83 SC "Cold" Start

DDD · 07-08-2004, 08:50 PM

Have looked through many cold start threads, but can't find this exact situation. My car runs fine. Starts immediately if I have driven it for a few minutes (maybe even a few seconds). But, if the car has been sitting for more than a few hours, even on a warm day (hence I don't know if you technically call this a "cold" start), it does the following upon turning the key: Immediately pops right off and sort of starts, runs about half a second, and then stalls, as if it is starved for fuel. Then, if I try to start it, it just cranks and cranks. I have to let it "rest" for at least 3-5 mins, then try again, and if I hit the gas right EXACTLY at the moment it immediately pops off, I can keep it running. Backfires a few times, runs rough, then smooths right out after 30 seconds or so. Car has no related mods, other than a popoff valve I put in maybe 10 years ago.

One other comment: Car just started doing this this "season", sometime around the time I adjusted the valves for the first time in a few years. I'm thinking either I pulled some sort of vac line loose, or I've got a fuel pump starting to die on me.

Appreciate anyone's insight. --DDD

epbrown · 07-09-2004, 06:32 AM

This sounds like the fuel pump accumulator or check valve to me. These maintain fuel pressure in the lines when the car isn't running. If these are bad, the system loses pressure (bad accumulator) or the gas drains back to the tank (check valve). When you try to start the car, it sputters and dies from lack of fuel.

When cold, the cold start injector puts in more fuel to get you running, but if the car is above a certain temperature ithe CSJ doesn't work. The symptoms are masked during colder temps, but if you're in a really warm area where the engine stays warm enough not to call the CSJ into action for longer periods, the problem becomes evident.

When you wait a few minutes, you give the fuel pump more time to bring the system up to pressure and start/run normally.

Emanuel

sammyg2 · 07-09-2004, 08:12 AM

If it happens when the engine is cold, it shouldn't have anything to do with vapor lock from an accumulator or check valve.

The popping and struggling you describe sould like a typical lean run condition.
It could be a few things:
1) a vacuum leak from a hose, the pop off valve, where-ever. (very possible)
2) The WUR not functioning correctly (also very possible)
3) The thermotime switch is not functioning properly which is not turning on the cold start injector (my bet is on this, check the wiring to it)
4) The fuel pump relay may be lose and working intermitantly (long shot)

If the fuel pump was weak it would be most noticeable during extended full throttle conditions, prolly not at idle but it would be worth checking all the fuel pressure settings.

Paulporsche · 07-09-2004, 08:49 AM

Even on a warm day, if your car has been sitting for a few hours, this is considered a cold start.

I think sammyg2 is on the right track. Check your cold control pressures. I'm leaning toward your WUR, but try his other items too.

You might try enrichening your mixture by 1/8 turn. Don't forget to turn your idle back up at the same time.

Let us know how you make out.

Paul

DDD · 07-12-2004, 07:04 AM

Just wanted to say thanks for so many quick replies. Sammy: After your note, I went a checked a few things. Bottom line: The problem seems to be fixed, and I don't know why. I checked the popoff valve - the seal looked good and the valve itself was tight. Not knowing how to check the thermotime switch itself (I assume there is a voltage test described in a manual somewhere?) I pulled one of the two wires (the black one) off the switch (I liked that idea, partly because Sammy suggested it as the most likely culprit, but mostly because it sounded reasonable and it is also easy to get to), and the car started right up. Since then, I have reattached the wire, and car still is starting right up. I honestly don't buy this, but maybe I just had a bad connection there? Life is never that easy!

Anyway, thanks again, and let me know if the above causes you to have any other thoughts.
--DDD

sammyg2 · 07-12-2004, 10:11 AM

Great to hear your problem has gone away. Hopefully it stays away.

Sometimes the pop off valves don't seal all the way and need to be jiggled a bit to re-seat.
If it was just a bad connection you win the prize for the easiest fix for a difficult diagnosis

Paulporsche · 07-12-2004, 12:37 PM

Congrats.

Always check the easy, simple and cheap things first.

DDD · 07-12-2004, 02:26 PM

Thanks again for your thoughts. I disconnected the thermotime switch and jiggled the popoff valve during the same "session", so I don't know which did it. That is good info on the popoff valve not always seating correctly. Given how unlikely it is that I had a bad connection on the switch, I am guessing that the popoff was the problem. I'll never know, unless it starts doing it again.