser said:
It really depends on the amount leaking back. Only change if you have bad starting or other clearly injector related symptoms.

If they were leaking with just low pressure then it's easier to say a definite yes...
Click to expand...

Starting is definitely iffy considering she used to start on the button every time. Also there's a fair amount of black smoke when accelerating. Once driving she pulls strongly in every gear, there are no Maf issues, the air filter is clean, intercooler hoses are new. I can only think that the tricky starting and black smoke must be injector related, just not bad enough to be really obvious. Based on your advice I'll wait and see if it gets any worse. Meanwhile, I'll try some injector cleaner and stick to a decent brand of fuel and see if that helps.
 
Sorry to hijack this thread - I'm having starting problems - works with easy-start in air intake, but that's the only way to get her going. Noticed it getting gradually harder to start recently, but now won't fire at all.
Anyhoo - tried the leakback test with just fuel pump pressure and couldn't see a problem- one injector (second from the left) perhaps had a bit of a dribble (bit like when a glass has been filled to the brim) but definitely not ****ing out.
Not being in possession of a kit and being on my own I couldn't really do the test while cranking, but I think I'll need to get some assistance and some tubing and giving the test while cranking a go.
If this reveals an injector fault where's the best place to go? New or recon?
If not what else could be the problem? Have read it could be a rail pressure sensor, crank position sensor - any way to check specifically for these?
Advice appreciated.
N
 
when using the ignition only will not cause fuel to pour out, if it is just slowly flowing out under around 6 seconds then that will be the faulty injector. If its not starting from cold or walm, would put my money on it being that injector. For me I would get it refurbished, where we take ours the cost is £55 to sort out the leaking back or £68 for a full refurb both plus vat. Dont know the postage cost as we drop them off, its a same day turn round.
 
Thanks for the info booboodag - will try the cranking method when I've some time.
If you're happy to recommend the place you use I'd be grateful if you could PM me their details - may as well use somewhere that comes recommended rather than chance it elsewhere.
Cheers
 
Another thing I should mention is that it's an auto (2004) I maybe wrong, but I think it's a different injector model to the manual gearbox (why, I don't have a clue) but would this affect the ability to recon/refurb?
 
Removing the plug on the high pressure commonrail contact and clean/spray the contacts it might be of help ??
 
Ok gave it a test with cranking the engine. Was expecting diesel to be spurting out of the faulty injector(s) - not so. More of a tiny dribble - they only just began to fill up the small hole where the leak off pipe is inserted.
All 4 of them began to fill after quite a bit of cranking (was advised to turn over for at least 20 secs). Difficult to say for sure but I thought 3 of the 4 filled up quicker than number 1 injector.
So, in the absence of diesel fountains, does it sound like I have leack back problems on all 4?:eek:
As mentioned - difficulty in starting, but once going (with easy start) all seems fine. Would this tiny amount of leakage be the cause? Should they be absolutely bone dry in order for there to be no problems?
This is begining to sound like a costly job now - especially if any of em are reluctant to come out (which no doubt they will!)
Cheers
N
 
when you do a leak back test what do you do about the diesel coming out of the black pipes connected to the top of the injectors ? i pulled clip out removed the plasitc connector and when i turned ignition on diesel cam ****ing out what does that mean ?
 
Did a search and found this thread that finished without a answer to the question , which is the same question I have , ie

should diesel pour out the spill return pipe when doing the ign on (ie not cranking) test , even though it is disconnected from the injectors?
 
Could be low pressure fuel pump listen for it behind wheel arch liner drivers side rear. Or fuel filter.
 
Check glow plugs disconnect the plugs, run a lead from the live side of the battery just touch the top of each plug
With the live wire, the ones that spark are ok the ones that don,t are u s
 
Also if all spark and are ok make sure you have got power going to them with a tester when the ignition is first turned
On
 
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