Cold Start Issue - Video

mca · 08-12-2007, 11:38 AM

Cold Start Video:
http://www.reactionplus.com/pcar/coldstart.html
I do not touch the gas pedal prior to starting nor do I touch it at all in the video until the very end after it has started idling ok.

I know that the chances are slim (since a video isn't much to go on), but I am hoping that the video may shed some light on my cold start problem before I begin my troubleshooting process. Maybe you guys will see something very obvious.

BTW, I could keep it running on the first try if I wanted to by giving a little gas. But I need to start thinking about solving the problem instead of finding my way around it.

Warm Start Video:
http://www.reactionplus.com/pcar/warmstart.html
This video shows that the warm start is completely fine.

As always, any help is appreciated. I don't currently have any CIS tools other than the mixture adjustment tool. No fuel pressure testers, etc.

I do have a new fuel pump and fuel filter. But the cold start problem did not arise as a result of installing these items.

Cheers,
Craig

safe · safe's Garage

If you use a little throttle when starting cold and hold it a little until the engine stabilize, does that work?

mca · 08-12-2007, 12:11 PM

Quote:

Originally Posted by safe

If you use a little throttle when starting cold and hold it a little until the engine stabilize, does that work?

Yep ... I can use the throttle for 10 seconds or so and the engine will settle into a nice idle. But if I let the RPMs drop below 1000, the throttle won't help and the RPMs continue to drop ... then the engine barely recovers but was close to quitting.

fireant911 · 08-12-2007, 12:45 PM

mca,
There could be a variety of things causing this... when I purchased my 81SC it did the exact same thing - cold starts would always run rough and the engine would die once / warm or hot starts were always fine. One day, while checking the the operation of the auxiliary air value, I saw that the something was blocking the ID of the hose. I removed a flat round blank of metal (basically a centerless washer) and reinstalled the hose. The problem disappeared at that point. The PO had sent this car to a very reputable shop in Birmingham to correct this problem but they could never find the reason for that behavior.

mca · 08-12-2007, 01:53 PM

Quote:

Originally Posted by fireant911

mca,
There could be a variety of things causing this... when I purchased my 81SC it did the exact same thing - cold starts would always run rough and the engine would die once / warm or hot starts were always fine. One day, while checking the the operation of the auxiliary air value, I saw that the something was blocking the ID of the hose. I removed a flat round blank of metal (basically a centerless washer) and reinstalled the hose. The problem disappeared at that point. The PO had sent this car to a very reputable shop in Birmingham to correct this problem but they could never find the reason for that behavior.

Thanks for the info. Man, this could be a huge help.

Paulporsche · 03:25 PM

Well, it seems like it might be what most cold start problems appear to be w/ CIS cars: a too high cold control pressure, resulting in a too lean condition @ start. If you check your ccp w/ a gauge, then you can tell if you are in spec and need to adjust or replace your WUR.

It's also possible your mixture is set too lean or you have a vacuum leak that closes up when warm, but, if you search this, the out of spec WUR seems to be the most likely.

BTW it's hard to tell since I'm listening on my poor lapop speakers, but I'm not hearing a "chain rattling in a trashcan" noise @ or just off idle am I?

mca · 08-13-2007, 05:30 AM

Quote:

Originally Posted by Paulporsche

BTW it's hard to tell since I'm listening on my poor lapop speakers, but I'm not hearing a "chain rattling in a trashcan" noise @ or just off idle am I?

Are you hearing that on both videos? I don't think it is making a "chain rattling in a trashcan" noise but I will listen more closely ... my ears are not yet trained to pick up on particular noises.

What would be the cause of the noise?

Paulporsche · 08-13-2007, 01:55 PM

mca,

I just relistened on my desktop which has much better speakers, and I don't think I hear that dreaded sound, which is the sound of failing chain tensioner$!

mca · 08-13-2007, 03:13 PM

I thought you might be alluding to chain tensioners. Fortunately I installed a the carrera tensioner 2 years ago ... hope it lasts a while.

stlrj · 08-13-2007, 04:28 PM

A new warm up regulator should fix it or have the existing one adjusted to enrich the cold start mixture.

Cheers,

Joe

Paulporsche · 08-13-2007, 06:15 PM

You can try richening your mixture a little, say 1 or 2 1/16 turn twists clockwise and see if that cures it. The best way to tell is w/ the gauges, but this may just do it. Try that and let us know what happens.

safe · safe's Garage

Yes, try to richening the mixture a bit and see if it helps. A long, but not to long, 3 mm allen wrench is needed, turn clockwise to richening . Take care so you don't "get lost" from your original setting.

Then go somewhere to get it properly adjusted to just under 3%, if that i legal in your area.

A full check for vacuum leaks might also be in order on any 25 year old engine.

K9Torro · 08-14-2007, 02:34 AM

My 79 did the exact same thing, replaced the WUR and have not had a single problem since,

Todd

safe · safe's Garage

Quote:

Originally Posted by K9Torro

My 79 did the exact same thing, replaced the WUR and have not had a single problem since,

Todd

That doesn't guarantee that this is the problem for MCA, even if its probable.
I'm a firm believer in finding the error before changing expensive parts (the WUR fall into that category) at near random.

A fuel pressure gauge can be bought/build/borrowed to check the cold fuel pressure. There's probably a bunch of Pelicans in your area that help you with a pressure gauge.
The workshop manual with the procedure usually floats around the Internet.

If the pressure is outside the specification, the WUR can be replaced or adjusted.

emac · emac's Garage

Paul

I just might be wrong, but isn't 1 to 2 turns rich wayyyyyy too much?

Ron.G · 08-14-2007, 05:25 AM

Show is.

930LDR · 08-14-2007, 06:04 AM

Cold start mixture is my guess. If your warm starts are good you probably don't want to mess with the mixture screw at the fuel head for fear of messing your warm start condition up.

Get your WUR modified so that you can adjust your cold start pressure. I had Brian Leask do mine for the 930 and it came out great (many have done it themselves but I lacked a few of the bench tools). I had been fighting an overly lean condition on boost and once I got the car to run rich enough during enrichment it would run very similarly to yours on cold starts. A bit of tinkering in the mornings and I got it dialed in.

Once the WUR is modified, the cold start adjustments are really easy and can be performed with the WUR installed. Just a small wrench is all you really need.

930LDR · 08-14-2007, 06:06 AM

Quote:

Originally Posted by emac

Paul

I just might be wrong, but isn't 1 to 2 turns rich wayyyyyy too much?

As I read the post I think that Paul intended for the adjustment to be between 1/16 and 2/16s of a turn.

safe · safe's Garage

Quote:

Originally Posted by emac

Paul

I just might be wrong, but isn't 1 to 2 turns rich wayyyyyy too much?

Paul wrote: " 1 or 2 1/16 turn twists clockwise", not 1 or 2 turns.

stlrj · 08-14-2007, 06:13 AM

The mixture adjustment is for a warm engine. Since you have no issues warm, I would leave that alone unless you want to create other problems and concentrate on your cold start mixture (warm up regulator).

Cheers,

Joe