cis help please!

dwil · 09-02-2001, 07:17 PM

my 77 2.7 will start and idle, rev ok but when i let it return to idle the airflow lever that controls the fuel distributor starts oscillating a few times per second,
then dies. i have just replaced the airbox,
boots, intake gaskets, vac hoses. system pressure is 72 lb, warm control pressure is
42 (this flutters wildly with the above oscillation before the car dies) i have checked spark timing, substituted the entire
igntion system, took the fuel distributor apart and put in new o rings. Could it be the
fuel pump or accumulator not holding pressure? Advice from somebody that been there would be greatly appreciated. Thanks

Superman · 09-02-2001, 08:01 PM

Sounds like your troubleshooting has been fairly complete. Your findings about the wildly fluctuating fuel pressures are intriguing. These CIS cars have a mysterious idle surging problem that no one seems to have figured out. Perhaps you have.

I sure doubt that your ignition system could be causing this. I think your CIs is purely mechanical and besides, this is fluctuating fuel pressure we're talking about. So, I'd suspect something like a plugged or vibrating fuel line, fuel accumulator, fuel pump, like you said. Fuel pressure is what provides resistance against the actuating arm under the fuel distributor. So, this certainly is what is causing the sensor plate to oscillate.

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'83 SC

stlrj · 09-05-2001, 08:00 AM

Fast oscillations, several times a second, at idle usually mean a vacuum leak, where as a slow oscillation means an over rich mixture.

I would keep looking for a vacuum leak somewhere. Something as simple as removing the air boot and putting it back on carefully could solve the problem.

Cheers,

Joe

[This message has been edited by stlrj (edited 09-05-2001).]

[This message has been edited by stlrj (edited 09-05-2001).]

wckrause · wckrause's Garage

If you're system pressure is stable, but the control pressure is fluctuating wildly, I would suspect the Warmup Regulator. Disconnect and plug the vacuum line to the WUR and see if the fluctuations are still there.

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Bill Krause
'79 911SC Euro
MY PELICAN GALLERY

Jdub · 09-05-2001, 08:42 AM

Isn't there also a problem with the plunger in the CIS unit sticking, and then causing the fluctuation?

Have you run the bejabbers out of your car with a 20oz dose of Techron? That cleared up my injection-side problems pretty quick. That plus a removal of the boot and a cleanout of the sensor plate, etc of any oil (thanks to my overfill of the car!!!).

Jw

Superman · 09-05-2001, 08:54 AM

I think dwil says the control pressure flucuates with the sensor plate oscillation. This makes sense since it is fuel pressure that provides the resistance against of the plate against the wind. And if control pressure is fluctuating, then we found the problem. Also, I agree that the likely culprit is the WUR.

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'83 SC

dwil · 09-09-2001, 08:23 PM

It ended up being the thimble shaped
restrictor in the top of the fuel distributor
was bent. I had an old distributor that had this part still intact, put it in and now the
fuel pressure is stable. The damaged part was allowing too much movement of the piston
valve.
I want to thank all you regular posters, I have learned a lot from you in the past year and to pelican for a great bbs.