911 sc cis residual pressure

[T77911S]

you need to pull the plunger out and clean it.
dont drop it.

THAT will make it rich
not sure how it is running or idling

[leonardo911sc]

Good day Phil.

After moving the plunger fully up and down many times the plunger was always returning to bottom position and in touch with sensor plate arm.

If it is stuck again i will remove the FD and investigate further. No further actions for now. My best man drives the car on daily basis without any issues.

He told me that he battled with a mercedes amg 55 head to head from a stop light up to 180 km. Mercedes took over afterwards.

Not bad for a 40 year old car!

Thanks

[Showdown]

Congrats!

Though a bit of a Rube Goldberg contraption, CIS, when understood and made to work properly is pretty clever and the feeling of conquering it is downright glorious.

[T77911S]

there should be NO play in the sensor plate when the FP is on.

[mtc911]

How much pressure should be maintained in the system after sitting for several hours/overnight? I have run all the tests, have the CIS gauges, etc...have found multiple faulty parts during my troubleshooting....I have this thing dialed in almost perfectly but I still just have a little trouble starting it after sitting overnight. It will start but seems like a few too many turns of the starter than what it should be. It's very hot here right now so I don't think the TTS is even in play. Hot starts and starts after a few hours...all great...idles great..runs great....I may be chasing perfection at this point...but just trying to determine why it struggles after overnight.

Should there be pressure in the gauge set after sitting overnight?

Fuel Accumulator is new, WUR is new....ALL pressures checked well within specs..just don't know if there should be remaining pressure overnight...can't find anything on that.

bone stock 1980 911SC - I did replace the fuel pump and filter about 5 years ago...ordeed a check valve for the pump just to try that since its cheap. Havent installed that yet.

Thanks.

[keoniahlo]

Originally Posted by leonardo911sc

Let me reply to the above.

Although the engine now starts every time anytime, at cold starts the smell of rich mixture was noticable.

A couple of hours ago i went for a routine service before i deliver the car to my best man. Lubricant, oil filter and air filter.

When i removed the air filter i went and pushed up the sensor plate. It took about 5-6mm until the resistance of the plunger was felt.

Repeated the push up a couple of times to realize that the plunger was not resting on the sensor arm completely.

After about 10 times of moving the arm up and let it relax it finally rests on the arm and resistance can be felt from the begining of the lift.

Now gas smell is also gone at cold starts.

This is also the reason why in the begining of this thread i mentioned that the engine will not start after 9 hours but it may start after 2 days!

I suppose the plunger eventually would rest on the arm over time and gravity effect.

So my culprit was a combo of CIS components not working properly.

Now officially this case is solved.

Thanks everyone for your assistance and knowledge passed.

My hunch is that your piston might be sticky as you mentioned, and it's not coming all the way down overnight. This would simulate an enrichment position within the fuel distributor, so you might get a blast of fuel immediately when the pump fills the chambers. Just thinking out loud.