Still wont run well

[Kelly Bell]

I am having some problems keeping my 75 911 running. Now, mind you it had sat for 9 years before I got it. I have replaced:

new CSV
Termo time switch
all Fuel injectors
all fuel injector hoses
rebuilt fuel distributir
new fuel pump
new fuel hoses
new fuel tank
new dist cap
new rotor

The thing will start (I think off the CSV) and run strong a few seconds, then will run very slowly, as if on one or 2 cylinders, and conk out. It will start right up again, tho (on the CSV, I suspect) and do the same thing. When I run back and push up on the control lever, I can keep it runing, altho it pops a bit.

Also, I have noticed that, when I adjust the idle mixture screw, it seems to "bottom out" and I can never get the injectors to spray. I understand you are supposed to get the FIs to spray, then back off just a bit, until they stop.

Could it be that I am starving for fuel b/c the idle mixture is not letting the FIs come on?

Confused in Atlanta

[Kelly Bell]

One more thing, I have not replaced the WUR. Do you think I should?

[Rex Walter]

Kelly,

I'm bumping you up to the top so that the CIS experts might respond. Until they do......If you push up on the control lever, you are letting in more fuel. If this makes it run better, maybe you should try richening the mixture by turning the allen screw clockwise a little - you have the tool for this don't you?

I'm not an expert on CIS, but I've never heard of setting the idle by getting the FI to spray. You should have a hand throttle between the seats. Pull up till you get the RPMs you want. Set the idle screw after it warms up (If you can get it run that long).

You didn't mention siphoning out the fuel and getting fresh fuel in the tank - did you do that? I'd also pull a fuel injector and put it in a bottle, turn the key to the run position, and go back and lift the control lever to see if it sprays.

Let us know how you are doing - Rex

[Kelly Bell]

Thanks, Rex,
I have turned the idle mixture screw as far in(clockwise) as I can. I thought as I turned it, that I would eventually see the FIs spray, but the screw "botomed out". ie would noy turn further.

Yes, I have fresj fuel in her as well. there is very littel in the fule delivery system I have not changed, except the WUR.

I have put a FI in a jar and lifted the control lever and it sprays quite well.

Thanks Rex!

[Kelly Bell]

Sorry for the mispellings! LOL..............

[Ruff1]

I had the same problem and mine was a dirty fuel filter and the tank was redone but the return line was block with the tank sealant. also check if your cis is building enough pressure by removing the airfilter and checking the flap.

[Kelly Bell]

Thanks! Whatr do you mean "the flap"???

[Rex Walter]

I think "the flap" is the control lever or air sensor plate.

The idle screw will only let in air. I guess if you let in enough air, the air sensor plate will rise and fuel will start to flow. Turning the screw in (clockwise) will do just the opposite - you are going toward lower idle, less air, less fuel. I would just use the hand throttle until you get it run long enough to set the idle.

See if your injectors are getting fuel by doing the test I described above - it only takes a couple of minutes to set up and run.

Rex

[Kelly Bell]

Hi Rex,
Yes, my injectors spray well, they are all new.

[Hladun]

Have someone who knows what they're doing set up your system.

[Paulporsche]

Hladun certainly makes sense. It could be many things, including the WUR and the AAR (if you have one). You should check your fuel and control pressures, and make sure the sensor plate is correctly set, and the plunger and plate move freely.

BTW my 80 engine recently exhibited that warmup popping. Turns out I had a broken head stud which allowed one cylinder to run lean until things warmed up.

[MobileWrks]

I just did a turbo with a fuel dist rebuild. I Changes all sorts of thing just to better his car since it sat for 3 years. Put a set of gauges and read the pressures, and let us guide you. I had to shim the fuel dist cause the pressures were a little too low, once i did that, WAR final adjusment and BOOM, boost hit hard and RAN LIKE A CHAMP....

[MobileWrks]

FYI, i put MSD and blaster coil cause he also had a intermidiate short, ran but not well enough..

If you have a hard time, feel free to call me CA time... LOL

[ghnat]

Kelly,

Looks like you have been hard at work on the car. I wish I could help, but I know nothing of CIS. How is the body shaping up?

[Kelly Bell]

Thanks, all. I know I could take it to a professonal, and I may still, but the whole point of this excercise is to to the work myself.

I think I am ging to change out the WUR. I have a Porsche FI book and I have ben reading that the WUR controls the pressure from ABOVE the Fuel dist. control plunger. which makes sense. I would assume mine is bad, and that could be the problem that is causing a lean cold running mixture.

I will let you know what happens, I saw a new one on the internet for $238, I'm gonna buy it.

[Kelly Bell]

BTW, Greg, I emailed you

[Rondinone]

What are you using for fuel injector hoses?

[Kelly Bell]

I used cohline hoses, and replaced all six.

[Rondinone]

Originally posted by Kelly Bell
I used cohline hoses, and replaced all six.

When you pull out an injector, and press up on the air sensor plate, do the injectors spray continously or do they pulse? Do they pulse at low flow rate?

[Ruff1]

sorry i have been away and didnt get back to you faster. Remove the air filter and you will see a flap a metal arm sort of if you press on one side the injectors should spray. Know turn the key and leave it on and go to the back of the car if the flap doesnt move and is under pressure when you try to push it up your dist is ok. know if it movesyou have to rebuild your fuel dist. get somebody who knows what they are doing to rebuild it. I learned the hard way and lost $300 and then bought a used one for $275. The guy who rebuilt it said he knew what he was doing he said it the same as vw and audi. DO NOT LISTEN TO THEM IT IS A PORSCHE AND NOT VW OR AUDI! Let me know what happens.