SC Injector Cleaning - Will the Poor Man's Method Work?

[86 911]

Hi all,

I've been doing some maintenance on my car lately. One of the projects has been to replace the injector sleeves and seals on each cylinder ('78 911 SC engine) & testing the injectors.

A co-worker with an '82 SC mentioned that an easy way to test the injectors would be to remove each injector and spray carb/brake cleaner (with a nozzle extension to fit through the injector hole) inside of it in order to observe the spray pattern. If the pattern is normal, the old injector is good and will be re-used. If not - well, time for a new injector.

I have read about all sorts of intricate methods of cleaning these things using the search feature, but.... what's wrong with using this simple method? Just wanting some insight! So far, all looks well and spray patterns seem normal. The only thing I'm worried about is consistency... does the carb cleaner being sprayed through the injector actually simulate fuel being sprayed out of the injector the same way? Let me know your thoughts!

[porschetub]

Originally Posted by 86 911

Hi all,

I've been doing some maintenance on my car lately. One of the projects has been to replace the injector sleeves and seals on each cylinder ('78 911 SC engine) & testing the injectors.

A co-worker with an '82 SC mentioned that an easy way to test the injectors would be to remove each injector and spray carb/brake cleaner (with a nozzle extension to fit through the injector hole) inside of it in order to observe the spray pattern. If the pattern is normal, the old injector is good and will be re-used. If not - well, time for a new injector.

I have read about all sorts of intricate methods of cleaning these things using the search feature, but.... what's wrong with using this simple method? Just wanting some insight! So far, all looks well and spray patterns seem normal. The only thing I'm worried about is consistency... does the carb cleaner being sprayed through the injector actually simulate fuel being sprayed out of the injector the same way? Let me know your thoughts!

Mechanical injecters are best tested on a fuel bench for leakdown and spray pattern,if they show poor results they are cleaned in an ultra-sonic cleaner and retested ,that fuel shop will give you a verdict after that.
They are usually very durable if no water has gone thru the system,otherwise the pintles will leak fuel after opening.
Replacement is the norm if the test is poor
Spray pattern can be fine but leakdown tests are the kicker here.
So I don't think the DIY will really sort it if there wear or longterm damage from water/crap due to old fuel filter etc.

[Robbbyg]

This is a good read by Mr Fairman, similar to what your doing he shows cleaning and testing of the injectors.

Many say cant be done at home and some say it can, i know ill be giving mine a go at it pretty soon



Backflushing CIS injectors

[RDM]

I can't imagine how a spray can would provide enough pressure to open the injector. Experts say 36 - 52 psi is the correct opening pressure.

The spray pattern can be examined by pulling the injector, leaving it connected to its hose, and lifting the metering plate to activate fuel flow (engine off, key on, and injector in a glass jar to collect the gasoline). Once the metering plate is released, the injector should not drip.

See Help interpreting CIS Injector spray pattern for more.

[86 911]

Thanks for all the input and for the advice. This car is a daily driver, so as long as the spray pattern compares to a new injector's pattern, I'm not too concerned about the ultra specifics.

Dru - you're right - with the spray can alone, it's impossible to open up the injector. I use a can with the provided extension and it seems to do the trick just fine as seen here:

[scarceller]

In the CIS engines. I have removed each injector from the intake runners and then put each one into a small plastic bottle (you need 6 bottles). Then jumper the fuel pump so it's always running and push up the air plate in the air funnel. The injectors will spray fuel just as they do when working in car. First observe spray pattern on each. Then empty the 6 bottles and repeat this time let them spray till the bottle fills about 1/3rd. Then simply place each bottle on the bench and compare how full each bottle is. The thinner and taller the catch bottles are the easier to see the levels in the bottles. You now know how each injector compares to the others volume wise. The neat thing is you can repeat at low volume spraying and hi- volume spraying but simply lifting the funnel plate a little or a lot.

I sold my 75 911 years ago but this method was shown to me by a old school 911 fella.

[86 911]

Sal - great method- thank you for sharing!