How to do compression test on 3B? (1 Viewer)

Joined
Sep 11, 2020
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Leverkusen , Germany
Hi there
I would like to test the compression on my 3b engine. It has 306.500 km on it.
It fires up and runs really nice, though, although it has quite significant blow-by, think. (I however lack any comparison and experience to really tell).
But I'm a bit concerned as my engine oil appears to get thinner only after 2000km from last change. Can't really tell whether it's getting more.
No issues with withe smoke, oil in coolant or cappuccino cream on oil, so rather not a head gasket issue..
Did a chromatography on the oil and it appears to have diesel in it..
Did an oil change (now with level exactly known to monitor whether it's getting more).
I'm thinking of worn piston rings or bore. That's why the compression test...

Manual says: Compression test trough glowplug seats. Well... Ok. Meter can be borrowed.
For testing, fuel injection has to be cut. Engine must not fire...
But my Question:
- How to best cut fuel in an easy and secure way?

There is no fuel cutoff solenoid but this witchcraft EDIC. Cutting power to this leaves it in default RUN-position, I believe, where engine can fire, still. Same with cutting the oil sensor. Can I force it's position to Stop by any means, and would that be sufficient?
- Any other suggestions how to cut fuel injection for compression test the easy way?

Thanks for advise
Best regards
Felde
 
Joined
Oct 2, 2015
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Las Vegas
@Felde , You said the engine fires right up... that would indicate to me, the compression is good.
But if you want to know exactly what you have compression wise...like the manual says, remove the glow plugs/heaters.... and do the test.

I am getting out of my lane here, since I don't own a 3B. But if you remove/disconnect the fuel line to the Injection Pump & then start the engine, and let the engine die out due to fuel starvation. (Then secure the fuel line to the Injection Pump so fuel isn't pouring / dripping around the floor of your garage or driveway afterwards). I think you will be good to go for your compression test. (you will probably have to re-bleed your fuel system after the compression test, though).

Hope you figure it out. Keep us posted.
 
Joined
Jul 22, 2003
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18,365
Location
Perth Western Australia
I think on the 3b you cut the power to the edic so its stuck in the off position.. On some diesel engines the diesel leaks past a seal that separates it from the engine oil
I don't think the diesel from the injectors would get it into the oil unless an injector was stuck open. And once the engine is off, it stops pumping.
Easy starts with all cylinders firing is not usually a sign a of a bad engine. Quite the opposite.
 
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Joined
Sep 11, 2020
Messages
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Leverkusen , Germany
On some diesel engines the diesel leaks past a seal that separates it from the engine oil

Thanks for any hint.
Can you be more specific where that seal would be? Engine or injector pump?
I found a thread in the web saying that also an injector pump may internally leak diesel into the oil. But how the hell to diagnose this?!
 
Joined
Jul 22, 2003
Messages
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Perth Western Australia
Its got to be where the injector pump joins the engine. Every diesel has one. You need a diagram from the workshop manual.

Usually you keep an eye on the oil level. You could pull the injectors and get them tested. If they come back clean, it has to be leaking past the pump.

You can also disconnect the rod from the edic to the pump
 
Joined
Dec 7, 2019
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502
Location
North Carolina, USA
My BJ73 has a fuse in the fusebox labled "engine" . When I take that fuse out the fuel cutoff will not "open" and the engine will not start. I removed that fuse which allowed me to crank the engine without fuel flow when I did my compression test.

I'm not familiar with your engine IP configuration. It sounds like you don't have a electric fuel cutoff solonoid. If you have a Idle screw then you can unscrew it until the engine dies/it won't run without pushing the accelerator. (You may have to loosen your throttle cable as well.) That should enable you to crank the engine with the starter without giving enough fuel to fire so you can do your compression test.
 
Joined
Sep 11, 2020
Messages
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Location
Leverkusen , Germany
Hi all
Thanks for the ideas and advise. Cutting off the EDIC via fuse sounds great, provided it stays at stop position. As several people mentioned: Default is Run position, so I may have to force it to stop position. If it doesn't work a different way I'll disconnect the rod. I will test then before pulling the glowplugs. If it doesn't fire up, all good.
I will for sure pull all glowplugs at once then.
I have to wait for the test device. Maybe I get it next week.

Happy Thanksgiving everyone!
 

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