Diagnosing slow chugging during first 10 seconds of cold startup

jwakil · jwakil's Garage

My my 83SC with 1977 3.O CIS engine has a peculiar problem on cold start-ups in the morning. The first time I turn the key, it will slowly chug and chug at <400RPM, giving out a few pops or backfires. Eight times out of ten the RPMs will rise as they should after ~10 seconds, and the other few times the engine will die out but always start right up on the second key turn. Would this indicate a cold start switch, Auxilary Air Regulator, or other problem? It doesn't have this problem when engine is warm.

Sean A · Sean A's Garage

I am also curious what this "chugging" is about. I have a 2.7 CIS, with a hand throttle. With the lever all the way up, it revs to 3000. When i push the lever down to decrease the idle, it drops to below 1k rpm and chugs. Pops, Backfires, feels like its going to stall, then after 5 seconds or so returns back to regular high idle.

Im thinking the engine could just be running a little lean for the conditions or something similar.

stlrj · 07-06-2010, 01:24 PM

Leaking injectors?

Scott R · Scott R's Garage

You need to check your cold control pressure, it sounds like it's off.

Steve@Rennsport · 07-06-2010, 03:35 PM

Scott is right: you need to get the CIS fuel pressure guages and check cold control and system pressures to see what is going on.

jwakil · jwakil's Garage

I had the pressures checked some time back and they were fine. I would be surprised if anything has changed since then. Actually, I had thought about getting a hand throttle to solve the problem, but sounds like from Sean that's not the answer, and his would not be a cold control presser problem, would it?

Scott R · Scott R's Garage

Hand throttle is not the answer, you're just masking a problem, and to be honest doing things like that will probably result in a blown airbox.

The CSV runs while cranking if the temperature switch is closed. After that you're on to control pressure. If thats out, or the basic mixture is wrong then you get the symptoms you describe.

A working CIS system needs about a crank and half from stone cold to start. It idles up a bit if the AAV is open, and then down when the AAV and WUR have been warmed by the elements and engine temperature. The system can be driven right away and doesn't chug or lope, it just runs nice and smooth.

T77911S · 07-07-2010, 06:47 AM

+1 with above. dont mask the problem by... , well i wont go there.

if it is turning over slow, it could be a bad battery, bad connections, bad solenoid or bad starter.

i would first clean ALL the major connections, dont forget the tranny to body, and clean the battery cable on the starter too.

then i would have the battery and charging system checked. places like advance will do it for free.

if that is all good, i would look into the solenoid. the contacts get burned and pitted on cause a big voltage drop to the starter motor.

ossiblue · 07-07-2010, 06:59 AM

Quote:

Originally Posted by jwakil

I had the pressures checked some time back and they were fine. I would be surprised if anything has changed since then. Actually, I had thought about getting a hand throttle to solve the problem, but sounds like from Sean that's not the answer, and his would not be a cold control presser problem, would it?

Follow the above mentioned advice and begin with pressure checks. Don't be misled into thinking that once pressures are set that they will remain in spec--warm pressures, maybe, but cold pressures are easily subject to change especially with an older wur. One step at a time with CIS. Take it slow and methodical and take nothing for granted. Begin with the easy/obvious (pressures) and go from there. You'll save yourself time, money, and frustration.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Scott R

Hand throttle is not the answer, you're just masking a problem, and to be honest doing things like that will probably result in a blown airbox.

The CSV runs while cranking if the temperature switch is closed. After that you're on to control pressure. If thats out, or the basic mixture is wrong then you get the symptoms you describe.

A working CIS system needs about a crank and half from stone cold to start. It idles up a bit if the AAV is open, and then down when the AAV and WUR have been warmed by the elements and engine temperature. The system can be driven right away and doesn't chug or lope, it just runs nice and smooth.

Scott,

My guess it is a typo about AAV. Maybe you meant auxiliary air regulator (AAR)? In some reference books/manuals they interchanged the names of auxiliary air regulator and auxiliary air valve. However, in this forum we know the difference between AAR and AAV. Hope this helps clear some confusion with the other readers.

Tony