Hot and cold start - I've read too many posts and am more confused!

[laszloten]

Hello all,

I have been looking and reading for too long and its confusing me even more!

I have an 83 SC that has an issue with cold and hot start.

The cold start: If it sits for a couple days/less than a week, it cranks for at least 5-10 cranks before it starts, up to 2k, back down to 2-300 and then it oscillates for a minute between 7-1200. After that it runs with no hesitation or backfire.

If it sits for more than a week, it starts on first crank, up to 2k, back down to back down to 2-300 and then it oscillates for a minute between 7-1200. After that it runs with no hesitation or backfire.

The warm start: from 1 minute to 20 minutes it starts first crank and sits at 900rpm.

If it sits for more, it cranks for at least 15-20 times before it starts, oscillates and then when I move it sits back to normal idle.

I have had the fortunate luck to receive a brand new check valve and accumulator at no expense with no change in symptoms, if anything worse (more cranks).

Someone lead me in the right direction please.

Thanks

[ossiblue]

The oscillating indicates an overly rich mixture and in each of your situations, save one, you are in a technically cold start situation with regard to the thermal switches in your system (and the one normal situation is when the car is fully warm.) I have no experience with the lambda system on your year car, but that's where my suspecisions point. You have an ECU under the passenger seat that controls your cold start system in addition to your WUR. Someone with knowledge of this system and the symptoms of a failure will chime in soon, I'm sure, but this post may head you in the right direction.

[gazzerr]

laszloten, here is the definitive thread for solving CIS issues. I would start with this:

CIS Troubleshooting for Dummies

[boyt911sc]

Is your car a USA/CAN or Euro/ RoW model? Inspect and identify the number (ID) on top of the WUR. Keep us posted.

Tony

[Bob Kontak]

Originally Posted by boyt911sc

Is your car a USA/CAN or Euro/ RoW model? Inspect and identify the number (ID) on top of the WUR. Keep us posted.

Do this

Also, where are you geographically? You may have friends close by.

[tirwin]

Ok, so you read some of the posts on the topic. That's good for starters.

Check out the troubleshooting table that Jim Williams did:

911 CIS Primer - Troubleshooting

Ok, you know you have hard cold starts. There's a starting point for causes.

Now take each one on the list and build a plan to address each one. There is a better than 50/50 chance you have more than one issue. Example: engine has unmetered air and someone riches the mixture to compensate. What happens when you fix the false air problem? Now the mixture is too rich.

It's good to gather data. Check fuel pressures, dwell and timing to start. Then execute the test plan. 3 major areas: fuel, air and spark?