Injector Leak-off Test

[skwoodwiva]

This is my 2nd of 3 runs. 2 runs for 10 sec, & 15 for final.
I use 1/8 id edit- less than, silicone. 4" equals 1ml (measured).

The 1st, through out, the 3rd, I filled each "well" where the orig fitting sits to the brim then when inserting the hose the level would come up about 1/2 to 3/4 " so each was marked as zero.

I spite of #4 being so much out of the pack it is still only edit, 1.1ml or so ml for 15 sec. In the 1st pic 10 sec it is about 1 ml.

Edit actually, test 1(10 sec), comparing to 3 (15 sec) is right on. .7 ml for # 4 injector

Note being such a small ID the scale is way exaggerated.

Has anyone cleaned their bad ones w/ some of the purge products & repeated the test? Like Wynns, BG or Liqui Moly.

 

[Midwestdrifter]

Leak back is caused by internal wear. I doubt any cleaning will work.

 

[skwoodwiva]

Thanks MWD.
More…
I used a 1ml monojet & its not 4" but 5 3/4 " per ml! Thats .67ml for 10 seconds for #4.

 

[hkpierce]

I use a needle nosed pliers to remove the clip and then use the same pliers to gently pry the T fitting up. No broken ones yet!

I found that the same pliers used to remove and reinstall the glow plug wiring (such as such as Assenmacher SPR0558 or similar) worked well. They grab on the head of the plastic fitting and there is no pressure on the arms that may break them. Grip with the left hand and leverage up with the right hand.

 

[jimmyhorns]

Leak back is caused by internal wear. I doubt any cleaning will work.

Leak back is part of the design of the injector and occurs from new.

Excessive leak back is a result of multiple things, wear being one of them, however things like a dirty nozzle, clogged nozzle, and dirty / sticking needle will also cause excessive leak back.

I've just had an injector out, disassembled and cleaned the nozzle / needle assembly, and my leak back from the cleaned injector is about 50% that of the other 3 injectors, and within spec. The nozzle and needle were gummed / carboned up to some extent, and this appears to have helped both with the spray pattern (now normalised) and the leak back. This is an NVC3 but the principle is the same.

 

[Midwestdrifter]

Thanks for the info. The NCV3 design is a bit different due to the piezo actuator, but the lower half is basically the same.

 

[Jan M]

No need to go OEM on these. If you can wait, this kit from the UK is a good deal:
http://www.ebay.com/itm/281466773901

View attachment 119716

I ordered these yesterday as a precaution before doing the leak-off test. 39£ including international shipping.