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Old 08-08-2011, 01:05 AM   #1
Type2Teach
 
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Default Injector Leak-off Test

Do you think you have a bad injector? Here's a VERY simple test you can do to determine if you have one or more injectors that are already dead or on their way out.
In fact, it's SO simple that while you are doing regular maintenance, it might be a good idea to check the injectors before one leaves you stranded. And from what I've read on the list, it's WAY easier to get injectors out of a hot engine than a stone cold one.

[EDIT - UPDATE: I have learned that doing the test with the engine hot is a more accurate way to test the leak off quantity. http://sprinter-source.com/forum/sho...&postcount=47]

1. Purchase 3/8" ID clear tube from home depot- 2ft
2. Cut it in 4" lengths.
3. Take injector cover off
4. Pull clips off of each of the return fittings on top of the injectors
5. DON'T LOOSE THEM (I keep a clean peanut butter jar with lid around just for this purpose- they store the cut sections of tubing in them when not holding the clips)
6. Carefully pull the return line plastic fittings up and off the injectors (they can break- I've never broken one, but I have read on the forum that the only source for them is Andy)
7. Unplug the Cam sensor (next to injector #5)
8. Fit one tube over each injector head
9. Using a vice grip and cardboard, pinch the fuel return line BEHIND the "T" for #5 injector- fuel can come backwards out the fittings and you can have a mess on your hands.
10. Crank the engine for a full 10 seconds- it won't start because you have your cam sensor unplugged.
11. Check for one or more tubes that are overly full. Andy told me that 2.5ml or more fuel in the tube meant that it was time to replace the injector. I just measured this and in that 3/8" tube on the injector, that would be right at 1 and 1/2" or 37mm for the rest of the world.
Here's a picture of an obviously bad injector followed by two pictures of the same engine (mine) with the #2 injector replaced and other injectors following suit after about 500 miles.

Quote:
Originally Posted by Added by vic
Quote:
Originally Posted by doug022984 View Post
Confirmed same results seen by SneakyAnarchistVanCamper. I performed both tests. Did the one as per the manual first with the fuel rail solenoid unplugged and got ZERO leakage. Not even a drop of fuel appeared above any injectors. However, when I plugged the fuel rail solenoid back in, I got results similar to other posts in the writeup. The picture is after performing the test with solenoid plugged in. Regardless, since both tests appear to have passed (#5 was the worst, but still under 1.5"), I'm deeming my injectors OK as far as this test is concerned. I'm still hoping maybe someone has an answer why the two different methods produce different results and which one should be used for determining when to replace injectors.
Quote:
Originally Posted by abittenbinder View Post
The injector leak off test is useful when diagnosing starting issues at cranking speeds.

The fuel rail pressure needs to be above 3000 psi for starting to occur.

For the test to be valid you must have proper feed pressure and the rail solenoid needs to have its electrical connector plugged in.

Rail pressure with solenoid plug disconnected will be limited to approx. 870 psi max.

If you do not have cranking speed rail pressure issues, this unplugged reduced pressure will not be enough to reveal accurate injector leak off.

If you have serious starting issues due to very low rail pressure (and caused by severe injector leak off) the offending injector(s) will likely be revealed at low rail pressure and electrical plug status may not matter.

Doktor A
Attached Images
File Type: jpg injector test 1.jpg (60.9 KB, 2903 views)
File Type: jpg injector test 2.jpg (54.8 KB, 2674 views)
File Type: jpg injector test 3.jpg (54.7 KB, 2629 views)
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Last edited by Aqua Puttana; 08-09-2017 at 12:56 PM. Reason: Add solenoid connector info
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Old 08-08-2011, 02:26 AM   #2
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Default Re: Injector Leak-off Test

Thanks Joel! I had been searching for a concise write up of the DIY approach for this since you replied to my hot start problem post the other day.
I'd found the service manual version at this post:
http://sprinter-source.com/forum/sho...&postcount=124
Your way is more my style... I'll give it a go this week.
-Alex
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Old 08-08-2011, 03:00 AM   #3
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Default Re: Injector Leak-off Test

No problem, Alex. I was surprised that there was no DIY write up on it, and I actually just heard about it from another member when I tried it. I never saw that post you linked to.
It was just so simple and effective and I had photos, so I figured I would take a few minutes to write it up. Good luck and let us know the results of your test.
PS- if you happen to have a bad injector and need to replace it, there's a great write up on it here in the T1N Write-Ups section. I did #2 and my experience was an easy one. I didn't need the special puller. I'm replacing #5 tomorrow, and I'm hoping I won't need the puller for that one, either.
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Old 08-10-2011, 05:12 AM   #4
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Default Re: Injector Leak-off Test

Thanks for the write up and the pics. Also, you can get a hose clamp at Harbor Freight for about $4-5.
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Old 01-13-2012, 07:30 PM   #5
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Default Re: Injector Leak-off Test

thanks for this. andy told me how to do this on the phone the other day and i was a tiny bit confused. this make it all come into focus. should check it this weekend.
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Old 04-10-2012, 11:16 PM   #6
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Default Re: Injector Leak-off Test

Thank you for sharing a great write up. One question, where did you get the new injectors from and how much should I expect to pay per injector?
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Old 06-02-2012, 12:58 AM   #7
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Default Re: Injector Leak-off Test

1/2" is OK.
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Old 06-02-2012, 02:22 AM   #8
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Default Re: Injector Leak-off Test

[QUOTE=generalpatton07;184105].... the leak test and all injectors go up about 1/2" up the tube with fuel and was wondering what that meant. /QUOTE]

Much more than 1/2" of fuel in the tube means a clogged or worn or defective injector, needing replacement.
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Old 01-06-2013, 07:04 PM   #9
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Default Re: Injector Leak-off Test

What is the point of disconnecting the cam sensor? Is it just so the engine won't start? Or something else?

thanks
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Old 01-06-2013, 07:06 PM   #10
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Default Re: Injector Leak-off Test

Quote:
Originally Posted by woodgrain View Post
... Is it just so the engine won't start? ...thanks
Yes.
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