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  #1  
Old 03-11-2016, 03:40 PM
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Harbor Freight Diesel Compression Tester mod

EUREKA!

That dang blasted 90 deg elbow in the HF diesel compression tester that breaks oh so easily can be replaced with a 1/4" JIC elbow, much more stout. I paid ten bucks at the local NAPA(highway robbery) to have it in hand now, Amazon also has them for $2.45/ea and prime eligible.

Just spreading the word. This may be widely known already, I hadn't read it on these forums, but have seen complaints that the elbow breaks too easily.
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  #2  
Old 03-11-2016, 04:24 PM
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I didn't use a 90 deg adapter. Is that for testing via the glow plug holes? I used the injector holes because time to pop-test them anyway.
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  #3  
Old 03-11-2016, 05:54 PM
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Thanks for the head-up!!! I have that tester but have not used it yet. I'll Amazon that part right now.
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  #4  
Old 03-11-2016, 06:48 PM
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Is the tester worth the money? I've considered buying it but never have.
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  #5  
Old 03-11-2016, 07:08 PM
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Quote:
Originally Posted by Junkman View Post
Is the tester worth the money? I've considered buying it but never have.
I think so for the money. The gage is probably not NIST-traceable but the system works, the adaptors fit, etc. I was pleased to have mine when I wanted to check the health of my engine. It'll get you close enough that you can tell if you have "issues".

Dan
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  #6  
Old 03-12-2016, 12:05 AM
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I agree, well worth it for the money. If I was a professional diesel mechanic then no way, but that's not exactly the HF target demographic. My only concern was that elbow, which sure enough broke and was replaced with an upgraded part.

If you're not pulling the injectors for some other reason, going through the GP holes and using the elbow is easier, and no new heat shields required. This applies to the 617, no experience with other engines.
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  #7  
Old 03-12-2016, 12:21 AM
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I used it to check compression before thru the injectors. Not too bad
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  #8  
Old 03-13-2016, 01:23 AM
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The Injector adapter in the HF set has a rather large empty space in it.

While the hollow space likely decreases the compression slightly you can still compare the balance between the Cylinders.

Removing the Injector to do the compression test means you need a new Heat Shield when you re-install the Injector. The Heat Shields are resonable on the internet but if you buy the locally they can be like $4 each.
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  #9  
Old 03-13-2016, 11:25 AM
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The kit has a thick hollow cylinder you are supposed to install around the injector fitting to displace the volume the same as the M-B injectors. I don't know how close it matches, but I measured ~405 psig on most cylinders of the replacement engine for my 1985. The original engine measured ~250 psig and didn't like to start on cold days (later failed). Thus, I doubt it reads low and is certainly useful for diagnostics.
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  #10  
Old 03-13-2016, 02:17 PM
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Quote:
Originally Posted by OM617YOTA View Post
EUREKA!

That dang blasted 90 deg elbow in the HF diesel compression tester that breaks oh so easily can be replaced with a 1/4" JIC elbow, much more stout. I paid ten bucks at the local NAPA(highway robbery) to have it in hand now, Amazon also has them for $2.45/ea and prime eligible.

Just spreading the word. This may be widely known already, I hadn't read it on these forums, but have seen complaints that the elbow breaks too easily.
Do you have a pic or p/n of the JIC elbow? Not sure which HF kit elbow you broke. As I recall, the HF kit has elbows that thread into the glow plug hole and there is also an elbow with a quick disconnect.
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