going CIS crazy!!!

[jinos]

I'm gettin so frustrated with this CIS crap. ahhhhhhhhh!!! I had a hot start issue so I worked from the bottom up and replaced the following: fuel pump, check valve, fuel filter, fuel accumulator, and fuel frequency valve. After all replacements my 911 74 with a 3.0 still won't start after running. It fires up with no problem when cold but won't after 10 minutes. What the h#$l is wrong with this? I'm so fed up with this right now. Any help is greatly appreciated.

[vash]

are you just changing parts? do you have the CIS gauges? i dont have my book in front of me, but i seem to remember a system of test you do (pinch off lines, etc) that can narrow it down to a specific problem. it has been maybe 5 years, but i seem to remember that i found my WUR to cause my hot start problem....again, i am at work and dont have my notes in front of me.

[Gunter]

When installing the 3.0, are you running the full Lambda? OX sensor?
Correct ECU for the year of your 3.0?

For hot-start issues, the Check valve and acummulator is suspect even if new.
Fuel system residual pressure check would tell you if the pressure is maintained.

[Scott R]

If the pressures are in check, look at the sensor plate height when hot. I worked on one that was set too low and when hot the plate would not lift enough to get the engine started.

[jinos]

What's the WUR? Is this the fuel distibutor? It's the full CIS that came with the motor which is an 82SC. I didn't know that SC's had ECUs. The previous motor was also a 3.0 from a 78 but was blown. Both motors had a cat-bypass so the O2 was capped. Thanks you guys.

Hi Scott,
I'll take a look at the sensor plate later today. Thanks.

[Scott R]

Originally Posted by jinos

What's the WUR? Is this the fuel distibutor? It's the full CIS that came with the motor which is an 82SC. I didn't know that SC's had ECUs. The previous motor was also a 3.0 from a 78 but was blown. Both motors had a cat-bypass so the O2 was capped. Thanks you guys.

Hi Scott,
I'll take a look at the sensor plate later today. Thanks.

There should be an ECU and a relay under your passenger seat. I can't imagine that it would be missing as the 82' would run terribly without it. For your year that ECU takes a signal from the O2 sensor and then controls the frequency valve. If it were missing the FQ valve would be inop and the car would barely run.

[jinos]

I replaced the freq valve because it was leaking fuel and could smell the burnt valve. I'll check the ECU. Thank you once again.

[jinos]

One more note. The O2 sensor was always capped off since purchase of the vehicle and ran really well. You're right about the frequency valve. When it was taken out it wouldn't even start or sputter. It was basically undrivable. Are you saying I need to get an O2 sensor to run right?

[Scott R]

Originally Posted by jinos

One more note. The O2 sensor was always capped off since purchase of the vehicle and ran really well. You're right about the frequency valve. When it was taken out it wouldn't even start or sputter. It was basically undrivable. Are you saying I need to get an O2 sensor to run right?

First if the FQ was leaking check that it's plugged into the right connector. I've seen one plugged into the WUR plug before and it melts it after a few mins of driving, and of course fuel goes everywhere.

Secondly, there are two schools of thought around here on the O2 sensor. Some like to leave it disconnected and just set the system to around 3% CO and call it done. I've got some dyno sheets posted under my user ID, one run is with the O2 sensor connected and the mixture set to factory specs. The second is 3% and the O2 sensor disconnected. I have slightly better AFR's at cruise with it connected, and it made a tiny bit more power.

I don't think either way is wrong, as I've been able to run in both the configurations I mentioned above.

[T77911S]

if he put the 82 in and did not know it came with an ECU, it probably does not have one.
if it was me, i would take the CIS off the 78 and put it on the 82. actually i would use the 82 air box and runners and swap everything else. it is a much simpler system, no freq valve, no
ECU, no O2. you also need the WUR the 78. that equals better reliability.

how does it run when hot?
does it not start at all when hot?
have you tried lifting the sensor plate with the key on to prime the system?
have you checked the mixture when warm and the control pressure?

just remember, there is probably someone out there cursing carbs because they can not get them set right.

[jinos]

It runs well when hot. It just has a real hardtime starting. It sputters and then dies out. So I tried pressing the accelerator and it still dies. But after the fifth try it sputters while holding the accelerator. After pressing the gas for 5-10 seconds if revs up high and idles perfectly. It almost seems like somthing is clogged if that makes sense. Are you talking about the sensor plate on top of the air box? How do I check the mixture? Thanks.

Originally Posted by T77911S

if he put the 82 in and did not know it came with an ECU, it probably does not have one.
if it was me, i would take the CIS off the 78 and put it on the 82. actually i would use the 82 air box and runners and swap everything else. it is a much simpler system, no freq valve, no
ECU, no O2. you also need the WUR the 78. that equals better reliability.

how does it run when hot?
does it not start at all when hot?
have you tried lifting the sensor plate with the key on to prime the system?
have you checked the mixture when warm and the control pressure?

just remember, there is probably someone out there cursing carbs because they can not get them set right.

[Scott R]

Originally Posted by jinos

It runs well when hot. It just has a real hardtime starting. It sputters and then dies out. So I tried pressing the accelerator and it still dies. But after the fifth try it sputters while holding the accelerator. After pressing the gas for 5-10 seconds if revs up high and idles perfectly. It almost seems like somthing is clogged if that makes sense. Are you talking about the sensor plate on top of the air box? How do I check the mixture? Thanks.

You need a set of gauges, our host sells a nice set.

http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_FULcis_pg18.htm#item63

[Gunter]

Originally Posted by jinos

It runs well when hot. It just has a real hardtime starting. It sputters and then dies out. So I tried pressing the accelerator and it still dies. But after the fifth try it sputters while holding the accelerator. After pressing the gas for 5-10 seconds if revs up high and idles perfectly. It almost seems like somthing is clogged if that makes sense. Are you talking about the sensor plate on top of the air box? How do I check the mixture? Thanks.

Pressing the accelerator is a good way to blow the airbox.

Check under the passenger seat for the ECU; it looks like a small radio-box with a relay on it.

'78-'79 SC's didn't have Lambda but '80-'83 have unless it's a Euro.

Sounds like you don't know much about CIS and may be better off letting a professional look at it instead of compounding your problems; there is just too much to consider for trouble-shooting.

Someone who knows these 3.0 with CIS can quickly see what's missing.

Do you have the Bentley? If not, get it and read.

[lioron]

check the grounding strap near the trannie. An old one may lose resistance when heated up and cause slow cranking and will not turn on.

[stlrj]

Originally Posted by jinos

I'm gettin so frustrated with this CIS crap. ahhhhhhhhh!!! I had a hot start issue so I worked from the bottom up and replaced the following: fuel pump, check valve, fuel filter, fuel accumulator, and fuel frequency valve. After all replacements my 911 74 with a 3.0 still won't start after running. It fires up with no problem when cold but won't after 10 minutes. What the h#$l is wrong with this? I'm so fed up with this right now. Any help is greatly appreciated.

Are you getting any residual pressure after 10 mins? In other words, can you feel any resistance at all when you push up on the senor plate?

[Gunter]

Originally Posted by lioron

check the grounding strap near the trannie. An old one may lose resistance when heated up and cause slow cranking and will not turn on.

The radio?

Yeah, and check the tire pressure.

[ruf-porsche]

Are you sure it's a fuel problem and not an ignition problem? When it doesn't start do you have a spark?

[Paulporsche]

Have you checked the control pressures, especially the warm cp, and the residual fuel pressure?

[jinos]

It's not the ignition for sure. New plugs, wires, distrib and all checked. Just replaced the warm up regulator and seems to be running better now, but will update if the problems occurs again. Thanks for all your help guys!