CIS Starting Problem

[k_dub]

I have been reading for two days about the joys of the CIS system and all of the various problems out there surrounding cold start. I have a pretty good list from other posts on things to check, but I wanted to post my problem here first because my problem does seem to quite line up with what I've read.

The car is a 1980SC with a '75 2.7 in it (interesting story of my start into 911s) it has been starting great all summer on the first crank, sometimes with a little throttle to help (the car didn't move over the old throttle lever that I think probably should've been done) but never really had a problem starting it.

I'm in Ontario, Canada so over the last week the temp dropped from staying around 60-65ºF to 40-45ºF. The car still started great in the garage in the mornings, but I took the car to a friend over the weekend and left it out overnight and when I cranked it, the engine would catch on the first crank, rev to about 1200-1500 (like a normal start before it drops to idle) and then quits. It does this everytime until I get it to start and keep running at which point it seems to run happily for about 30 sec and die regardless of what RPM I manage to hold it at. Once it runs for a little while the problem goes away and can shut it off and it will start first try again. I eventually got it home and back into the garage and the temp dropped even more the next night, but the following morning it started first crank in the garage again.

The last interesting bit of this story was that I took it out again yesterday and it ran fine for the 2.5 hour cruise to a friend's cottage for the day. Temp stayed about 65ish, but when I went to start it after about an hour after the drive in (motor was still warm to the touch) the problem happened again, just not for as long)

Oh yeah, one other thing I tried, I decided to hold the starter in the "start" position after it would catch and it seemed to run fine while the starter was still engaged, even could rev a little (bad for the starter I know but I wanted to see what happened) but died with the key back in "run"

Sorry for the book on the problem, but it seems really strange to me. Any thoughts? The biggest thing confusing me right now is why it seems to only happen when the car is outside and not in the garage, the temp isn't that different.

Thanks

[ossiblue]

I see several possible areas of difficulty, not all necessarily related to each other, so I'll just post my thoughts so you and others can have a starting point.

I'm going to assume from your post that the 75 CIS did not receive the 1980 warm up system. In a stock 75 set up, the hand lever not only opens the throttle a bit, it also closes the micro-switch on the throttle body which allows the cold start injector to work when the starter is cranked. I assume you are activating the injector when you use the foot pedal during starting--that will work--but unless you do that each time, the cold start injector will not always work and you will get intermittent results. Your problem doesn't appear to be initial firing but rather continued running so this issue may be moot. Just be aware that as the weather gets colder, your car does not have an adequate warm up system installed, and you may run into difficulty until the car is warmed up.

Moving on.
I'm in Ontario, Canada so over the last week the temp dropped from staying around 60-65ºF to 40-45ºF. The car still started great in the garage in the mornings, but I took the car to a friend over the weekend and left it out overnight and when I cranked it, the engine would catch on the first crank, rev to about 1200-1500 (like a normal start before it drops to idle) and then quits. It does this everytime until I get it to start and keep running at which point it seems to run happily for about 30 sec and die regardless of what RPM I manage to hold it at. Once it runs for a little while the problem goes away and can shut it off and it will start first try again. I eventually got it home and back into the garage and the temp dropped even more the next night, but the following morning it started first crank in the garage again.

This sounds like a typical overly lean condition, typical when cold temps hit. The brief running is from the fuel from the cold start injector. The immediate dying is from lack of adequate fuel through the engine's injectors--most likely from too high fuel cold pressure but also possibly from air leaks. First step, check your pressures with a gauge set. Too high of cold pressure, or air leaks, will cause the cold running engine to die--or backfire--regardless of the RPM you try to maintain, until it warms up. Remember, you don't have the automatic warm up devices of the 80 model to ease you through the warming cycle and you don't have the throttle lever to keep the throttle open until warm either. All in all, I strongly suspect your WUR is out of spec for cold pressure. Do the pressure check and report back.

BTW, the incident at your friend's cottage is not inconsistent with out of whack cold pressure. An engine warm to the touch is not necessarily a "warm" engine. The fuel pressure still could be too high for the ambient temperature.

If your WUR is in spec, another possibility is air leaks and, following that, fuel pump delivery problems. However, I suggest you do the easiest testing first(fuel pressures), eliminate that as a possibility, and move on from there. Let us know your results.

[k_dub]

Thanks for the starting point. I will start digging into this, I don't have a gauge set at the moment but I will be getting one this week. I just wanted to make sure that I wasn't dealing with something different as sputtering and backfiring wasn't something I was having a problem with.

Once I have pressures I will report back.

You brought up an interesting point though, can the '80 warm up system be worked onto this?

[k_dub]

Well I ordered a set of gauges from a local place but unfortunately (even after asking) the kit didn't come with proper adapters for the CIS. So I kept reading and came across calling911's tuning CIS without gauges post and tried it and low and behold I got the car to start normally again.

I'm still going to get a set of gauges to check what my pressures are like, I was hoping to find somewhere closer than pelican (and potentially on this side of the border) but no luck yet.

Thanks for the help.

[Groesbeck Hurricane]

Did you check the rubber hoses to ensure they are in good condition and not leaking? Check each hose one at a time.