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+--- Thread: Compression and leak down testing (/showthread.php?tid=1805)
Compression and leak down testing - ForcedInduction - 10-02-2010
Continuance from here: http://www.superturbodiesel.com/std/new-project-skunkwerks-em9d-t-858-10.html#pid18367
(09-30-2010, 12:48 PM)turbodeezl Do you have a link that shows what this tester looks like?Its just a pressure regulator with two gauges and an 0.040 orifice between them.
![[Image: 94190+leakdown+tester1216255403.jpg]](http://forums.pelicanparts.com/uploads13/94190+leakdown+tester1216255403.jpg)
The one I built is exactly that. I used a -4 JIC 45 so it will attach with a hose to the glowplug fitting that comes in the harbor freight compression tester kit (with the schrader valve removed). The fitting in between the gauges was tapped for a 1/8NPT plug and drilled to 0.040".
The HF compression tester was altered to remove the swivel fitting that always leaks after the first use and to extend the hose so its readable while cranking.
I'm in the middle of moving this weekend so it won't be until the 9th at the earliest before I can test it.
What I really want to do is disable a cylinder and test operating compression, specifically how much the engine produces at boost. Mainly for curiosity but it will also help me get a more accurate estimate of the engine's volumetric efficiency.
RE: Compression and leak down testing - turbodeezl - 10-10-2010
would it be possible to modify to connect on 1 injection line to determine pump pressure on each ouput nozzle of the injection pump?
RE: Compression and leak down testing - ForcedInduction - 10-10-2010
No.
RE: Compression and leak down testing - ForcedInduction - 10-10-2010
A little back history;
The 300D has a slightly rough hot idle and nailing on #5.
Compression Cold/Hot
1- 300
2- 330
3- 340
4- 335/360
5- 250/275
The 240D has a knock in #1 and low compression in #2.
Compression cold
1- 340
2- 225
3- 340
4- 345
5- 345
The 300D tested 25%@100psi for the #5 cylinder. There was a little going past the rings (expected) but the rest was leaving the exhaust, I could cover the tip and it would pressurize the exhaust system pretty quick. I rotated the engine to double check and it repeated. Checked with #4 and it was 80%@100psi with only some blow-by.
The 240D tested 65%@100psi on the #2 cylinder. A tiny bit going out the intake and the rest in blow-by. Looks like the cylinder is just plain worn or there is a broken ring.
Note: For leak down testing, 100psi is the pre-orifice line pressure and the pressure trapped in the cylinder post orifice is represented as a 0-100%(psi) seal. 100% would be perfectly sealed (impossible) and 0% would be a catastrophic leak (or testing on the intake/exhaust stroke).
I check for TDC@compression by holding the hose to my ear and slowly rotating the engine until I turn it a hair further and no air comes through. Its a safer bet to be a touch past TDC than before, in case the engine rotates from the pressure it won't turn the timing chain backwards.
Looks like its time for a valve job on the 300D this winter!
RE: Compression and leak down testing - ForcedInduction - 10-10-2010
Tried to do a running compression test with the injector line routed to a bottle but the cheapass Harbor Freight fitting's schrader valve failed at 500psi.
RE: Compression and leak down testing - turbodeezl - 10-13-2010
(10-10-2010, 07:02 PM)ForcedInduction Tried to do a running compression test with the injector line routed to a bottle but the cheapass Harbor Freight fitting's schrader valve failed at 500psi.
If the compression checks out, I'm assuming any nailing would be the result of the injector(which one can pop-test) or the injection pump. Is it possible?/how likely? for one nozzle of the injection pump to not put out enough pressure?
RE: Compression and leak down testing - ForcedInduction - 10-13-2010
Its not related to the injection system.
RE: Compression and leak down testing - Captain America - 10-15-2010
Does anyone know how low the compression could be before the engine would not run? Would super low compression cause hard starting but then not be as noticeable once the engine was running? I need to check my compression...
RE: Compression and leak down testing - ForcedInduction - 10-16-2010
The OM616 in my 240D had 220-250psi on all 4 and wouldn't even fire with ether.
Bonus note: The tow truck in the background threw a rod on new-years night as I was pulling the 240D's chassis home.
RE: Compression and leak down testing - Captain America - 10-17-2010
Shit so that could be my main starting issue .... waaaa. Im gonna go cry now.
RE: Compression and leak down testing - willbhere4u - 10-17-2010
Hell I bet that my old 240d auto has less compression than that it has 15psi oil pressur at 4-5k about 5 at idle no knocking and has so much blow by that it come out of all of the engine seals it smoke more out from under the hood than the exhaust!
I have had people tell me at stop lights my engine is on fire!
It stars easily in warm weather it cranks over so smooth and fast a lot more than any of my others and when you shut it off it just slows down it shuts off like a Gasser! You could probably get out of the car and watch it slow down till it stops very smoothly
But I'll have to test it when I put my turbo motor in there! maybe I can rig it up with a generator or something!
RE: Compression and leak down testing - garage - 10-17-2010
(10-17-2010, 01:02 AM)willbhere4u I have had people tell me at stop lights my engine is on fire!
Isnt that the best!!hahahah
RE: Compression and leak down testing - Silberpfeil - 10-17-2010
(10-10-2010, 05:55 PM)ForcedInduction
Note: For leak down testing, 100psi is the pre-orifice line pressure and the pressure trapped in the cylinder post orifice is represented as a 0-100%(psi) seal. 100% would be perfectly sealed (impossible) and 0% would be a catastrophic leak (or testing on the intake/exhaust stroke).
I check for TDC@compression by holding the hose to my ear and slowly rotating the engine until I turn it a hair further and no air comes through. Its a safer bet to be a touch past TDC than before, in case the engine rotates from the pressure it won't turn the timing chain backwards.
Looks like its time for a valve job on the 300D this winter!
know how long for a valve job on a 617.952? Book time? Your time FI?
RE: Compression and leak down testing - ForcedInduction - 10-17-2010
(10-17-2010, 06:13 PM)Silberpfeil know how long for a valve job on a 617.952? Book time? Your time FI?
I don't have a standard job time book and I don't have the place to do a valve job myself. I'll have to see how much Tom Judd or Stu Ritter will charge.
RE: Compression and leak down testing - turbodeezl - 10-21-2010
(10-13-2010, 06:52 PM)ForcedInduction Its not related to the injection system.
When I first start my '91 300D on a cold morning, I get 'zero' nailing while the glow plugs are still hot, but nailing starts after they go off within a minute or so. What do you thinK?
RE: Compression and leak down testing - ForcedInduction - 10-21-2010
Compression and/or timing.
RE: Compression and leak down testing - Silberpfeil - 10-23-2010
(10-17-2010, 06:13 PM)Silberpfeil know how long for a valve job on a 617.952? Book time? Your time FI?
(10-17-2010, 08:37 PM)ForcedInduction I don't have a standard job time book and I don't have the place to do a valve job myself. I'll have to see how much Tom Judd or Stu Ritter will charge.
If you would let me know please (when you get it done) how long it took and how much it cost?? I'd appreciate it.
Thanks,
John
RE: Compression and leak down testing - winmutt - 10-25-2010
(10-21-2010, 06:46 PM)ForcedInduction Compression and/or timing.
/injectors.
RE: Compression and leak down testing - gsxr - 10-30-2010
(10-21-2010, 12:55 PM)turbodeezl When I first start my '91 300D on a cold morning, I get 'zero' nailing while the glow plugs are still hot, but nailing starts after they go off within a minute or so. What do you thinK?That's somewhat normal, as long as the "nailing" isn't severe, and goes away when the engine is up to temp. Otherwise you should check the timing chain stretch (known problem on early 90's OM60x engines) and IP timing to start with. If the "nailing" is severe and/or present with a hot engine, pull the injectors and have them pop tested. I've heard the increase in diesel klatta when the afterglow shuts off on a cold morning, but on my cars it was just the normal diesel sound. It should go away if you increase RPM's, even when cold.