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Checking Fuel injectors

Is there any way to check fuel injectors without taking them out and sending them away?

Thanks
Harry
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Old 07-04-2009, 09:45 AM
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The Bentley manual has a number of checks for the fuel injectors using a volt-ohm meter.

You can try sticking the injector in a glass jar to see the spray pattern, but it's kind of cumbersome keeping it attached to the fuel rail and trying to avoid fuel spraying everywhere.

They are long overdue for cleaning and restoration anyway. I sent mine to Witchhunter Performance http://www.witchhunter.com/ and they did a great job and they replaced all those parts you see. You also get a report on the condition of each.

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Old 07-04-2009, 10:32 AM
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Witchhunter no longer cleans CIS injectors. In fact, I couldn't find any business that will clean them. You will have to test them yourself but it's easy.
Take the injectors out of the intake. Take a can of brake cleaner and heat it up in hot water. Spray the brake cleaner into the injector using the straw that comes with the can. You are looking for a 360 degree conical pattern and will be able to see what you have. Also, an injector with a good pattern will "sing". Bad injectors will have to be replaced.
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Old 07-05-2009, 06:03 AM
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Isn't there also a flow test for CIS? You pull the injectors and place them in a jar, check the flow rates and the spray pattern?
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Old 07-05-2009, 06:19 AM
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Anybody know how to clean and check MFI injectors.....or who performs this service?

Regards,

al
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Old 07-05-2009, 07:57 AM
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Quote:
Originally Posted by al lkosmal View Post
Anybody know how to clean and check MFI injectors.....or who performs this service?l
Al - I've checked mine by spraying into a jar, and finding the one that was bad.

For cleaning - very close to you in Bothell:

http://www.witchhunter.com/
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Old 07-05-2009, 09:55 AM
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Quote:
Originally Posted by LakeCleElum View Post
Al - I've checked mine by spraying into a jar, and finding the one that was bad.

For cleaning - very close to you in Bothell:

http://www.witchhunter.com/
How did you do this?
Old 07-05-2009, 11:38 AM
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Pull all the injectors.

Place each injector in a jar.

Ignition on.

Push the air sensor plate up to spray fuel.

Look at the shape of the spray from each injector.

Use a graduated cylinder to measure the flow from each injector, they should be within 10%.

Clean or replace as necessary.

http://www.peachparts.com/shopforum/showthread.php?t=69652

NO SMOKING.
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Old 07-05-2009, 12:20 PM
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Quote:
Originally Posted by htbetz View Post
Is there any way to check fuel injectors without taking them out and sending them away?

Thanks
Harry
No.


Most good diesel repair shops know how to test and clean MFI injectors.
Old 07-05-2009, 04:24 PM
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Just came across this thread, and figured I would check my injectors... I tried the brake cleaner trick, and the injectors spray well when the can is fully depressed. If I depress the brake cleaner nozzle less than fully defected, the spray pattern is less symmetrical...

Does the CIS system only spray at a certain steady PSI? I assume this is so. Or, does the PSI vary depending on the motor rpm, etc?

Seems to me, I could get a full can of brake cleaner through an injector in about 20 seconds. At this rate you wouldn't get very far on a tank of gas .

Is there a certain PSI you should check your injectors at? I have the bently manual at home, but haven't had a chance to look yet. Anyone know off the top of their head?

Bo
Old 03-04-2010, 03:37 PM
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I believe there are two tests for a CIS injector. Spray pattern and 'cracking pressure'. That is the pressure the spring loaded valve opens in the injector. You want all them to open at the same pressure.

I a surprised you can get brake cleaner to open them.

The reason for the cracking pressure function is to keep the fuel from leaking down when the motor is turned off so the injector lines remain filled with gas.
Old 03-04-2010, 04:56 PM
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CIS injector - The spray pattern should be 35 cone, with an opening pressure of about 3.6 bar

Last edited by jcge; 03-04-2010 at 06:49 PM.. Reason: CIS
Old 03-04-2010, 06:48 PM
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Quote:
Originally Posted by 911st View Post
I believe there are two tests for a CIS injector. Spray pattern and 'cracking pressure'. That is the pressure the spring loaded valve opens in the injector. You want all them to open at the same pressure.

I a surprised you can get brake cleaner to open them.

The reason for the cracking pressure function is to keep the fuel from leaking down when the motor is turned off so the injector lines remain filled with gas.
Good info and accurate, as well!!

CIS injectors have a small screen inside them that not only gets clogged with dirt, but its prone to corrosion and that can also obstruct the injector and affect its pattern.

Bosch made a special test fixture to test and clean CIS injectors but its now rare they can be rehabilitated well enough to restore proper function after all this time. Now, we simply replace them in the majority of cases since they never clean up well enough to make the engine run well. I strongly recommend the frequent using a product such as Techron, LubroMoly, etc. to proactively keep these clean and functional.

EFI and MFI injectors can however, be cleaned and tested. The former ones are cleaned and tested for flow, impedance and current draw. The latter ones can be serviced by a Bosch diesel service center.
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Old 03-04-2010, 06:51 PM
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This how I clean my CIS injectors...........

Quote:
Originally Posted by htbetz View Post
Is there any way to check fuel injectors without taking them out and sending them away?

Thanks
Harry

Harry,

This is how I clean and inspect the spray pattern of CIS injectors using one (1) gallon solution of gasoline and injector cleaner. This set-up could also check for leaky injector.



Then followed by air injection. Try to use filtered and dry compressed air. Last and final step for another rinse with the cleaning solution.



I got a home-made gizmo that can clean a single injector at 75 psi with cleaning solution (gasoline + commercial injector cleaner) and inject 100 psi of compressed air if needed by turning a multi-directional flow valve. Most of the clogged injectors could be recovered and saved. But the leaky ones go to the dumpster.

Tony
Old 03-04-2010, 08:14 PM
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Quote:
Originally Posted by Porsche_monkey View Post
Pull all the injectors.

Place each injector in a jar.

Ignition on.

Push the air sensor plate up to spray fuel.

Look at the shape of the spray from each injector.

Use a graduated cylinder to measure the flow from each injector, they should be within 10%.

Clean or replace as necessary.

CIS injector test/clean, home brew... - PeachParts Mercedes ShopForum

NO SMOKING.

+1

we have a small postal scale. i poured each into a common container and weighed it, but there was really no need, the one that was bad was obvious. ialso did the lines without the injectors, i had a bad line.
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Old 03-05-2010, 02:55 AM
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I've had very good luck through the years cleaning CIS injectors with a lab quality ultrasonic cleaner.

Regards,

Jerry
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Old 03-05-2010, 04:42 AM
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Ultra sonic CIS injector cleaner

What do you use as a solution to clean the CIS injectors in an ultra sonic cleaner? Thanks,
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Old 03-08-2010, 01:13 PM
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Thought I would revive this thread... took my injectors out of a well running 930...

Shooting carb cleaner through, with the nozzle fully depressed, 4 injectors put out a nice cone. 2 did about a 3/4 cone...

Back flushed with pressurized air, with car cleaner in the line... really didn't get anything out...

Here is the thing, at lower pressures, 50-60 psi, the injector spray isn't that pretty, and some of them look like 3-4 jets shooting out. The higher the pressure, the nicer the cone... The injectors "sing" at 70-90 psi with pressurized air, can't say I heard it with brake cleaner shooting through them...

One injector doesn't spray in a cone no matter what I do (did the Harbor freight ultrasonic cleaner, etc)...

Here is my question:

With electronic injectors, they only spray at one pressure, then pulse off. With CIS the output of fuel is based on the pressure of the fuel at the injector. Well, at low pressures, these older injectors don't shoot so hot, but at higher pressures, they do.

When we home mechanics are testing them, we only test at higher pressures (brake cleaner I suspect is it 70-90psi? Do places like Witchhunter check at lower psi's too?

Seems like at idle, the spray patterns aren't optimal. Are the injectors still ok?

Anyone know of a source of good used injectors? $110 a pop just isn't in the plans right now, since the car runs well. Folks on Ferrari-chat did find the Bosch injectors without the turbo threaded shaft, for $25 or so (308's use them too). Unfortunately, the ones for the turbo are hard to find...

Any help appreciated...
Old 04-05-2010, 12:35 PM
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CIS is "suppose" to be a constant pressure to the injectors, the volume is what changes. the chambers and the metal diaphragm in the fuel distributor does all this.
the electronic injectors should also see about the same pressure, except the duration that the injector is open determines the amount of fuel delivered.

i would expect most injector shops will give you data for each injector as far as opening pressure, volume and pattern.
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Old 04-06-2010, 09:41 AM
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But to change the "volume" of the spray, you have to change the "pressure", I don't understand any other way to do it...


The CIS system doesn't "pulse" right? So, if I understand this correctly, the injectors open about 50 psi or so. At idle, you get 55psi or so, and its a faint mist. At full throttle, 90 psi? Huge spray pattern...

Correct?
Old 04-06-2010, 09:47 AM
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