74 911 cis help

[mb911]

I am working on a 74 911 with a 76 cis set up. This car has sat apart for 8 + years and the owner passed away during that time and the new owner only knows tidbits of info. I spent the last 9 months slowly putting back together for the new owner. The owner did not want me to tear the engine apart as much as I felt it should have been as the engine sat outside under a tarp for those 8 years. I was able to get it to start and has good oil pressure but it only starts after a couple of 25 second starter crankings and then moving the metering plate. It starts and runs for a few seconds then and will sputter and die. I finally was able to get it running after nursing for a few minutes and was able to get it to idle and drive down the driveway and back for about 30 minutes. I shut it off and it restarted fairly well while hot.

Fast forward when cold it starts horrible. Any advice?

[ossiblue]

Could be several factors. Because it doesn't fire-up immediately, even for a brief few seconds, the Cold Start Valve is suspect. Even a CIS with massive air leaks and poor fuel pressures will fire, briefly, if the CSV is functioning. That would be my first area of investigation.

The 25 second cranking also indicates a faulty CSV, especially if you do not smell fuel during those times. The CSV only injects fuel during cranking and, in your case, a functioning valve should have been noticeable and, possibly, been flooding the engine. If you, in fact, did detect a strong fuel smell, then you dodged a bullet in risking hydro-locking the cylinders.

The duration of cranking also points to fuel delivery problems, possibly. Did you prime the system before trying to start? Try lifting the sensor plate in the intake with the fuel pump running--only until you hear the injectors vibrate. Does it now start? If so, the loss of residual pressure or, if this was the first start after assembly, the system pressure needed to be primed. If this is the case, your residual pressure is suspect. Could be from a bad check valve in the FP, check valve in the Fuel distributor (less likely), or bad fuel accumulator. However, your success on warm starts tends to point away from the accumulator, but we don't now how long after the engine was shut down, warm, that your successful restart happened.

Once started and running, your description seems to indicate a very lean condition. First order of business is to test the fuel pressures with a set of gauges--system pressure, cold control pressure, warm control pressure, and residual pressure. Get those in spec first. Once those are known to be good, move on to air leaks.

'76 was the first year that CIS had the added devices to assist a cold start--Auxiliary Air Valve and Auxiliary Air Regulator, for example. Either or both of those can cause your problem if they are not functioning properly. Additionally, you may have air leaks in any of the hoses or fittings of the system. All of these, added together, can seriously compromise the running/starting of CIS. There are many threads on testing for air leaks, should you need to do that.

All the above is assuming your ignition, timing, and valve adjustments are in spec.

[75 911s]

Not a CIS expert but sounds like the usual suspects in regard to cold start. You need to test pressures with a CIS fuel pressure gauge, then test the WUR and check the Aux Air Valve. There's a specific system for cold start in the CIS that will help you isolate the problem. Search CIS primer (external website) , testing WUR, AAV (auxiliary air valve) and cold start and you'll find myriad threads on the subject.

[al lkosmal]

Ben, I would recommend that you do the pressure testing for cold/hot, system pressures. There are a few things that can cause cold starting issues. Cold-start injector not working, WUR not properly controlling the fuel pressure at start or cold running, Aux air valve not providing idle air......vacuum leaks and on and on...but the pressure test can help to pinpoint the problem.

Even prior to the pressure test, I would verify that the Cold Start Valve (via the thermotime switch) WUR and AAR, etc are receiving 12V at start.

regards,
al

[mb911]

Interesting comments . I maybe wrong on the year of CIS as it does not have an AAV or an AAR. I will have to post numbers of what I have. I suspect there is an issue with the thermo time switch as there where some wiring issues there from the PO. This was really a basket case with no less then 20 people with there hands in it prior to my agreeing to take on the project waaaaay to cheap. I will get some pressures this week and post for sure. I also do know that supposedly when it ran years ago that it was hard starting both cold and hot .

That said here is the story. I have the original CIS off of the car as once installed in the car it leaked from every orifice and the owner didn't want to spend the money to rebuild everything. So I put a WTB ad out here and bought a "known" working CIS from a member here. That included the fuel distributor, injectors, air box, WUR, TB, but not the accumulator or fuel pump . The thermo time switch was original to the car with the wiring etc. This system does not leak and looks to be in fairly good condition. I did bleed the system once installed..

I probably need to post some pictures of what I have. This is a puzzle that just never ends. In hindsight I should have not taken the project on but felt like the car would just be destined for the junk yard had I not taken on the project.

I appreciate the insight already and I will share the info as I know more

[ossiblue]

Originally Posted by mb911

Interesting comments . I maybe wrong on the year of CIS as it does not have an AAV or an AAR. I will have to post numbers of what I have. I suspect there is an issue with the thermo time switch as there where some wiring issues there from the PO. This was really a basket case with no less then 20 people with there hands in it prior to my agreeing to take on the project waaaaay to cheap. I will get some pressures this week and post for sure. I also do know that supposedly when it ran years ago that it was hard starting both cold and hot .

That said here is the story. I have the original CIS off of the car as once installed in the car it leaked from every orifice and the owner didn't want to spend the money to rebuild everything. So I put a WTB ad out here and bought a "known" working CIS from a member here. That included the fuel distributor, injectors, air box, WUR, TB, but not the accumulator or fuel pump . The thermo time switch was original to the car with the wiring etc. This system does not leak and looks to be in fairly good condition. I did bleed the system once installed..

I probably need to post some pictures of what I have. This is a puzzle that just never ends. In hindsight I should have not taken the project on but felt like the car would just be destined for the junk yard had I not taken on the project.

I appreciate the insight already and I will share the info as I know more

Thanks for the feedback as that is essential for assistance.

Not having the '76 or later warm up devices is odd and it will be interesting to see just what you have, including the numbers off the WUR and FD. Perhaps ROW engines of that year did not have the devices, I don't know.

Still, your cold starting symptoms seem to be related to a non-functioning CSV.

[75 911s]

74 and 75 do not have an AAV/AAR. Cold start is helped along with a hand throttle that pulls and holds the accelerator cable. The hand throttle stopped at 76. If you can cold start by holding the accelerator pedal, then perhaps that's the issue. Find out the year of the replacement CIS.

[ossiblue]

Originally Posted by 75 911s

74 and 75 do not have an AAV/AAR. Cold start is helped along with a hand throttle that pulls and holds the accelerator cable. The hand throttle stopped at 76. If you can cold start by holding the accelerator pedal, then perhaps that's the issue. Find out the year of the replacement CIS.

The car in question does not have a 74/75 CIS, but a later version that was supposedly from '76 which should have those devices. Doesn't really matter as the CIS he put on doesn't have them. You're correct about the hand throttle, but that was tied into a micro switch that activated the CSV. If the new CIS doesn't have the micro switch, the CSV would be inoperative which could account for his problems. We need to see the set up he has on the engine.

[mb911]

Here is some info. Thanks for the help

[boyt911sc]

Ben,

It would be easier to fix your CIS starting and running problem/s if you have the right CIS parts including the missing ones. First, did you know that you have the wrong WUR? The FD is correct but the question is it in good working condition? I have boxes of AAR and aluminum vacuum tubes that are just sitting and collecting dust in my garage. And other parts you might need. I will donate some of these to your project.

I feel good since last Saturday after I bought a box full of assorted WUR's at Hershey Swap Meet from a vendor. The vendor is also a well known Porsche shop but decided to give up on CIS work. And sold this valuable lot as scrap metal. I just could not believe my luck and wish to share it with others.

This is what I brought home from Hershey last weekend:





PM me at your convenience. Do you have pictures of the right side (cyl.4-5-6)? How about the rear view of the motor? Thanks.

Tony

[mb911]

Originally Posted by boyt911sc

Ben,

It would be easier to fix your CIS starting and running problem/s if you have the right CIS parts including the missing ones. First, did you know that you have the wrong WUR? The FD is correct but the question is it in good working condition? I have boxes of AAR and aluminum vacuum tubes that are just sitting and collecting dust in my garage. And other parts you might need. I will donate some of these to your project.

I feel good since last Saturday after I bought a box full of assorted WUR's at Hershey Swap Meet from a vendor. The vendor is also a well known Porsche shop but decided to give up on CIS work. And sold this valuable lot as scrap metal. I just could not believe my luck and wish to share it with others.

This is what I brought home Hershey last weekend:





PM me at your convenience. Do you have pictures of the right side (cyl.4-5-6)? How about the rear view of the motor? Thanks.

Tony

Wow great offer. I will pm you. Here are some pictures

[boyt911sc]

Ben,

Do you have some pictures of the following?

a). Base of intake runner #5 for AAR mounting.
b). Throttle body ID number.
c). Air flow meter ID number.
d). How is the decel valve connected to the throttle body and WUR?

Why is the WUR not mounted on the plate intended for WUR? What is the ground wire for? We will make this engine run again as good as expected. Keep us posted.

Tony

[mb911]

Will do..

Wur is just removed for part number picture. The black wire was just how the cis came.

I will work on getting you more info as time allows at baseball with kids. Probably tomorrow afternoon.

Thanks again

[mb911]

Emails and pms sent. Thanks everyone for your help

[mb911]

Tony has my parts and is currently working on testing them. Thanks Tony for the help

[boyt911sc]

Ben,

I got the package and will do the testing either tonight or tomorrow. You should have kept the air flow metering unit and sent only the FD and WUR. Took a picture so I would remember what to ship you back. Specially the fittings. I forgot to tell you to remove all the fuel hose fittings. Less things to remember when you get older like me.



Tony

[mb911]

Originally Posted by boyt911sc

Ben,

I got the package and will do the testing either tonight or tomorrow. You should have kept the air flow metering unit and sent only the FD and WUR. Took a picture so I would remember what to ship you back. Specially the fittings. I forgot to tell you to remove all the fuel hose fittings. Less things to remember when you get older like me.



Tony

My apologies.. Thanks again for helping.

[Knockdown]

WURderful score at Hershey and offer to help out!

[boyt911sc]

Ben,

I was able to do the tests for your WUR and FD today and here are some pictures to share.

Good news: Fuel distributor is good but the system pressure needs some adjustment. It has only 65 psi. Spec. is between (65~75 psi.). Install additional shim to bump it to 70 psi.

Bad news: You have the wrong WUR and it does not work. The fuel does not flow freely through the screen. The cold control fuel pressure is too high to get the motor to start. The CSV was the only source of fuel during your attempted starts that lasted a few seconds.

You will need a good working WUR plus the missing CIS components that were removed from the system.


Cold control fuel pressure (above) shows 55 psi. That is a heck too high for CCP.


Close up shot of the pressure gauge (above) at 55 psi. for CCP.



Cold control fuel pressure with the pin/sombrero/springs (springs not shown in pic) removed from WUR. A good working WUR without these components would register a very low fuel pressure between 5~8 psi. This one shows abou 30 psi. The clogged filter screen is the culprit.



This fuel line fitting has to be disposed and replaced.

Lastly, would you be interested in getting a WUR-033 loaner (rebuilt and calibrated)? You could use and test it in the car and send it back to me when you are done. You are not obligated to buy it. It is a loaner.

Tony

[mb911]

Tony,

I am going to suggest that the owner purchase the correct wur from you. I will check and see if we have another wur that would be an acceptable core for you.

So his cost would be 290? We are making progress.

Thanks again