FA query

[Alan L]

If you get a fail result on a FA residual pressure test, can you have a good FA and a leaking pump check valve?
How do you distinguish between the two?
Thanks
Alan

[E Sully]

A residual pressure test does not show which component is leaking. Yes the FA can still be ok, you would need to remove it to check individually. The residual pressure test can fail due to a leaking WUR, fuel pump check valve, FA, or fuel distributor pressure regulator.

[Alan L]

Thanks Ed - that is what I was suspecting. Just that you see a failed Rest Pressure test and the first result seems to be to throw a new FA at it.
Have a mate with an SC hot start issue. Just piecing together where we go with it.
So the answer would be to remove the FA and bench test - if the result is suspicious.
Regards
Alan

[boyt911sc]

Allan,

You can test and evaluate a FA in situ. Disconnect the bottom port of your FA and test run the FP for several seconds (no more than 5 sec.). A good one will not leak from the bottom port. If it leaks fuel during the test, it failed the test. Place something to collect the fuel from the disconnected bottom port fuel line and under the FA during the test.

Or removed the FA from motor and do a pressure test on the bench. There are other known sources of residual pressure loss culprits for SC’s.

Tony

[Alan L]

Good tip Tony - thanks.
Alan

[Schulisco]

I always recommend a bench test of the FA with pressurized air!
The problem is that the FA must not only be tight for fuel, it's also urgently required to move free and smoothly! Many FA are tight for the fuel, but their plunger cannot move free and smoothly any more and gets partially stuck or hesitates the sweeping fuel pressure changes (due to wear and corrosion). This heavily affects the mixture and running culture of the engine!

How can you test it, see my postings there:
https://forums.pelicanparts.com/porsche-911-technical-forum/1119829-accumulator-pump-check-valve.html

After replacing the FA check (and adjustment if out of spec) of the mixture is mandatory!

Thomas

[avenbugt]

Originally Posted by E Sully

...Yes the FA can still be ok... a leaking WUR,....

English is NOT my first language but I think I can make myself understandable and I understand 80% of English, French and German text. I've a friend who helps me with the other 20% (Google).
My biggest problem is the abbreviations!
There are some threads with dozens of them. In this thread there are only a couple:
FA ?? WUR ??
Help me...

[Schulisco]

@avenbugt

FA = Fuel accumulator
WUR = Warm Up Regelulator

All the CIS components are briefly described here:
https://cis911primer.com/pages/comp_page.html

Basically any CIS component has it's own abbreviation, assembled from their initial letters, like the CSV = Cold Start Valve, AAR = Auxiliary Air Valve, etc.

If you're not so familiar with CIS I heavily recommend to watch the CIS related videos from Curts (KlassikATS.com) marvellous playlist about the 2.7l 911, the CIS components are pretty much the same on the 3,0l SCs except Lambda controlled US SC from 1980-83 as they add an electronic lambda control on top of the all mechanic CIS:
https://www.youtube.com/playlist?list=PLkWFofpgz2OgF9FdliKnlzuY0pygqRkMj

Also literature like the mentioned CIS primer...
Further reading:
https://www.benzworld.org/attachments/cfe06613-d83a-4461-9d69-260cb7ab4da4_bosch_k-jetronic-pdf.2840103/
https://www.benzworld.org/attachments/k-jetronic-workshop-manual-pdf.2840104/

Add: Here's a very basic introduction made by VW / Audi in their self study programme, unfortunately in German and not English:
http://www.volkspage.net/technik/ssp/ssp/SSP_44.PDF

Thomas

[avenbugt]

@
Schulisco

Thank you for the useful links!
Vielen dank.