CIS problem, Diaphram not lifting, will not idle
 

I searched and did not see anything describing this probelm.
Ok So my car is still at the body shop and they call last week and say, we can not get it to run right acts like it is on 3 cylinders.
I went up there and sure enough it will not idle run right or anything. I swapped all the plugs because it acted like it was flooded. Still no help.
So I had it started and lifted the diaphram next to the FD in the air box and back to life it comes running like a champ. Let go and it dies. My first assumption is there is a vacuum line broken, but do not know exactly where to look. The body shop is 50 miles from my house so I can not just try things to get it running.
Background,
Had the car for a year, starts up every time, idles up to 1200 when first cranked then settles in at 800 after a few seconds. Been pretty flawless except for not wanting to crank twice during the summer while it was hot, I think the fuel accumulator is bailing.

What do you think? Common problem. I am sure it has not been ran up to temp while it is in the shop.

Last question, I am really wanting to PMO's on it, is this repair super costly enough to go ahead and consider the PMO's?

Thanks
Phil

BIG VACUUM LEAK. Check for a loose hose. Or if you have a pop-off valve flip it and see if it reseat itself.

Or a body man put his foot on the throttle and blew your airbox.

That concerns me. It does a have a pop-off valve, it is seated correctly.

I am hoping it is a broken hose or loose hose. Again the car ran great going to the shop and they said it cranked and ran fine each time they moved it until Thursday of last week. It will not run properly at this point, no way I can drive it.

I'm guessing that there was a nice backfire and the popoff valve is now loose. Check not only that the flapper lid is closed, but that the valve itself is still seated and glued in. If it is loose, your car won't start. If it's tight, I'd check the airbox itself for leaks and then the hoses, etc. It does sound like a big vacuum leak is your problem.

PS: I've had backfires blow my popoff valve out of the airbox, while tuning with the airbox cover and filter off. Needless to say, the timing/tuning was a bit off at that point.

regards,

al

Ok thanks. Maybe the pop off is not completely sealed. It sucks because it is not in the garage. What are the odds the box blew even with the pop off?

Anything is possible, even a 27 year old Platinum Metallic 911 SC Targa without a popoff valve.

the screen in the warmup regulator, under the larger of the two screw in fittings can get clogged with debris and cause very high control pressure which will hold down the sensor plate. look for any screws that are out or 1/2 way out inside and around the airbox. air filter out to see this. evidence of a separated airbox.

not to cast any doubts... but... did you write down the mileage on the car... exactly... right before you handed over the keys at the body shop AND now, did you compare the two recordings from the odometer... did someone go for a HOT RIDE while the car was there for work & pop something???
Sorry to get you popssibly freakin' out but it happens more than you would think that the mgr goes for a test ride in a different car or off for lunch and one ot the 'young' techs wants to go try out the nice PORSCHE...
Thankfully the Porsche cars are built tough...
Bob

John,

Thanks for the feedback, I will have a look at that when I go up there again.
Bob, I don't think it was driven. It has been in pieces so that is not my concern. I have been concerned that it has only been cranked to move it. I had it for two weeks since Thanksgiving and it ran fine during those two weeks. The rest of the time they have had it, and really a couple weeks before then, so it has not been ran much.


I think I am going to rip my airbox off of my other 911 and take it up there as I troubleshoot. I would rather get it running as a tow bill is crazy from that far away.

Suprised no one has said ditch it for Webers though. I have been trying to talk myself into them for a year.

If it has started and ran reliably all this time, and then you take it to a body shop and suddenly it won't run worth a darn, then I am strongly suspecting something happened while it was at the body shop. Somebody unhooked something and failed to reconnect it properly. Somebody took it for a joy ride. Whatever. I would lean on the body shop folks, or just have it towed directly to a trusted mechanic for a diagnosis.

CIS is a very good and reliable system. That being said, if I ever need to replace an expensive component on my CIS system, Webers are going in.

Getting back to the hard start when hot last summer, more likely the check valve up by the fuel tank and pump whose purpose is to hold residual pressure when engine is shut down. If faulty the wait could be 20 minutes or more. I had one fail years ago and would take the air cleaner out lift the disc and start the car. Change the check valve not the accumulator.
Look for a big vacuum leak. If they have been back in the engine compartment for any reason then large vacuum hose is off or out of place. Is oil cap on tight?

Ok. I got the car home today. Tinkered with the diaphram while it was in the shop and got it to run. Now at idle it was running great under load it was bucking and backfiring.
When it was running at it's worst the relay under the seat and the relay for the fuel pump was clicking like crazy.
It does not appear to have a blown box, but I am not an expert. Again right now it idles fine but does not run properly under load. What do I check now?


Thanks
Phil

so is it a 79 or 80?, per your sig. an 80 would have an oxy sensor computer and a relay for it under the right seat. if that relay clicks, then replace it. if it doesn't turn on the computer, the system runs way lean. also check for a good fuse connection at the interior light fuse, which powers the relay. thatr relay and the fuel pump relay are inter-connected, through the sensor plate contact. unplug the green plug at the back of the sensor plate and see if they stop clicking.

Thanks a Ton John!!!
It is the 80. You may be onto something. I am not at home, BUT I do remember seeing the fuse missing for the interior lights when I was picking it up. It looks like they blew my power window fuse and swapped the interior light fuse for it.

I can assure you this car was not 'joy ridden' while at the shop, it was only moved from one bay to another a few times a week. I do know that the distributor was wired wrong as the cap was not seated in the proper place and so none of the wires were in the 'right' place. Have you found anything with that yet Phil?

A CIS-Lamda 911 will run like crap with no power to the O2 system. Like John said, the lamda box under the seat gets power from the dome light fuse. If they pulled it, that is most likely it.

The cap was not wired incorrectly. Firing order was correct. It was not seated correctly,(meaning the tab for the notch was 180 off or facing the rear of the car), which I corrected the first time I went up there. When I did the heater backdate, I must have put the cap on wrong, but two things that was 7 months ago and timing had been set in october.
I also have not made any claims that the car was joy ridden.
Again, I am not at home tonight, but I will check those fuses when I get home.

Ok got home this morning. And John you are a genius, the fuse was missing for the interior light. My guess is either the buzzer was bothering them or they used it after the power windows fuse blew. When the switches were taken out (not by me) they were not wired correctly so it must have blown the fuse. I corrected that (was cold driving home last night).
Thanks to all the Pelicans who helped out.