How to Clean/BackFlush CIS Fuel Injectors for a Porsche 911S! Projekt Airkult Episode 25

In this episode, I try to backflush some CIS fuel injectors from my 77 Porshce 911 to clean any deposits on the microscreens, and test the spray pattern afterwords. I've recorded the spray patterns at 240fps in order to analyze how well the cleaning worked. I also show you how to stack in the injector inserts on the intake runners.

I was following this thread:

CIS stands for Continuous Injection System, and unlike modern EFI where the injectors pulse a mist of fuel at a specific time, this system just sort of mists fuel constantly into the intake runners, so the fuel vapor builds up on top of the intake valve, and gets sucked in on the intake stroke.

My system was functioning properly, so my goal was to document the CIS system, tear it down to inspect everything, and slap it back together. I also modified the intake runners by removing some extra bosses and mounting flanges, which should clean up appearance and help shed a tiny, insignificant amount of weight (I weighed it, 5 ounces!! lol).

Links:

Initial Teardown:
Airbox Inspection:
Reassembly of CIS system:

Best Source of CIS Info on the Internet:

New Injectors:

LiquiMoly Diesel Purge:

Injector O Rings:

The BEST Engine Rebuilding Book for 911s

The BEST 911 Projects Book for 911s

The BEST source for information on 911 technical questions:

BEATS:

#porscheCIS #cisfuelinjection #cleanCISinjectors

[themessenger]

I have a 85' Ferrari Mondial QV... K jetronic system on it. Removed the original injectors and gave them to a fuel injection shop to be tested and cleaned. WOW ! they were all good and had a nice even spray and no drips. Gave the car at least 15-20% more power. Easy fix, cheap and very effective. Don't underestimate the value in a professional shop doing some things. It's worth every cent. Cheers.

[bertrandliang]

Fantastic video. Your experience helps provide us all not only great visualization but also the humility of sometimes doing things differently than we planned. Thanks again for doing these and keeping it real. Happy holidays.

[diederickzeelenberg]

Very recognizable. I went through the exact same. Watched that Mercedes mister on YT use diesel purge. Sourced that stuff, did my best but no cigar. Ended up purchasing new injectors too. Good job - you’re almost there!

[JarnoKilian]

Another well made video!
Btw, you are better off scrapping the old injectors. The issue usually isn't that they are clogged (especially coming off a running car like yours) but the wear of the internally. It causes drops in opening pressure and variation in spray pattern, changing the fueling from cylinder to cylinder. Worst case it causes cylinder scuffing from overfueling.
Any time you have easy access to replace the insulators/injectors/orings past 100k miles you are definitely better off doing so, and the Saab part number worked for me also. Staking the new insulators in the intake runners is safest/easiest on the workbench.

Looking forward to more videos, thanks for posting them!

[oscarmarcenaro]

I have a 77 as well and I’ve watched all your videos on this build/project and it’s IMHO the BEST on YouTube brother!! I will be tackling this similar route soon and you have made it super easy to understand! Well done!

[johnndname]

Great video you me some good tips on the injectors!Just make sure when buying new injector that you get the 110kw injection as this is the right fuel pressure for the cis.there are other low pressure injectors and if you get the wrong ones it could affect your fuel/air flow and the engine won't run right.

[TimeLapsesBaudet]

yep, este es el video que esperaba! Pense que no nos habiamos entendido cuando te pregunte! increible....de nuevo muchas gracias por tu trabajo!

[ChrisMeirose]

Everything's a hammer in a time of need...

[Clubracer]

I feel your pain on the injectors. Just went through the same exercise and ended up buying new ones from Pelican. Wish I saw your Saab tip before buying them :(. Keep the great content coming!

[jasonbirch]

I just came to the same/similar conclusion on the copper wire after messing with trying a zip tie with a split cut in it. I popped the pintle with a fingernail and just stuck the tip of the wire in. I don't like the idea of the loop and pulling it to the side when you jam the hose over it. It could bend the pintle. My plan is to hook them up to a fuel pump and really backflush them. Your spray pattern test is not accurate with so little pressure either.

[TCTV]

What was the point of tapping with the screw driver on the threads?

[jacksgerman]

These injectors are cheap, only about $50 a piece from a dealer. I've found after working on these for years that the now advanced age of these they just need to be replaced in most cases.

[sytran]

the syringe doesn't produce enough pressure to create a fine mist. very misleading title.