Juan S

Hi all,

I continue with the rebuild of my 1980 porche 928S Euro car 4,7 (M2811 engine),
With regards to the CIS system, I executed the following tasks:
- Fuel distributor rebuilt
- New fuel pump/filter
- WUR rebuilt
- New injectors
- New check valve
- Timing set

The CCP, HCP and System pressure are within spec according with the gauge readings.
But the System pressure will not hold for more than 10 minutes
The issues I expierience is dificult start when the engine is hot and rests for more than 15 minutes. It will take a lots of cranking to get it start.
I suspect it is related to the system not witholding the pressure.
My only guess is a defective fuel pressure accumulator but when I looked at the rear wheel and nothing is there.. could it be that my 928 doesn't have one? (I doubt it...) then what?
And on a separate note, my iddle screw has no efect at all; I can secreew it all the way in and out and no effect in the idlle of the car. What could be the cause? could it be related with the throttle body or it has to do wit the throttle cable adjustment itself?

I really appreciate you guidance in both issues.
As always many thanks in advance!

Juan

gbgastowers

Were the rebuilt WUR and FD calibrated and verified to be in spec to original factory settings after the rebuild was completed? Also are the part numbers a match to what it left the factory with? That’s important. Gunar

Juan S

Hi, yes, both rebuilt by a specialized shop and both original parts.
Many thanks

GerritD

Hi Juan,

I have the same 928S euro with the CIS
You need to have a fuel accumulator otherwise you will have hotstart issues.
If pressure is not holding, it could be that valve in your fuel pump

Petza914

CIS hot start issues are usually a bad temp sensor that's flooding the motor with fuel from the cold start valve even when it should be or the fuel in the engine bay vaporizing from heat when sitting.

To test the temp sensor and cold start injector, unplug the electrical connection from it and see if it behaves any differently with it unplugged.

If the fuel is vaporizing, holding the throttle all the way open as you crank it brings in liquid fuel to force the vaporized fuel out of the system.

Juan S

Ok, many thanks. Could the fuel accumulator be in other location than in the rear wheel??

Petza914

Not that I've ever seen.

Should look like this


This was the old filter and accumulator setup in my 79 CIS car before replacement with new components.