Backflushing CIS injectors
 

It's been posted before and here's a few pics I snapped today while backflushing my injectors. I'm redoing the top end of my motor so my injectors have been soaking in techron for around two weeks now.

I clamped an injector pintle end up into a bench vice.
Then took some copper wire and seperated the fine strands and cut 6 of them about 2 or 3 inches long.

Make a tight little v in the middle of the wire and loop it around to an oval O just big enough to stick the end of a hemostat through.

Then very carefully and as light as possible clamp the hemostat on to the injector pintle and lift it up just enough to get the edge of the wire under the pintle and hold it there lighty.
Then loop the wire around the pintle shaft and fold it over the sides of the injector so it holds the pintle open a little.

Take a piece of 8mm fuel line (i used some 8mm brake resovoir line from an old BMW I had) and push it over the end of the injector and hose clamp it.

Now spray some brake clean into the hose filling it up. Then take an air blow gun and push it into the other end of the hose and blast it with 120psi of air pressure from an air compressor.
Any crud that may be on the screen inside the injector will be blown out. Soaking the injector in techron for 2 weeks should help make anything on the screen loosen up first so it gets blown out.

Then loosen the hose clamp and carefully remove the hose without pulling the wires and possibly stretching the pintle spring inside the injector as you work it off.

Test the injector by sticking the plastic straw on a can of brake clean or carb cleaner into the other end of the injector and spray it. The plastic straw fits inside the injector and seals pretty well and the pressure in the can opens the injector and the solvent sprays out the end like gas when the motor is running. You can see if the spray pattern is a nice even cone shape.
In a week or so I hope to have the motor back together with new pistons and cylinders and be on the road again.

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Another great write up. Thanks Jim.

The springs get weak on old injectors. You wouldn't be able to generate enough pressure with a warm brake cleaner can to open a new injector. I'd bet backflush cleaning is about 60% effective anyway.
Does it make sense to thrift injectors in a multi-thousand dollar rebuild? I wouldn't do it.
Just something to keep in mind.

mine dont have a lot of miles on them and i can open them with a can of carb cleaner

When I worked on brand new grey market Mercedes Benz 500SEL's, SEC's, and SL's adding on aftermarket lambda systems and catalytic converters in the early eighties so they could and would pass emsissions and be registered in the USA I took brand new CIS injectors from brand new Mercedes 500 series cars and stuck the straw from a can of carb cleaner in them and sprayed it. Guess what... the injector opened from the can pressure and sprayed exactly like my 930 injectors do.
So maybe you are wrong or just never tried it.

Also, I did this procedure on these same 1987 injectors from my car around 6 years ago the last time I had them out. The car ran perfectly and had a pefect smooth idle afterwards so again I think your wrong.

Another thing I just thought of... I'm basically at sea level a mile west of the Atlantic Ocean in South Florida so the differential pressure between whats in an aerosol can of brake clean or carb cleaner and atmospheric pressure is as high as possible... :)

I've done it more than once and always with the same result.
Maybe you should try it.

I posted a picture of me doing it... you need glasses or open your mind :)

Nice write up Jim.
I've cleaned a lot of these and find if they are not too old/rusty the fix will work for a time and perform acceptably but never as good as new.
The cost of new is prohibitive, however it is a one shot deal as they will last a decade or so. For me the real issue is the difficulty of R&R and the risk of leaks. If the lines are over tightened just once they are ruined. The left bank is fairly hidden so hard to detect a leaker until fuel runs down between the heads onto the heat exchanger. Just something to watch out for.

another great write up Jim and again as usual - appreciate your time and insight

this is very much on my springtime to-do list... not ideal remedy or not, it's better than doing NOTHING - in my case, at least

will make for good piece of mine if nothing more

I did the same thing a year ago. Also did the harbor freight ultrasonic cleaning.

Helped a little bit, 2 of the injectors still didn't have a good pattern.

I did the same thing Jim did, and backflushed with a pint injector cleaner. Brake cleaner easily shot through the injectors, including the new ones.

There is no guarantee this will work, though given the price of new injectors, worth trying!

Bo

Good write up Jim. I posted this on another thread about the insides of an injector. The parts are easily replaced IF one could get inside without ruining the injector body. The filter screen snaps on top of the schrader valve. The spring inside the schrader valve is held in place by a small clip. You can see how back flushing might clean up that double sided screen. So it does make sense to back flush.

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Thanks for posting Jim. I'm gonna give this a try. I usually just soak in Techron and blow carb cleaner through them to check pattern. But you made this look easy! Ignore the trolls...

That's Pretty much the method I used. Had purchased 2 good condition injectors from fellow Pelican and used the best of the 8. After soaking and cleaning I did a flow test WITH the CIS system into plastic soda bottles and matched the best and most accurate flows. Highest flows go to cylinders 2 and 5. Or so I've read. You can also get different flows from different fuel lines (think of it as an afternoon science project). It's definitely worth the time and effort. Still wish injectors weren't so much $$$ but what r ya going to do?

Boy, this is going to come off rude, but it's pent up in me for awhile.....

I read posts like these and I feel like I'm not part of the brand. This mentality of throwing away parts for peace of mind is something I'll never understand.

It's mechanical made of metal parts, not plastic with engineered wear parts making them disposable.

Why the hell would you throw them away? Too many checkbook mechanics, not real mechanics like Mr. Fairman here......

Good job JF.

:) :)

Good post Jf,
I checked the spray pattern on mine they werent round like yours they were sort of intermittent crescent shaped, at first i thought they were made this way because most of mine were only squirting out one side

I didnt soak mine (should have) i dipped mine in injector cleaner and filled them up with the liquid, i then got a Butane lighter gas refill can and stuck it in the end and pushed down, it worked to a point ie from little spray to a nice steady half moon crescent shaped spray, which was steady,

But do all years models need a whole circle spray pattern..?
or are some different in the spray heads?

If they all need a complete round spray,, ill have to take mine out again :(

Hi Rob, unfortunately for you, all of the years have the same round/cone spray pattern . . . sounds like yours are still quite plugged up (the crescent pattern you describe).

The pintle is supposed to move in a high frequency buzzing pattern, and thats what atomizes the fuel into a cone. If it doesnt make a cone, the injector is bad.

Bo

No, I'm referring to trying to open new injectors with a can of carb cleaner.
I have tried to backflush old injectors but the risk/reward wasn't there for me. When I'm at WOT I don't want any nagging thoughts of a burned piston creeping into my consciousnesses :D but to each his own.......The biggest advances in engine emissions and performance have occured due to improvements in fuel delivery and atomization. From carburetors to EFI to direct inject, fuel atomization is the thing that delivers power and economy. Since most of us are running at enhanced boost levels the margin for error in proper fuelling is smaller than a stock configuration. I see new injectors as cheap insurance vs any engine damage that could occur.
Tippy, since you think I'm a checkbook mechanic, your welcome to come to Detroit this weekend and assist me with the installation of my engine/transmission.

it would not hurt just as a routine maint to pull them and clean them every 30k miles. that might ease your conscience at WOT.

JFairman,

Thank you for posting this procedure. While I went ahead and ordered new injectors for my current round of maintenance I do plan to clean my clean my existing injectors and keep as spares or offer them to those that may need spares/replacements for their own cars.

Keep up the good work. You're a great asset to the 930 community!

Pretty sure no one here would offer too much assistance to you right now. A guy tries to post some helpful info and you dog him for it. That's not what this forum is about.

I didn't see any dogging going on - one guy has an idea on cleaning injectors and another thinks it doesn't work - a simple differing of opinions based on the personal experiences of both members. I would call a discussion like that very useful to any tech forum.

And no offence to Jim, but even an experienced injector shop like Witch Hunter Performance, says that CIS injectors are non-serviceable and should be replaced if not flowing properly. http://www.witchhunter.com/injectotype1.php

"Serviceable" is a reative term with varying degrees of difficulty and completeness associated. For the average enthusiasts these fuel injectors are not serviceable. For someone with Jim's skills, they are. If serviceable implies rebuildable, they are not.
The most important aspect is to properly test them when complete and to test periodically going forward. They may function within specs for a time, but typically not as new and not for as long. It is a tool that should give improvement and buy some time before plunking down several hundred bucks for a new set.

"Serviceable" was my term, not one used on the WH write-up on CIS injectors. Specifically they say that the CIS injectors do not clean well since they have non-removable filters, can not be back flushed, and should be replaced if not performing well. I know they used to clean CIS injectors, but stopped some time back, presumably due to poor results. It would be interesting to find out if they did the "hold the pintels open" bit that Jim demonstrated and/or what they mean by "can't be back flushed" since obviously, Jim and others have indeed back flushed them.

Brian, if the injectors are serviceable, can you direct me to a factory procedure for backflushing injectors?

This has been an interesting read, and I would concur with Ronnie's comment:
"I didn't see any dogging going on - one guy has an idea on cleaning injectors and another thinks it doesn't work - a simple differing of opinions based on the personal experiences of both members. I would call a discussion like that very useful to any tech forum."
I did the backflush thing as Jim described several years ago with pretty good success but for one injector that just wouldn't spray quite right. Pretty simple, pretty effective overall even if it doesn't bring the spray pattern completely back to new.

Just thinking out loud now; I wonder if a person could hook up a vacuum pump to the pintle end and in so doing pull sufficient vacuum to open up the pintle....then suck the cleaner of your choice through the injector? And I wonder if it wouldn't be worth the effort to disassemble the injectors (IF that can be done) and remove that damn screen all together (the thought being that modern fuel filters should remove any contaminants before the fuel ever gets to the injectors)?

Good write up!

Just to mess with you...

Let us say there is 3bar of pressure in the aerosol can. At sea level there is close to 1bar of atmospheric pressure. The guy doing the same thing with the same 3bar pressure can in Leadville in the Rockies sitting at about 11,000 feet above sea level. Considering the atmospheric pressure is half of sea level pressure at 18,000 feet (0.5bar) we can make a SWAG and say the pressure at 11,000 feet is close to 6.33bar. The conclusion of this would be that the guy at Leadville has got a delta pressure of about 2.4 whereas you have a pressure delta of only 2.0 bar.
In other words. he is better off regarding pressure delta than you in Florida.

The factory has no interest in servicing injectors for many reasons. This is strictly an enthusiasts endeavor.

I bought 6 new and have never regretted the engine runs like a dream :)

Would an ultrasonic cleaner do anything for these injectors? I admit to having no real knowledge of how such cleaners work. John

I tried the ultrasonic deal and didn't notice any difference. Could have been the fact that it was a cheapie ultrasonic cleaner my wife bought to clean her jewelry. Shh... Don't tell her.

Hit the wrong frequency and there will be no injectors in the ultrasonic cleaner.

That's a good question though!

I also did the same thing a few years ago, to a tee. I also used my air compressor and blasted techron through the way they normally operate to see the circle pattern.
I can get Brian's point about not bothering to do it anymore due to mixed results. If you're selling something, the end user doesn't want mixed results. If you're doing it in your garage, and you get a bunch of crap out of them like I did, you feel better about it. But the results may or may not be worth paying for. I wouldn't want to go through it all, making what's probably a pretty small margin, and then have to back them up with my reputation. With 100k on what I'm sure are the originals, I'm glad I did it.

Could one of those reasons be that they consider injectors to be subject to wear, especially since many of the cars that use them are getting rather elderly?

I think Back flushing shouldn't be done due to the design of the filters inside
i believe you should flush in the same direction until they're clean
If they don't come good that way then replace

It's standard procedure to backflush filters. Going in the direction of flow only lodges the debris in.

Darn now for the FIFTH time this month ive got to take mine out again :rolleyes:

I cleaned two sets of euro 930 injectors, wired the pintles open, soaked them in concentrated Techron for a week or two.

Then I ran them for two weeks in a relatively high-power hobby ultrasonic cleaner with a heated tank ($70 from Amazon), and a teaspoon of dish soap as surfectant. (Without surfectant, the cavitation doesn't work, heat makes a big difference to effectiveness too)

I'd remove them every day or so, change the solution (usually when it got so dark I couldn't see what was going on anymore, or when cavitation bubbles stopped forming in the solution), backflush with brake cleaner and put them back in.

Took them to my wrench, told them to discard any they wouldn't put in their own motor.

They have a Bosch CIS tester on the bench. They said the crack pressures were all fine - but they discarded two for bad spray pattern.

The injectors were amazingly clean. Eventually. It's not that fast a process - an industrial cleaner would probably work much better.

But even so, stains that looked like rust turned out to be decades-old baked-on fuel varnish or something - and lifted off. Slowly. You could sometimes see little black particles drifting out of the pintle or the thread. The solution ended up filthy quite quickly at first, then slowed down after the first week, then it seemed to be diminishing returns - I gave up after I didn't really see much different for 3-4 days, which was about two weeks of just running it all the time.

I'd say it can't hurt.

There's scientific data that needs to be applied in ultrasonic. More transducers equals more power. Too much, and it'll blow the injectors into bits if you reach the right frequency and amplitude.

Worked with this a little in aviation and it was a serious topic due to the ability to destroy or weaken parts.

I suspect the household ultrasonic units you guys used were simply too weak to work effective.