Cleaning CIS Fuel Injectors

[fireant911]

In the recent past I have seen a few posts about owners pulling their fuel injectors for either testing and/or replacement. This evening as I was driving home I had a thought concerning the cleaning process that I would like for some seasoned Porsche veterans to carefully take into consideration. Is it possible to clean the injectors really well without ever removing them from their home?

Many of us use Techron or Berryman’s B-12 Chemtool diluted in our fuel systems that helps in removing any buildup from the injectors. In reading the Bentley Porsche 911SC Service Manual, it is recommended to use Shell Mineral Spirit 135 or equivalent when testing and cleaning injectors though with this procedure the injectors must be removed from their existing location.

Would is be feasible to, for example, remove and drain the fuel filter and refill this filter with a concentrated cleaning agent such as the Berryman product in its purchased form. Reattach the fuel lines to the filter, remove the spark plugs (to prevent any sort of hydraulic lock), activate the fuel pump, and raise the air sensor plate for a couple of seconds to spray the cleaner. Repeat the raising of the air sensor plate (after reactivating the fuel pump) again for a couple of seconds on subsequent days until the supply of fuel injector cleaner has been exhausted. At this point crack the engine over to remove any residue Berryman product from the runners and combustion chamber, reinstall the spark plugs, and start the engine. I am currently under the belief that this repeated, concentrated dosage of cleaner would have a higher likelihood of correcting any irregularities with the spray pattern (providing that the injector is still salvageable). What are your thoughts with this fuel injector cleaning proposal?

[concentric]

It cost me $30 bucks to have mine professionally cleaned when I had my first motor put together at a local P-car shop with a special machine to do this. For me, trying to mess with them wasn't worth it.

I believe it cleans using ultrasound, which might be more effective for removing particulates that aren't dissolvable by cleaners.

JCM

[sammyg2]

IIRC CIS injectors have a very fine mesh screen in them. If that's the case it would be very hard to clean that screen if it was clogged with particulates. Other than that your plan sounds feasable, but not sure if it's economical.

[rdane]

Just a thought but no new ejectors in the N/A CIS engines younger than 20 years old. Machining tolerences and production techniques have improved some in the last 20 yeras.

You might want to just buy new ones. They run around $40/$45 each depending on where you buy them I was surprised how much of an improvement can be had by the exchange.

[Jubbie]

I have heard that you can take the injectors out and spray chemtool carb cleaner through them. The red straw sprayer just fits in the inlet and there is enough sealing around the straw to put enough pressure to open the injector. If it has a good spray pattern, then all is well.

Has anybody used this technique?

[Andras Nagy]

When I did my rebuild, I filled the injectors with carb cleaner and then blew them out, carb cleaner and all, with comporessed air at 80 psi.

There was enough carb cleaner inside the injector (from where the fuel lines attach to the tip of the "pittle"), and one can actually see the spray pattern against a dark background, such as grass. If the spray is not conical on the first blow-out, then I just repeated until it was, usually within two or three such "purges".

The car purrs now, probably as a result of nicely atomized spray.

[CARRERIC]

Marren Fuel Injection www.injector.com Sells a matched package of new injectors fo about $200. Well worth it.

[IROC]

I didn't realize that CIS fuel injectors have gone up that much. I replaced mine (on the old 2.7) a few years ago and they were $24 each.

I've heard mixed reviews on the success of cleaning fuel injectors. IMHO, CIS injectors are cheap enough that you should strongly consider replacing them vs trying to get them cleaned.

Mike

[Andras Nagy]

Carb cleaner cost $4.79, compressed air costs nothing.

Why spend over $200 when your injectors might be just clogged, and cost only $5 to unclog?

[Tim Hancock]

I am with you in spirit Andras, I tried some home brewed cleaning methods on my old 924 injectors that included various solvents and compressed air including a 4 hose spyder arrangement to blow solvent thru all four at once. I also made an "ultrasonic cleaner" out of an old 1/4 sht electric sander with a coffee can solvent reservoir attached to it. I never did get perfect cone spray patterns or perfectly matched opening pressures. I ended up buying four new injectors for $50 each. Later I found that I had a faulty fuel pump that would pass the flow test yet not make pressure (stupid me).

My old injectors were not the problem after all, but I did learn that I am not capable of performing injector refurbishing to new standards at home. I called all around my area and no one that I could find cleaned individual injectors. The only places around here that cleaned injectors, used a system that hooks up to newer fuel rail systems, not individual injectors. I guess it just depends on where you live.