74 CJ5 258 black exhaust problem - JeepForum.com
 5Likes
  • 1 Post By oldschool74cj5
  • 1 Post By BagusJeep
  • 1 Post By pedal2themetai
  • 1 Post By oldschool74cj5
  • 1 Post By Fourtrail
 
LinkBack Thread Tools
post #1 of 11 Old 05-21-2020, 08:51 PM Thread Starter
drewwilson
Registered User
 
drewwilson's Avatar
1974 CJ5 
 
Join Date: Jul 2015
Location: OKC
Posts: 27
74 CJ5 258 black exhaust problem

I have the original 258 and Carter YF 6432S carb in the CJ. Had a problem with black exhaust and immediately thought carb needs to be serviced (bought it 2 weeks ago, has been sitting/minimal use for over 5 years). Got it all cleaned out and inspected, new gaskets and float adjustment. Reinstalled today and...black smoke on start-up and idle still.

Pulled the spark plugs to inspect, all 6 had bad carbon build-up. Thought that may have been from before the carb service so I cleaned them all up, checked gaps and reinstalled. Ran the engine for about 2 minutes. Still black smoke. Pulled the plugs and they were back to black. All plugs looked the same so I don't suspect any valve seal problems.

The engine starts with no issues. Idle is a little rough (putts somewhat) but not bad -- never stalls. When I get the RPMs up to 2500-3000 the exhaust runs clean. When I let off the gas the smoke immediately returns. It has plenty of power. Timing is good. No misses.

I think it may be running rich and since I only see smoke when at idle and up to 2500 so I am going to adjust the idle mixture. The carb guy said he adjusted the float to within specs (1.38).

I am going to be putting in new points, plugs, wires. I don't want to do that until I can get the exhaust situation figured out.

Any ideas on what else it may be? Thanks.

drewwilson is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 05-21-2020, 09:33 PM
oldschool74cj5
Registered User
 
Join Date: Jan 2017
Posts: 503
hello

if you have points in the 74 you have to do it all kinda at once. put new points, make sure the gap and dwell are set properly. and setup the carb. it all works togethor.

when you rebuilt the carb did you remember the low idle jet. or make sure its tight and not leaking fuel around it. also is your choke being opened enough when it starts.

once way to check for to rich is when you give the engine a small vacuum leak and see what the rpm does. it might go up just a little but should drop and run rough. i like using a vacuum gauge for setting the mixture at idle. you want to get the highest vacuum with the mixture screw.

oldschool
drewwilson likes this.
oldschool74cj5 is offline  
post #3 of 11 Old 05-22-2020, 03:16 AM
BagusJeep
Web Wheeler
 
BagusJeep's Avatar
1981 CJ7 
 
Join Date: Jul 2009
Location: Bali
Posts: 7,524
Sure it is excess fuel? You will get strong fuel smell from the exhaust and the smoke will quickly dissipate.

yf has a metering rod which needs to be set up right. Have you got a smooth idle whilst adjusting the idle air screw? How many turns out does it start to stumble?
drewwilson likes this.

BagusJeep lives in Bali.

1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
BagusJeep is offline  
 
post #4 of 11 Old 05-22-2020, 07:05 AM
pedal2themetai
Registered User
1956 CJ5 
 
Join Date: Apr 2015
Location: Boise
Posts: 1,559
HI. There are two settings for the float.. Level and Drop.. if the Drop is set to high it well let to much fuel into the bowl and cause flooding (black smoke).
Run the motor shut it off and look down the carb. watch for smoke or fuel dripping out into the carb.. any smoke or vapor is raw fuel. The causes for that are bad power valve or float to high and letting in to much fuel.. OH also is the choke opening up all the way when warmed up.. is it closed to much when cold. When cold there should be about an 1/8" opening unless it has a choke pull off.
Also when replacing the points you HAVE TO check the timing and adjust it. point gap or dwell angle WELL CHANGE THE TIMING.
good luck
tim
drewwilson likes this.
pedal2themetai is offline  
post #5 of 11 Old 05-22-2020, 07:28 AM
oldschool74cj5
Registered User
 
Join Date: Jan 2017
Posts: 503
hello

here is the carb section of the 74 FSM. as you will see its not that complicated but there is a few adjustments that will need to be made for it to correctly run. also when you took apart and cleaned. did you soak the castings in some carb dip?

oldschool
Attached Files
File Type: pdf 4-FuelCarburetion.pdf (4.71 MB, 3 views)
drewwilson likes this.
oldschool74cj5 is offline  
post #6 of 11 Old 05-22-2020, 07:33 AM
Fourtrail
Registered User
1974 CJ6 
 
Join Date: Dec 2007
Location: Illinois
Posts: 4,549
Go run the balls off of it before you get too far into the could be's. If it has had minimal driving and likely just short trips over the last 5 years, then the combustion chambers are likely carbon'd up and it needs brought up to operating temp for a sustained amount of time to clean it out. Fill up with quality fuel and add a can of sea foam to the tank and go for a sustained drive running well up into the rpm range before each shift. Then if it is still blowing smoke, more troubleshooting can be performed.
drewwilson likes this.

80 CJ-5, 74 CJ-6, 56 CJ-5
Fourtrail is offline  
post #7 of 11 Old 05-22-2020, 08:07 AM Thread Starter
drewwilson
Registered User
 
drewwilson's Avatar
1974 CJ5 
 
Join Date: Jul 2015
Location: OKC
Posts: 27
Thanks all!

@Fourtrail : Definitely like idea of "running the balls off it", but I am also doing brake work at the same time. Pretty sure the Combo/Proportion valve has seized because of old/contaminated fluid. Getting a new one tomorrow. If any of you have had experience with getting the 74 to flush without tripping the PV, I have another thread at https://www.jeepforum.com/forum/f8/7...-help-4397755/

@oldschool : Picking up points, plugs, wires today. Will work carb adjustment along with install. I am planning on adjusting the idle mixture also. I didn't do the carb work. Took it to a carb shop that a friend uses and recommends. Came back looking brand new. I've been following the TSM for everything (going to burn the Chilton manual!).

@Pedal: Thanks for the info. Timing adjustment is definitely on the to do list when I replace the points.
drewwilson is offline  
post #8 of 11 Old 05-22-2020, 08:14 AM Thread Starter
drewwilson
Registered User
 
drewwilson's Avatar
1974 CJ5 
 
Join Date: Jul 2015
Location: OKC
Posts: 27
@Bagu s: I will adjust the idle air screw when I get back at it today. Will let you know what happens. This carb has a metering rod also, will give that a look as well.
drewwilson is offline  
post #9 of 11 Old 06-03-2020, 02:18 PM Thread Starter
drewwilson
Registered User
 
drewwilson's Avatar
1974 CJ5 
 
Join Date: Jul 2015
Location: OKC
Posts: 27
Adjusted idle mixture crew with no noticeable changes. Makes me think the fuel pump is putting out too much pressure. PO replaced it before I bought it, but maybe he put the wrong one on. Tried to use a Fuel Pressure Gauge but couldn't get a reading, although the CJ started fine and ran with no problems. Some FLAPS sell fuel pumps that "fit" a 258 I6, but they push out 6.5 PSI and the TSM limits the fuel pressure at PSI to 4-5. I found one with 5 PSI max and will swap them out. Also talked to the guy that serviced the carb, he only disassembled, cleaned, ensured all valves etc were tightened to factory specs, adjusted float and metering rod, and replaced gaskets. He did not do a serviceability check on valves/metering rod, etc. I am going to go though it myself with a rebuild kit from Mike's Carburetor. Any suggestions on the rebuild or ideas on what I am overlooking?
drewwilson is offline  
post #10 of 11 Old 06-03-2020, 04:18 PM
pedal2themetai
Registered User
1956 CJ5 
 
Join Date: Apr 2015
Location: Boise
Posts: 1,559
Quote:
Originally Posted by drewwilson View Post
Adjusted idle mixture crew with no noticeable changes.
HI ?? when you turn the mixture screws in all the way it should KILL the motor when at idle? unless there is a vacuum leak, idling to fast or getting to much fuel from other sources. are you sure the float is set right..
good luck
tim
pedal2themetai is offline  
post #11 of 11 Old 06-07-2020, 04:19 PM Thread Starter
drewwilson
Registered User
 
drewwilson's Avatar
1974 CJ5 
 
Join Date: Jul 2015
Location: OKC
Posts: 27
Update-- Carburetor problem is fixed. I bought a kit from Mike's Carburetor (great site and videos/instructions). Replaced the old float (suspected a pinhole leak) and adjusted drop. Replaced pump diaphragm and adjusted metering rod (thanks Bagus!). Reassembled and...no more black smoke in the exhaust. Still "putts" a bit at cold idle, but smooths out when its warm. Need to adjust the idle mixture/speed a bit I think, but WAY better than it was. Feeling a little hesitation (missing?) when driving now through. Now I need to do points and timing. Being a noob to carburetor & computerless Jeeps, I am going to start another thread about that.

Thanks to all for the advice. If you have any to give regarding timing and points, I'd appreciate any further assistance.
drewwilson is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com 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 e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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 Off
Pingbacks are On
Refbacks are On

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