Compression Test Injector Adapter for 1.6 Mk2 Engine???

[ftm1776]

So what is the consensus here?

Can I just use the HF injector adapter, as is, and get useful results?? Can I just add, say 50 psi, to my reading and get a good ballpark figure??? I just had a shop give me figures of 400, 400, 360, 460 for cylinders 1 through 4. They said the low #3 might just be an odd reading from valve seat carbon; so drive it and see if it clears up.....so I'd like to do the test myself rather than take it back $$$$$$.

I understand your discussion of how the small volume of the chamber is affected by what is added when using the injector adapter.

I have the "newest" #93644 HF kit. It has 21 pieces including 2 injector adapters and 2 copper washers. I will get some photos up soon. One could not fit a standard wooden pencil into it as we see above. The diameter has been reduced. The hole on the non-threaded end is only about 3/16 inch in diameter. It seems to me that the unwanted volumes could be mostly plugged with small diameter plastic tubing or washers under the Shrader valve to minimize erroneous compression reading. How about filling it with something like epoxy and drilling a hole through it?? Someone mentioned filling it with lead??

Besides, doesn't the volume of the hose also add to the volume of the TDC position? Do we have to add that in also???

[TylerDurden]

I use what must be a HF adapter... it came with one of my cars. I'm not too concerned, but the discussion raises some interesting questions.

The volume of the cavity in the adapter could be compensated for by the gauge, but I doubt a HF tester would be that clever.

WRT the hose: I believe since the check-valve is at the beginning of the hose, after a couple of strokes the hose is at cylinder pressure and its volume is no longer a factor in the reading.

A calibration check of the HF tester would be best, but until there is a comparison, I'd add 50psi as a guesstimate.

[ftm1776]

Here's the 93644 HF kit purchased in Portland, OR on 05/22/14. All pieces showing.






Here are the two injector adapters that come in the 93644 that I bought at HF on May 22, 2014. VW on right, of course.




VW adapter bore.  A standard wooden pencil will not fit in it. Opposite end has 1/8 NPT (5/16" bore)for the "Schrader" valve. Total adapter length is 2"; 3/4" @ 5/16 and 1 1/4" @ 3/16".
 


Tyler, I concur that once the hose is pressurized and sealed off by the Schrader, it should not add to the TDC volume nor affect the pressure reading for our purposes. Good point.

[TylerDurden]

^That's a lot of kit.

Reducing the bore might be useful, but I'd just calculate the extra volume and add the resulting value to the reading.

IIRC, the combustion chamber volume is around 17.3cc. Well hell...

((76.5mm/2)² * 3.14) * 86.4mm = 397cc
397/23 = 17.3cc


Let's say the adapter volume is 2cc...  2/17.3 = 12%

400 * .12 =  48psi

[ftm1776]

Yeah...all for $30 !!!

If I use it once, rather than taking the beast into the shop, it pays for more than itself.

 Thanks for the calculation.............I just call it 50 for easy remembering.

I hope someone does the experiment to compare relative readings using combinations of components, injector or glow plug adapters, etc.

Probably easier to do with the pump off.

Say, I've changed the glow plugs, but I'm wondering if there is enough room in there to use the glow adapter rather than the injector adapter without taking the pump off.

Any comments?

[92EcoDiesel Jetta]

Yeah...all for $30 !!!

If I use it once, rather than taking the beast into the shop, it pays for more than itself.

 Thanks for the calculation.............I just call it 50 for easy remembering.

I hope someone does the experiment to compare relative readings using combinations of components, injector or glow plug adapters, etc.

Probably easier to do with the pump off.

Say, I've changed the glow plugs, but I'm wondering if there is enough room in there to use the glow adapter rather than the injector adapter without taking the pump off.

Any comments?

Why don't you do the experiment? You have the HF kit. You only need to do it on one cyl for comparisin. Glow plug #4 is easy to access w/o removing IP.

[ORCoaster]

I was hoping someone would remind him of his task.  Using the GP adapter is fine on the #4 cyl but it is actually easier to pull the injectors and measure.  Beats taking the IP off.  And yes one cylinder of comparison purposes is fine. 

Just remember that when taking the injectors out or putting them in the you ALWAYS are pushing at the edge of the head and not pulling away from it.  I have a really nice head in the shed but the injector boss on #1 is snapped off.  Then replace the injectors with a slight dab of anti sieze for the next time you need to take them out. 

Waiting on numbers. 

[92EcoDiesel Jetta]

...
VW adapter bore.  A standard wooden pencil will not fit in it. Opposite end has 1/8 NPT (5/16" bore)for the "Schrader" valve. Total adapter length is 2"; 3/4" @ 5/16 and 1 1/4" @ 3/16".
 

You must have a really fat standard wooden pencil  Maybe it's an optical illusion but pic of your ruler says the diameter of the hole is a little more than 3/8". 3/8 is 0.375". I measured mine with a vernier caliper at  0.33". I see no reason why HF would change their production machinery to make that hole smaller. Please measure yours with a vernier caliper.

[ftm1776]

92EcoDiesel Jetta ,

Those are 1/16 inch graduations on the rule!!! They look pretty plump though in the photo!!!!

3/16 diameter bore

My thought was that it was redesigned to fill some more of the volume.

[ftm1776]

Just remember that when taking the injectors out or putting them in the you ALWAYS are pushing at the edge of the head and not pulling away from it.  I have a really nice head in the shed but the injector boss on #1 is snapped off.  Then replace the injectors with a slight dab of anti sieze for the next time you need to take them out. 

Waiting on numbers. 

I'm not clear on your cautionary note above. Please clarify if you would. I have had the injectors out of my 78 Rabbit but that was a long time ago and so I appreciate you warning.

On my current car, which has recently had the injectors rebuilt by DFIS in Portland, OR, I see the copper anti-sieze that has squished out around each injector.

I'll try to get around to generating some numbers...............

[TylerDurden]

I'm not clear on your cautionary note above. Please clarify if you would. I have had the injectors out of my 78 Rabbit but that was a long time ago and so I appreciate you warning.

It's easy to break the threaded injector bosses by pulling the wrench handle toward the radiator. Better to push the handle toward the windshield and hold the extension steady with the other hand.

[92EcoDiesel Jetta]

I'm not clear on your cautionary note above. Please clarify if you would. I have had the injectors out of my 78 Rabbit but that was a long time ago and so I appreciate you warning.

It's easy to break the threaded injector bosses by pulling the wrench handle toward the radiator. Better to push the handle toward the windshield and hold the extension steady with the other hand.

I don't think pulling or pushing matters, what's important is adding an equal counter force on the other end. To be sure, use a T bar, or an impact gun.

[92EcoDiesel Jetta]

92EcoDiesel Jetta ,

Those are 1/16 inch graduations on the rule!!! They look pretty plump though in the photo!!!!

3/16 diameter bore

My thought was that it was redesigned to fill some more of the volume.

It is 1/16! So HF did decrease the bore so instead of 50 psi off, it is 30 psi off. They could have made the hole 1/16 so it's 5 psi off but that would mean using more steel.

[ftm1776]

Tyler & 92 ECO,

I get it.............no side-load; only torque on the injector body.

[ORCoaster]

If the injectors have been out recently a T handle works fine but on some of these engines you are removing a part that has been in place for at least several decades.  Think Barn find.  I use a breaker bar and make sure I am positioned on the injector correctly and swing towards the engine or windsheild on the proper plane.  I keep my left hand on the extension and socket, 27 mm, on the injector and give a short snap with my right on the breaker bar handle.  I find all VW threads repond to a snap versus a slow increase in force to make then come free. 

I think others have described it well enough for you.