Forum Home Forum Home > CJ-2A Discussion Area > Tech Questions and Answers
  New Posts New Posts RSS Feed - Backfiring through the Carburetor
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Backfiring through the Carburetor

 Post Reply Post Reply
Author
Message
Jack Williams View Drop Down
Member
Member


Joined: 09 Aug. 2014
Location: Iowa
Status: Offline
Points: 24
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack Williams Quote  Post ReplyReply Direct Link To This Post Topic: Backfiring through the Carburetor
    Posted: 18 July 2017 at 1:23pm
I have a 1948 CJ2a. After being stored for the winter it wouldn't start. I replaced the fuel pump, put in new spark plugs, replaced the distributor wires, rebuilt the carburetor, replaced the points and condenser,installed a new rotor, and a new distributor cap. It still wouldn't start. We finally found that the post that holds the points in the distributor came loose. I purchased a replacement distributor. I took it to a professional mechanic for installation.
Once installed the engine would run, but ran very rough while backfiring through the carburetor and exhaust. It would produce very little power.

I found a replacement distributor plate with a solid post. I installed new points and condenser and reinstalled the original distributor. Now it won't start at all. I believe the problem with the original distributor is that it is not installed properly and is not firing in time with the engine. I noticed the oil pump had been turned at some point because the 1. distributor wire was not at the 5 o'clock position. I followed Walke's video to do the installation and find the correct position for the distributor, but it still won't fire. My questions are:

1.) Any ideas why the engine would backfire while running with the replacement distributor?
2.) Any ideas on how to properly install the distributor so it is timed to the engine properly?

Thanks

Jack Williams
Jack
Back to Top
athawk11 View Drop Down
Member
Member
Avatar

Joined: 17 Jan. 2012
Location: Arvada,Colorado
Status: Offline
Points: 3880
Post Options Post Options   Thanks (0) Thanks(0)   Quote athawk11 Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2017 at 1:33pm
Hi Jack,

Every time I have had  a back fire from the carburetor, I have found that I installed the spark plug wires in the wrong order.  I don't do this anymore, but early on, I had a bad habit of installing the wires in a "clockwise" order.  They fire in a "counter-clock-wise" order.  
1- 1946 CJ2A   
2- 1949 CJ3A
Back to Top
Stev View Drop Down
Member
Member

Sponsor Member

Joined: 27 July 2016
Location: Cincinnati
Status: Offline
Points: 2036
Post Options Post Options   Thanks (0) Thanks(0)   Quote Stev Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2017 at 1:38pm
Jack,

1.  Could be lots of reasons for back firing through the carb - my guess is you have an intake valve opening a the wrong time, a intake valve that is stuck open or a burn intake valve.    Similar for the exhaust.  

2.  The oil pump needs to be removed and indexed correctly so that the tang slot for the distributor is in the correct position so the distributor's rotor ends up in the factory position and reinstalled.   


Edited by Stev - 18 July 2017 at 1:40pm
Stev
1946 CJ2A Trail Jeep (The Saint), 1948 CJ2A Lefty Restored
Back to Top
ggordon49 View Drop Down
Member
Member
Avatar
Sponsor Member

Joined: 30 June 2017
Location: Connecticut
Status: Offline
Points: 1248
Post Options Post Options   Thanks (0) Thanks(0)   Quote ggordon49 Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2017 at 1:47pm
I am hesitant to reply because I'm by no means a mechanic... I did however, experience back firing through the carburetor after one of my project had sat over winter(s).... It ended up being the valves were stuck open Confused. Took a couple days of soaking with Marvel & PB and couple careful hits with a brass dowel through the spark plug holes, but they went down.
Back to Top
Ol' Unreliable View Drop Down
Member
Member
Avatar

Joined: 25 Sep. 2016
Location: CO Springs CO
Status: Offline
Points: 4124
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2017 at 11:26pm
Originally posted by athawk11 athawk11 wrote:

Hi Jack,

Every time I have had  a back fire from the carburetor, I have found that I installed the spark plug wires in the wrong order.


If a mechanic who doesn't know old Jeeps well did the job, this is your most likely problem.
There's a reason it's called Ol' Unreliable
Back to Top
stude-a-willys View Drop Down
Member
Member
Avatar

Joined: 02 Sep. 2014
Location: Conifer, CO, US
Status: Offline
Points: 133
Post Options Post Options   Thanks (0) Thanks(0)   Quote stude-a-willys Quote  Post ReplyReply Direct Link To This Post Posted: 19 July 2017 at 1:42pm
Disturbed engine timing.

I didn't know that someone installed the oil pump un-timed to my rig. It is STILL set up this way (wrong by the book that I don't have anyway.)

I used my thumb over the #1 spark plug hole to decide when I was on the compression stroke when I cranked the engine around. I put the timing mark on TDC. This way I'm not "180 out."
Then I set the distributor in the middle of it's range of motion with the vacuum diaphram pointing the right direction.
I pulled the distributor cap off and looked at where the rotor was pointing. OK. That is MY #1 plug tower even if it isn't the "Right" tower for #1.  I moved all the plug wires around based on "MY" #1 and counter clockwise rotor rotation. 

Started right up. Adjusted timing as normal.
I marked MY #1 on the cap for the next time I goof up the plug wires. I also write/draw notes on my air cleaner for the next guy. (usually forgetful me.)

If it still won't fire, check for spark in general. check compression for hung valve.





Studebaker re-powered CJ2a
Back to Top
Ol' Unreliable View Drop Down
Member
Member
Avatar

Joined: 25 Sep. 2016
Location: CO Springs CO
Status: Offline
Points: 4124
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 19 July 2017 at 9:52pm
Stude, it just took you a tad longer because you have that Studebaker 6-cyl under your hood.
There's a reason it's called Ol' Unreliable
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.04
Copyright ©2001-2019 Web Wiz Ltd.