Fuel Distributor: no Fuel pressure on the outlet ports

[Housemarkee]

Hello all, i got stuck in my 930 project.
The car is a 1987 SC Turbo ROW

I rebuild the engine and now it comes to the final start after some years of restoring this car.
Weeks ago I installed the engine in the car and try to start, but without success.
The following steps I renewed or troubleshooted since:

- new fuel tank (after 3 years, the old fuel was weak and rusty)
- new fuel-pumps with the identical original specs
- new fuel-accumulator and filter-cartridge
- measured the flow rate, the system, control and residential pressure (all in specs)
- checked the injectors (some spray ok, some not)
- new fuel injectors

- fuel-head rebuild (iron cast version) with new gasket rebuild-kit
-- tested the fuel outlets (4 outlets delivers fuel with ok pressure, 2 send nothing)
-- double checked the rebuild and figured out an error with a wrong inserted
fuel-cylinder

- fuel-head rebuild #2 (correct the cylinder-position to the correct ports
-- checked the outlets with running fuel pumps (all 6 ports are wet, but no pressure)
-- used that time less loctite 574 because there was to much inside the 1st time
-- all adjustable ports reinstalled and with 6 1/2 rotations installed and precise
measured

- fuel-head rebuild #3 (new gasket kit, all in a clean room with more focus/time)
-- checked the outlets with running fuel pumps (all 6 ports are wet, no pressure)
-- same behavior like the 2nd attempt

Now I can´t believe that the fuel distributor could be the problem...
I bridged the WUR but no symptoms of more pressure. The shims under the pressure-valve in the fuel-head are tested with 2 shims and without...same behavior.

Did any of you had an impulse for me for further investigation.
I´m lost

Thanks for your help
AJ

[flightlead404]

what does "without success" mean?

be more specific

[Housemarkee]

Originally Posted by flightlead404

what does "without success" mean?

be more specific

Hey, yea it means, that the engine did not crank at all.
No fuel pressure, just wet ports...not enough to release the injection-valves to fuel the cylinder.

[flightlead404]

Originally Posted by Housemarkee

Hey, yea it means, that the engine did not crank at all.
No fuel pressure, just wet ports...not enough to release the injection-valves to fuel the cylinder.

If the engine didn't crank I would not expect there to be any fuel pressure.

Engine cranking creates vacuum in the intake manifold, which displaces the air sensor plate, which closes the safety swtich on the back of the airflow sensor, which grounds the fuel pump relay, which turns on the fuel pumps, which creates the fuel pressure.

and the hip bone is connected to the eye bone

[Housemarkee]

Originally Posted by flightlead404

If the engine didn't crank I would not expect there to be any fuel pressure.

Engine cranking creates vacuum in the intake manifold, which displaces the air sensor plate, which closes the safety swtich on the back of the airflow sensor, which grounds the fuel pump relay, which turns on the fuel pumps, which creates the fuel pressure.

and the hip bone is connected to the eye bone

You´re right, wrong description.
my fault.

But you see my steps of troubleshooting the subsystems.
for further information: after the first fuel-head rebuild the engine starts with additional "Startpilot" spray and runs a short time on the 4 cylinder that provided fuel.

So, valve timing, and compression seems ok.
But my problem seems the missing fuelpressure at the fuel outlet ports.

any idea?

Thanks for your help

[Schulisco]

The fuel distributor is a highly sensitive and heavily precise machined part which urgently needs to be overhauled by a specialist fpr CIS. When you're not experienced in doing that I recommend to contact a CIS specialist to let it overhauled. I let my FD overhaul from dr-mengenteiler.de, but there are more specialists available in Germany. Also I recommend to send the warm up regulator, the injection valves and even the sensor plate housing as well for a check. This all works together and if only one part of the CIS is not in spec you're chasing for issues for a long time and going nuts over time and in the end you're frustrated by the car due to poor performance and guzzling (unecessary) fuel ...

BTW: The plunger above lacks of rubber O-rings for every port...

Thomas

[RarlyL8]

Are you installing a new metal diaphragm when rebuilding the fuel distributor? A damaged diaphragm will produce similar symptoms.

[Alan L]

Yes - there should be O rings on each metering port. Otherwise the thing won't work.
Also I am not clear where you used Loctite. I use none. I wonder if you are sealing the two halves with it, but there should be none inside there.
Alan

[reclino]

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/848849-barn-find-1986-911-turbo-11.html
See photos here back when I was rebuilding my fuel distributor.
Its a US spec lambda unit but I show the O-rings I installed on each port of the center section.
Your use of loctite may also be causing issues, I thought this was a simple metal shim depending on perfect surface finish to seal, truly a challenge for rework.
David
Performance EngiNerding

[Housemarkee]

Yes, I put in new Diaphragm, gaskets and real short amount of flange sealant on the two halves of the FD.

Today I phoned with an old Merc Mech.
He told me that my upper pressure could be the problem when I install a new and empty Fuelhead with the fullinitial pressure of the 2 fuel pumps.
He suggested that I should start filling with only one pump connected until the system is flooded fully. Than the hydro balanced fuel pressure should be working. Seems like the Pressure on the top was to high.
My plunger had a massive pressureload, I felt it when I was pressing the AirFlap against the plunger. That felt really heavy under load, but for me surprising that nothing came out of the 6 outlet ports.
I´m not im my garage this week, but will give a feedback until I found time to test it.
Thank you all for your Inputs and help.
regards AJ

[Alan L]

The plunger/airplate pressure load comes from your WUR pressure. Have you measured it? there may be a problem there. The plunger/airplate pressure should be firm, but easily moved. It is the airflow over the plate that moves it. Should not be rock solid firm.
Alan

[gorskined]

AJ
i am by no means an expert but i have spent 100s of hours on my fd and wur and associated fuel lines and injectors. Mostly trial and error but i have learned a lot. eventually i sent them both out to be professionally rebuilt. and still have the same intermittent issue as before.
If you wet sand the two faces of the fd with 1000 grit wet sandpaper then finish with a 1200 sand in a circular motion flat on a piece of glass you wont need to use sealant. if you do use sealant use sparingly and cut with acetone a pea size dot mixed with a table spoon of acetone in a small ramakin is more then enough, apply with a very small paint brush . i assume your pin hole on the diaphragm is lined up correctly if you use sealant you risk clogging this pin hole.
I am still ironing out some of my intermittent fuel system gremlins. make sure your hard fuel lines exiting the fd to the injectors are clean. I kept picking up what looked like pepper flakes at the injectors and i soaked and high pressure washed my injector lines, eventually i found a nos set of hard lines. That stopped the pepper deposits in my injectors . you will be surprised what breaks down off any reused hard line all it takes is a flake the size of a grain of salt to enter your fd and you are asking for problems . are you using an inline strainer at your fd. if so check frequently to see if it picking up any debris. pelican part sells a inline strainer that fits on the fd part # 000 074 60 86.. i only plan on using it until all the bug are cleared up its a very fine mesh and will eventually restrict flow.

Good luck keep us up-to-date

Regards Ned

[Housemarkee]

Projectupdate:

The fuelhead works and sprays now through the injectors in a clean way.

What I have done:
- cleaned out the hard fuel lines in carb cleaner after a wellness bath in the ultrasonicpool
- rebuild the main fuel line from the filter to the fuelhead (crispy hose, broken fitting)
- rebuild the WUR. The diaphragm and the filter were cloaked and muddy. So a warm visit to the ultrasonic huttub and a rebuild kit helped. After that a vacuumcheck shows that the rubbergasket were ok
- temporary installed a pressure regulator to build up slowly pressure until the whole system were filled up.

at least... Not starting.
but back to the beginning and tomorrow will check the fuel pressures again, the spray amount of the injectors, and the ignition timing cyl1/TDC and so on.


my final thoughts about rebuilding a fuelhead.
Its not impossible, but it needs a learning curve.

suggestions:
- make marks on the FH and photos
- make a sketch and number the ports according to the cylinderports 1-6
- measure the nozzle deep with an caliper and wrote the infos down in the sketch (you´ll need it badly for reassembling) This is only for adjustable Fuelhead. I´m not sure, but I believe only the IronCast ones had this, the Aluminium ones may not.
- working in a nearly cleanroom environment
- using different boxes for each parts per cylinder port (not to mix up the springs)
- if the upper and lower halfs of the head are fully smooth, dont use any flange sealant/fluid gasket. If not use LOCTITE 574 but only so much that you can see it shine. When you see the orange color of the loctite, its way too much. This stuff will cloak your fuelhead in time. attention!
- focus on the tiny hole and position it to the WUR bore hole (look at your disassembling photos)
- use lil amount of weaponoil to install the plunger for a smooth slide
- reassemble the head with a torx wrench in criss cross patterns (pictures can you find on google or here in the forum search)

additional a nice 928 source for fuelhead infos
928srus. com /pages/928-k-jetronic-cis-distributer-rebuild

Thanks you all for your help and inputs.
I like the community for getting and giving impulses

Stay healthy
Regards AJ

[Alan L]

Sounds like progress.
It doesn't matter if you mix the FD springs up, you will end up recalibrating it anyway. And the port numbering doesn't matter. Any port will do for anywhere. There is no injection timing - CIS. Very simple system.
Regards
Alan

[Housemarkee]

Originally Posted by Alan L

Sounds like progress.
It doesn't matter if you mix the FD springs up, you will end up recalibrating it anyway. And the port numbering doesn't matter. Any port will do for anywhere. There is no injection timing - CIS. Very simple system.
Regards
Alan

Thanks Alan,
yea I read in different sources about the springs and the shims inside. Some told that they clearly arranged because they are "measured by bosch in the assembly process", some others ignore it.
Lil mystery... but i thought better prevention than aftercare

AJ