Injector Health Question/Opinion

ncos

Member
Just ran a few tests on my injectors and I was looking to get some perspectives on whether to pre-emptively replace any injectors or not. To avoid well poisoning, I'll refrain from sharing the (trusted and experienced) mechanic's votes.

The goal is to make this vehicle as bullet-proof as reasonable/practical.

First test was a Quality correction test...see picture.
Second test was a leakoff test...see picture for most leaked-off injector.

Thanks for the crowd wisdom.
 

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kansascitysprinters

t1n everything
How crucial is the van for you? When I'm on the fence for if an injector should be changed out, I just remove them and have them tested at a diesel fuel injection, ours is called pacific fuel injection, I believe there's one in DC. If you could have the van down a few days, might not be a bad idea. They will give you exact health of each injector, and for me that brings added peace of mind.

My understanding on that smooth running test is if it's over .5 it's over compensating, and should be replaced.
 

ncos

Member
How crucial is the van for you?

My understanding on that smooth running test is if it's over .5 it's over compensating, and should be replaced.
We’ve invested a lot, so it be pretty crushing to lose an engine due to an injector issue. Regarding the test: Your understand is consistent with the mechanic. Also, in a separate post, Dr A cites +\- 0.5 mm3/stroke as the criteria. That makes me also wonder about the two negative values that exceed .5. I’ll note that all of those criteria are inconsistent with the .005cc value criteria on the diagnostic screen shot, but that could be a unit conversion error by the software cloner.

I’ll ask about the testing possibilities.
 

Cheyenne

UK 2004 T1N 313CDi
We’ve invested a lot, so it be pretty crushing to lose an engine due to an injector issue. Regarding the test: Your understand is consistent with the mechanic. Also, in a separate post, Dr A cites +\- 0.5 mm3/stroke as the criteria. That makes me also wonder about the two negative values that exceed .5. I’ll note that all of those criteria are inconsistent with the .005cc value criteria on the diagnostic screen shot, but that could be a unit conversion error by the software cloner.

I’ll ask about the testing possibilities.
0.005 cubic centimetre equals 5 cubic millimetre so on that basis all your injectors pass the on-screen requirement.

My view is that if you are in any doubt then get them tested professionally.

Keith.
 

ncos

Member
Also, in a separate post, Dr A cites +\- 0.5 mm3/stroke as the criteria. That makes me also wonder about the two negative values that exceed .5. I’ll note that all of those criteria are inconsistent with the .005cc value criteria on the diagnostic screen shot, but that could be a unit conversion error by the software cloner.
Ok. So I think I have got all this cleared up. And I think the results of this test are completely fine. Here's my supporting evidence:

1. The diagnostic screen gives a criteria of +0.005 cc/stroke as the replacement threshold. Converting to the units of the test result (cubic mm/Hub) and translating the German word "Hub" to the english word "stroke", gives you test results that range from -0.0006 to + 0.0008 cc/stroke. If you believe the diagnostic software didn't mess up the units, the test results pass (as pointed out by Cheyanne).

2. I quote Dr. A above, but found later corrections from him:

Jan 8th, 2008, Dr. A cites the criteria as +/- 0.005 cubic mm/stroke.
I was a bit too generous with that pass/fail threshold-my memory did fail me. The tolerance is +/- 0.005 cubic mm/stroke.
By this criteria the results fail on all cylinders by a factor of a 100 or so. Yikes.

April 3, 2010, Dr. A, after lots of unit conversion confusion back and forth, sets the record straight.
Lets start over here. The injector correction threshold should read +/- 0.005cc/cyl, not cubic mm/cyl.

That makes the DAD metric displayed threshold +/- 5.0 cubic mm/cyl. Any correction value greater than this indicates a possible issue with either the injector or engine cylinder or both.

Doktor A
Yay! A clean pass.

3. As a reality check, I used this screen shot: https://sprinter-source.com/forum/attachment.php?attachmentid=22393&d=1270232634 and did some math to see if the units make sense. It specifies correction values on the order-ish of mine in the same units, and cites total injection per cylinder in those same units. Using the idle RPM and those values you'd arrive at a fuel consumption of about .26 gal/hr at idle. This number ballparks well against other idle fuel consumption rates found on this forum. This really just provides some idea that thresholds on the order of .005 cc/stroke make sense whereas 0.005 cubic mm/stroke do not.

Additional Note: I talked to Dr. A this morning (before finding a lot of this). His perspective was the test can be misleading (ie, affected by non-injector stuff) and I should be more concerned with having a properly seated OEM air filter from an engine killing perspective.

Bottom Line: The threshold for this test is +/- 0.005 cc/stroke. Less than that is acceptable. Mind your units as you convert from the reported values to the units of the threshold.
 
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kansascitysprinters

t1n everything
Hmm. Gonna need to reread that. Thx.

For what it's worth I've also had a set of injectors that have tested within what I've understood correct specs to be, and after removal and testing at Pacific fuel injection, all 5 failed.

I'm really of the opinion that if someone owns a van with 200k, and they plan to keep it long term, it's a good idea to have injectors removed and tested, especially if they're unsure to prior owners fuel filter regiments.

Personally I've seen bad injectors kill multiple engines last year. I've actually got a van in the back yard right now with a blown engine from failed injectors.

Just my .2c
 

Eric Experience

Well-known member
Ncos
The injectors normally last the life of the engine if the fuel is clean. The MB fuel filter is the key to this, the MB filter is good for 3 microns, most other filters are 6 microns or more. The MB filter may cost a bit more but is a lot cheaper than a set of injectors. or a cracked piston. Eric.
 

220629

Well-known member
Thanks for the research and posting the details. :thumbup:

Just ran a few tests on my injectors and I was looking to get some perspectives on whether to pre-emptively replace any injectors or not. To avoid well poisoning, I'll refrain from sharing the (trusted and experienced) mechanic's votes.
...
Do you think that the mechanic was interpreting the data correctly?

:cheers: vic
 

ncos

Member
I do. But the goofy change in units and knowing it was a clone had me paranoid...and until I had waded through all the forum content on the test I was flip-flopping back and forth.

In keeping with that paranoia, it sounds like I should get all of them tested anyways in the not to distant future given the mileage and uncertain history.
 
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