rebuilding a fuel distributor

[elanko]

Hey all,
Lots of information and encouragement, but same question: Does anyone have an exploded view of the fuel distributor? Im willing to try to repair (mostly clean and re-seal everything) but without a tech. drawing, it seems like driving accross the country without a map.

[steand]

Hmmmm.....

I tried to rebuild The FD on my 924 a few years ago, but gave it up. It newer worked good.

But for you interested i took some pictures in the process, and did a writeup, thats on my old homepage.

I guess you could be lucky and rebuild it if you got the right part's and tools.

Link to My article on Fuel distributor Rebuild

[CARRERIC]

Been here and done it!! First let me say "RUST IS THE ROOT OF ALL EVIL" for CIS, it contaminates the WHOLE system. Ask me how I know??

If you have a rusting tank you must have it PROPERLY repaired. Send your gas tank to Tank Renu they open and refurbish like knew for about $400. You can not just clean a rusting tank. I sent my FD to fuel Injection Corporation and for around $250 they did a good job. Unfortunately I placed it back on the car before I refurbished my tank. I eneded up buying a new leftover FD from a fellow pelicanite and have been very pleased ever since. However since the rust conatmination I have replaced injectors, WUR, Fuel accumulator, etc. etc. etc...

Can a person rebuild a FD - maybe. I do not recommend it. Fuel leaks are way to dangerous.

My .02 cents

[robs]

Elliot,

you can measure the flow rate if you pull all 6 injectors from the intake
runners and let them spray into small cups. Lift the airflow meter plate,
let the injectors spray some time, and compare the amount of fuel of each
injector with a measuring glass. Repeat at different positions of the airflow
meter plate from idle to full throttle.

I disassembled my 1980 SC fuel distributor because one injector delivered
less fuel than the others. I found that one slit was clogged.
After assembly, one injector always delivered "full throttle" fuel amount.
I split it again and found that one O-ring had moved when pressing the two
halves together. Lube the O-rings with motor oil. After the second assembly, it
leaked. I split it again and sealed the mating surfaces with a very thin
layer of Curil K2. With this sealer, it is easy to split the FD again :-)

You need a TX27 driver for the screws. Turn the FD upside down before you
try to pull the two halves apart. Be very careful not to mix up the inner
parts. Between the two halves is a thin metal sheet. Do not twist the halves
when you try to pull them apart, because the differential pressure valves
would scratch the metal sheet. To increase pulling force, I bolted the upper
half of the FD to a large plate (with the screws of the FD). Then I turned it
upside down, stood on the plate and slowly pulled up the lower half.

I attach what Rob e-mailed me some time ago. Hope this helps!

Quote:

Have you measured the amount of fuel that comes out of each
fuel injector? Have you tried swapping fuel injectors around so
you know that it's not a clogged injector? I would want to be
certain that your #6 port really is putting out less before
disassembling the fuel distributor.

If so, then you can disassemble and clean the F.D., but it is
a tedious procedure. I think the reason John Walker only did
it once, is probably because it's not worth his time to do it
again.

I put the F.D. in a vise upside down, and used the proper
sized Torx socket to remove the six bolts. Don't remove the
six bolts up top, as they appear to be test ports? They don't
need to be removed to split the F.D.

I tapped the case halves with a wooded hammer to split them.
Pull them apart slowly so you can see how the spring loaded
parts inside go together. They will go flying if you pull the halves
apart too fast.

Now the large metal diaphragm will be stuck to one of the halves.
There is nothing really to clean on the lower half of the F.D. Just
large chambers without any small orifices. The upper half has the
areas you'll want to clean. I was only able to remove the diaphragm
by reassembling the two halves with Shellac, without the center
barrel, then splitting the halves again. That loosened the diaphragm.
If it's stuck to the lower F.D. half, don't worry about it. Nothing down
there to clog.

After removing the large nut in the center of the bottom half,
the center plunger barrel pushes up from the bottom. Do take
note of it's location relative to the case half. Mark it somehow
if you can. There is a hole in the side at the bottom of this barrel,
and I'm not sure where it should be in relation to a hole in the
bottom of the lower case half. I did not know about this hole when
I took mine apart, and it took a few tries to get it aligned so it would
work again. I'd like it if you could let me know how those holes are
aligned to each other.

Actually, you may not need to remove that center barrel. Just
make sure that the six tiny slits are clear. Nothing below the
barrel would cause a reduction of fuel to only one injector.

Mine was spotless inside, so I didn't have anything to clean. I
replaced the six small orings that loop around the slits on the
barrel, as mine were dry rotted. I just used #6 orings from the
hardware store, and lubed them with oil.

I first reinstalled the center barrel with it's hole aligned with the
hole in the lower case half. Once in the car, it ran all the injectors
at full blast, and filled my crankcase full of fuel. Yuck. I had to
pull it apart, and put the holes opposite each other, and then
it worked fine.

I applied some automotive Shellac to the case halves to seal them.
It leaked when I put it together without any sealant, so you need
some. I've also heard that Locktite 574 works as well. When
reassembling be very watchful of those six orings. Don't seal it
together without being certain those orings are in place. Mine went
together the first time with one of those orings bent over, and I didn't
notice. Once back in the car, the F.D. sprayed fuel all over the place.
Had to do it over.

I had to reassemble, install in the car, then disassemble this thing
three times before I got it right. Once because one of the small six
orings got bent over, again because the center barrel was in wrong
with relation to that lower hole in the case. And once again when I
put it together without any sealant. Hopefully you can do it in one try.

[Superman]

I'm another person who does not believe these can be rebuilt. They are simple items, but with ridiculously tight tolerances. The plunger is matched to the bore so closely that fuel, under 60 psi, does not leak out, but the plunger is loose enough to travel easily up and down the bore. Gentlemen, this is what machinists call a "honeymoon fit." There is no o-ring. When that plunger gets scored, the FD is scrap metal. I have yet to hear an explanation of FD rebuilding that makes me think it's a service worth more than $5. As far as I am concerned, you can clean them, and that's about it.

[Brent 930]

Measuring the flow rate by draining fuel in a cup is crude at best even though it will tell you if one isn't flowing the same if it's way out of spec. They can be cleaned and flow matched which is all you really need. You guys who think you can rebuild these things right without the right equipment will pay later.

[Britwrench]

As Superman said, you are not REBUILDING it, you are cleaning it, there is a big difference.

[stokedforlife]

Very simple to rebuild, just take your time

[Alan L]

I have rebuilt several. Last one a couple of months ago. And there are kits - Salvox (UK).
I even made a new metering piston for one. They are very do-able.
There are threads on rebuilding them on this forum. I have posted a couple previously for my 930, but there is at least one SC one too, I am sure.
But I would first diagnose as others have stated, that the FD is the issue.
Alan

[pkabush]

Originally Posted by Brent 930

Measuring the flow rate by draining fuel in a cup is crude at best even though it will tell you if one isn't flowing the same if it's way out of spec. They can be cleaned and flow matched which is all you really need. You guys who think you can rebuild these things right without the right equipment will pay later.

Crude at best ? It’s the recommended method straight out of the factory Porsche shop manual and it’s extremely accurate and straight forward.
There are no flow testing requirements from the F/D

Your statements are completely inaccurate and contradict what this forum is all about.
Although they have tight tolerances and precise metering slits they are quite easy to rebuild. And as Allan stated, quality rebuild kits are readily available on eBay for under $100. The first time I rebuilt one it took less than an hour once it was off my car. I followed JFairmans excellent article. It can be found on the 930 forum. I haven’t seen Allan’s write up but, if it’s anything like his others I’m sure it’s great.
This is a job that any novice mechanic can easily accomplish.
The key for me was to have a clean work space to keep all the small parts organized. I put a old white sheet over my work table.

[Alan L]

Originally Posted by Brent 930

Measuring the flow rate by draining fuel in a cup is crude at best even though it will tell you if one isn't flowing the same if it's way out of spec. They can be cleaned and flow matched which is all you really need. You guys who think you can rebuild these things right without the right equipment will pay later.

This is total rubbish. The porsche manuals tolerate a 10% variance between injector flow rates as an acceptable result. If you have the patience and time you can do them much better than that. I aim for around 2%. But if you are paying someone to do this stuff, it all adds cost. This stuff is not hard to do.
I have done several FDs (my own) and plenty here have done them also.
Alan

[RarlyL8]

You do realize this thread is 17 years old, if the OP hasn't fixed the problem by now he has a lot more problems.
Knowledge experience skill proper tools and quality replacement parts must come together to achieve success rebuilding these. Yes you can do it but it's not for everyone.

[Alan L]

Nope.
Thanks Brian.
He is probably driving something else now. Meantime we are still stuck with our clunky old 911s.
Alan

[gsxrken]

I never mind when an old thread is bumped as there is so much knowledge buried in the PP repository, but it is amusing when posters don’t realize it and try to engage earlier posters from a decade ago.

[pkabush]

Originally Posted by RarlyL8

You do realize this thread is 17 years old, if the OP hasn't fixed the problem by now he has a lot more problems.
Knowledge experience skill proper tools and quality replacement parts must come together to achieve success rebuilding these. Yes you can do it but it's not for everyone.

😂 I guess I should start paying attention to the date stamps

[HaroldMHedge]

I realize this is an old thread but a friend came across rebuild instructions at Precision Machinery (CIS-Jetronic dot com) for rebuilding an alloy fuel distributor.

Repairing the CIS Jetronic Alloy Adjustable Bosch Fuel Distributor
https://cis-jetronic.com/public_doc/07.3-0997-06.pdf

Porsche Fuel Distributor Rebuild Parts
https://cis-jetronic.com/index.php?rt=product/manufacturer&manufacturer_id=34

They also have a good Technical Data Set
https://cis-jetronic.com/index.php?rt=product/category&path=65_66