930 engine CIS problem, please help
 

Hello I have a car with a 930 engine and yesterday the car stopped. i know that there is a problem with the injection system, but not sure what is wrong.

the problem started after i had a hard acceleration in first gear, when i was going to put it in second gear the engine starts to run uneven and suddenly stops.

beforee it stops i look on my wide band air fuel ratio digital gauge and i can see that the engine doesn't get any or not enough fuel. I try to start the car but it only splutter a bit and wont run. i get the car into my garage and check the fuel pumps, they get power when turn the key.

i then detach the fuel line that goes into the CIS (after the filter) and put the hose in a bucket, try to turn the key and it comes plenty of fuel.

I then attach the hose again and try to start the car, the car starts but the engine runs very uneven and it wont idle. with the gas pedal carefully pressed i manage to get the engine run at 2000 RPM. after 30 second the car stops and wont start. I can see on the fuel ratio that i doesn't get enough fuel and the AFR peaks up 22 and then goes back to 14, this happens some times before it goes up to 22 and engine stops.

I wait some minutes engine starts and the same happens.

Please does anyone have any idea what can be wrong, and what should i check first?

Kjell

Spark.

Spark issues shouldn't cause leaning like that. You need to check fuel flow at the injectors. You can pull them, put them into glasses, turn on the ignition, and push up on the air flow meter and you should see, after say 30 seconds, an equal amount of fuel in each glass. I'm not sure of the spec'd amount of fuel that should flow from each injector in a given time. In the SC it's easy to get to the fuel plunger (pushing up on the air flow meter) but haven't tried this in the 930.

Check all the fuses. my car was dying and I had to really rev it to go home. The cra would die at every slow down or light unless I revved the crap out of it. I drove home playing w/ diff. geras and the clutch just to make it. I checked and one of the bullet fuses was out in the rear of the car. Called my mechanic and he said that one shouldn't be the problem..put the fuse in and 6 months later no problems.

These CIS cars do some strange thing sometimes ;(

What about the CDI box when mine was going bad a few years ago I had some weird issues before it died??

Just a fyi... on 930 CIS the airflow plate goes the opposite dirction from the 911SC.
you gently push it down on a 930 to mimic airflow and send fuel to the injectors.

What happens on an AFR meter when fuel gets injected to a cylinder but is never burnt?

Did you check your O-rings and turbo up-pipe? They could have blown out causing a huge ail leak during your hard 1st gear run.

Cool, thanks for the info.

As you surely suspect, you would see a rich condition.

Check spark, then go for air leak
 

First, no spark will definitely show lean on wide-range O2 (Oxygen goes in, and comes back out again --> lean O2)

Pull plug wire, attach plug, ground at threads and look for nice blue spark.

If none, check ignition.

If there, look for air leak. Air leaks downstream of the flapper door means that air is getting into the engine that has not been "accounted for" ---> lean condition. Check that big rubber elbow that comes off the airflow meter. I have had that come off and cause a similar symptom.:mad:

+1 to Brian's comment, I vote for IC o-ring. This is exactly what my car did when I popped the o-ring last week.

Thanks, this was my understanding.

Shame the car doesn't run. If it did and when it got on boost it went rich then it would very likely be an air leak.

I think Brian is right as it likely got blown out when on boost and you lifted off the gas.

Thanks for the help.

I do not have a original inter-cooling system, but a water-cooled system, so RarlyL8 you are correct.

Because of my hard 1. gear run the turbo pressure made the silicon hose on the inter-cooler inlet to pop of. I discovered this when i started to dismount the pipes.

It was very strange that the engine will not run at all if it doesn't get air from the the turbo, not even on idle running. So the conclusion is that the engine did get too much fuel and when the fuel amount is way too high the Inovate LC-1 wide band AFR gauge does give a wrong indication, so it looks like there is not enough fuel but in reality the mix is pig rich.

i connected the silicon hose and everything worked fine.

http://forums.pelicanparts.com/uploa...1214859999.jpg

and here you can see why i have a watercooled system

http://forums.pelicanparts.com/uploa...1214860521.jpg

http://forums.pelicanparts.com/uploa...1214860732.jpg


thanks for the help

Kjell

Thats the first time I've seen an air pump filter attached to the inlet side of the cold start aux air slide valve or whatever you want to call it.
Thats unmetered intake air during cold start and warm up with it like that.

Maybe your car is so rich it works anyway.

I didn't know how else to solve it, but yes it's very rich during varm up. do you have any suggestion?

Kjell

Very cool.....
More pictures please! Are those oil lines on the driver side?

Steve, no they are self made 1" aluminum piping for cooled water to the inter cooler. I made the piping in aluminum because it heat transferee and weight are is the best on this material.

You can see some more here.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/371584-watercooled-intercooler-system-aircooled-911-a.html

Kjell

I was wondering WTH that was in chillers other thread.

I too would have thought that would mess up the idle mixture and starting etc etc.

Because air got in past the metering unit the mixture was in fact too lean, as indicated by the LM-1.

If un-metered air enters the engine the CIS will not add enough fuel to the engine.

Having the air come through the metering unit will make it run even richer still.

I see another problem though... When on boost, air will come out of the electric idle valve (the thing with the sliding disc in).
This is a waste of boosted air and will also make the engine run richer on boost.
The stock factory IC had a connection for it on the cooled side of the IC.

I was thinking to conect the Warm up regulator inlet after the turbo, but before the inter-cooler. This because there are limited possibilities after the inter-cooler.

So you mean that when the car is on boost the air will leak out through the warm up regulator?

Does anyone have a picture that shows how the original piping and hose setup was on the 930?

thank you for your help

Kjell R