Spark/Vacuum Advance CTO Switch - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 06-14-2000, 03:03 AM
**DONOTDELETE**
Guest
 
Posts: n/a
Spark/Vacuum Advance CTO Switch

I replaced the Motorcraft 2100 carb on my '78 CJ-7/304, today. I'm very happy to say that it no longer leaks fuel, it idles much better, and it accelerates very smoothly while in Park or Neutral. It still stumbles, however, when accelerating while in gear. (Mostly when cold, less when hot.)

After hitting the books to try and solve this mystery, I discovered that the Spark CTO switch has been removed, and the vacuum advance is connected directly to ported vacuum 100% of the time. Would this set-up cause a "stumble" on acceleration, or is this an acceptable alternative set-up? All the smog crap has been removed, obviously, and I guess the CTO went with it.

Thanks,

Jim

I understand the meaning of the word "obsession" much more clearly now that I own a Jeep.

Sponsored Links
Advertisement
 
post #2 of (permalink) Old 06-14-2000, 06:43 AM
Keyboard Implanted
 
Join Date: Sep 1999
Location: Southeast Iowa
Posts: 6,394
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Spark/Vacuum Advance CTO Switch

[img]/wwwthreads_images/icons/tongue.gif[/img] We did not have that problem when our 304 was totally smogless and the distributor was connected direct. If I were you I would make sure that the accelerator pump in that carb is working.[img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
Quadra-Trac modified by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/tongue.gif[/img] transfer case team.
CJDave is offline  
post #3 of (permalink) Old 06-14-2000, 06:46 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: Spark/Vacuum Advance CTO Switch

Thanks for the info, CJDave. The accelerator pump is giving a good, clean shot, so I'm not sure what to do next. I've replaced all the vacuum hoses, reconnected the gas vapor cannister, backed off the choke, replaced the ignition control module-EGR-PCV, etc. The vacuum is pulling 17.5 or so, which is a vast improvement, but it still hesitates (just not as bad.) Guess I'll check the timing tomorrow.

Jim

Sponsored Links
Advertisement
 
post #4 of (permalink) Old 06-14-2000, 10:48 PM
Keyboard Implanted
 
Join Date: Sep 1999
Location: Southeast Iowa
Posts: 6,394
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Spark/Vacuum Advance CTO Switch

[img]/wwwthreads_images/icons/smile.gif[/img] Double check to see that the PCV valve is correct for that 304, and that the side outlet in the PCV valve goes to the "purge" port on the cannister. I have the complete smog layout if you need to check the hose routing.[img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
Quadra-Trac modified by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/tongue.gif[/img] transfer case team.
CJDave is offline  
post #5 of (permalink) Old 06-14-2000, 11:51 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: Spark/Vacuum Advance CTO Switch

I had the exact same problem with my 360. If you advance the timing it will run great but idle high. Dave knows all about my problem and my ineptness at solving it. I just want to replace the whole [email protected] thing. Hope you guys can get it figured out. Keep us posted.

Can you fix it?
I got a welder and a grinder. Heck yeah I can fix it.[img]/wwwthreads_images/icons/cool.gif[/img]
post #6 of (permalink) Old 06-15-2000, 08:35 AM
Keyboard Implanted
 
Join Date: Sep 1999
Location: Southeast Iowa
Posts: 6,394
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Spark/Vacuum Advance CTO Switch

[img]/wwwthreads_images/icons/tongue.gif[/img] I'm stubbornly clinging to my original idea that the PCV is incorrect. That is a critical item, and can easily be the wrong part. It would let in too much air and the mixture would be too lean, plus the idle would be abnormally high in order to compensate. The original part has a side outlet(See your Jeep booklet, page 4E-9)which goes to the "purge" port of the cannister.[img]/wwwthreads_images/icons/tongue.gif[/img]

CJDave
Quadra-Trac modified by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/tongue.gif[/img] transfer case team.
CJDave is offline  
post #7 of (permalink) Old 06-15-2000, 06:24 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: Spark/Vacuum Advance CTO Switch

I checked the timing, and it is 8 BTDC. TSM says 8 to 12 is acceptable. So I ended up pulling the plugs and cleaning them. There was a pretty good amount of carbon build-up on them. (Which I hope is due to the fact that this Jeep hasn't run much in the last year or so.) ...That seemed to help a bunch.

77cj-7, the biggest improvements came from replacing the carb, and replacing/rerouting all the vacuum lines. I used the vacuum diagrams that begin on page 4-63 of the Chilton's manual. (Huge improvement) What used to be a "stumble" and backfire during acceleration, decreased to a hesitation, and is now only a slight "bump." I could probably take care of it with some slight carb adjustments, but I'm almost afraid to dick with it.

I need to replace the exhaust system, which is leaking like a sieve. Then I'll try an ignition upgrade, which seems to be all the rage. (Motorcraft of course.)

CJDave, my PCV sits in the intake manifold with a "T" above it going to the back of the carb and to the canister.

Thanks for all the help,

Jim

Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome