I posted my odd starting problem a couple of weeks ago, to very little response here, though I got some good suggestions elsewhere...

*cough*MAZSPEED*cough*

Anyhow, just to bring everyone here up to speed, my car had developed an adversion to starting and running in cold weather. Typically the car would start and run decently enough initially but at a fairly early point in the warmup cycle, it would just die. Attempts to keep it running by giving it more throttle or choke only killed it quicker. Once dead, the car refused to restart until I turned the key off and waited. This occurred a random number of times until the car warmed up enough for the problem to fade.

Troubleshooting this problem has been an experience to say the least. My battery has and holds a good charge, my fuel filter is new, as is my fuel pump. All ignition components were replaced when I installed my DLIDFIS system this summer, so no worries there. My carb has been rebuilt and seems to be working fine, albeit slightly on the rich side. Nothing I did seemed to make any difference in this problem. Initially I thought that if I installed my carb stove and heat riser tube, I could allieviate the problem, but that didn't work, though I kept it on for faster startup and warmup cycles, plus it doubles as a heat shield for my header.

Finally it struck me. As an afterthought in the first thread, I mentioned some gurgling in the fuel tank after the car died and I turned off the key, killing the pump. Because my fuel filter was fine, I dismissed this gurgling as normal and paid it no heed. It turns out that if I remove my gas cap, my car does not die during warmup, and the gas tank does not gurgle. My vapor canister is not plugged, nor is the check valve on the fuel return line, but unless I leave my gas cap loose, my car will not run when it's cold. When the car is warmed, it runs fine with or without the gas cap installed.

Now, what the heck is going on here?

 

Good question!
Sorry I can't make sense of it either. I'd probably start by removing the fuel tank and checking the internal lines. Or just leave cap off but it may come back to haunt you later if you do that.
Good Luck

 

Well it's obvious that you have something plugged related to your fuel tank. Bout all you can do is pop er down and see whats plugged. Might as well replace all the fuel lines while it's down seen as how your going to end up replacing something.

 

guys its the gascap ! the caps supposed to allow amospheric pressure into the tank to replace the volume of the fuel consumed , during warm up is without a doubt tthe highest fuel consumption, before emissions and charcoal canisters the caps vented both ways allowing raw hydrocarbons to escape into the atmosphere , these evaporative light ends venting allowed the gas to sour cause all the heavy **** was left behind, now the caps only work one way , they seal against positive tank pressure and the tankvent tube
routes the now fuel heavy vapor to the charcoal canister, where its eventualy burnt by the engine during the purge cycle, so long storie short suck from the tank side , but no blow signals good cap, i think you have no suck and no blow, you pour guy get you a red head!

 

Ok Trevor, that actually makes little sense but I got lost at the long storie short part. I guess you made the story too short. So..... he should do what now? To test for a clogged charcoal canister perhaps he could pull the lines off of it so the vapors vent to atmosphere for a while?

 

I think he's saying "replace the gas cap" ... I think ... in dankus-speak.

 

thats what I heard. Probably not a bad idea just as some normal maintanence anyway, its cheap.

 

There can't be anything clogged in the fuel lines, because this problem is temperature sensitive. If I had a heated garage, I would never have this problem as it only occurs when the mercury drops down to the minus 15 to 20 Celsuis mark. My gas cap is new and I don't think my vapor canister is clogged. Calling it a canister is somewhat of a misnomer though, on the SA, the charcoal is integrated into the lid of the air cleaner. It's still freaking cold outside, so I guess I'll put the gas cap on properly and disconnect the vapor line going to the air cleaner and see how it goes...

 

alrite ., i went back to the service manuel and studied how the atmosphere vents to the taank, and from what i under stand its the check and cut valve located back by the gas tank, this allows your incoming air to replace fuel consumed, and judging by your discription of problem you have either moisture build up thats freezing, or the valve actually sticks in cold weather, hope that helps. short storie this time!

 

as a diagnostic check i would se a trouble lite with a standard incandescent bulb under the car undr the valve , if it starts in the morning you know it is your problem