Create an account Home  ·  ·  Forums  ·  ·  Articles  ·  ·  Downloads  ·  ·  Photo Gallery  
Login
Nickname

Password

Don't have an account yet? You can create one here.

Navigation
· Home
· Article Archive
· Article Submit
· Downloads
· FAQ
· Forums
· Members List
· Photo Gallery
· Private Messages
· Web Links
· Your Account

Search Articles



Forums

M38A1 valve adjustment
M38 Fording Cable Bracket
Photo Gallery Request
M38 Front Frame Specs
What's a fair price on M38 Parts?
for you m170 fans
M38 Top Bow pivot point hardware
FS: Fully restored 1955 M38A1
Carb Bracket
M38 Parts for sale

Willys M Jeeps Forums


willysmjeeps.com :: View topic - M38A1 carburator issue
 Forum FAQForum FAQ   SearchSearch   UsergroupsUsergroups   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

M38A1 carburator issue

 
Post new topic   Reply to topic    willysmjeeps.com Forum Index -> Technical Knowledge Base
View previous topic :: View next topic  
Author Message
lake
Member


Joined: Aug 24, 2009
Posts: 32
Location: Nova Scotia ,Canada

PostPosted: Sun Jun 15, 2014 1:33 pm    Post subject: M38A1 carburator issue Reply with quote

Thought I had a coil issue with my 1953 m38a1,so I replaced it with a new one from Kaiser willy,s auto ,but still no change in the rough running of the jeep.It will run good for aboat 10minutes then gets real sluggish running and seems to be missing real bad and then will quite and will not start for about 15mins or so.Could it be a carurator problem like maybe to much fuel or maybe a need of a kit for the carburator.The spark plugs are fairly new so I elemented that,so I am in need of suggestions.thanks Lake
Back to top
View user's profile Send private message
Bearbait
Member


Joined: Aug 24, 2013
Posts: 19
Location: Saskatchewan, Canada

PostPosted: Sun Jun 15, 2014 4:50 pm    Post subject: Reply with quote

A couple things to check before throwing parts and money at it.
Check point gap and condenser.
Check your spark plugs after it stalls, plug wet probably a spark issue, plug dry probably a fuel issue.
Check for a plugged vent in fuel tank (plugged gas cap vent will cause fuel issues).
Fuel line vapour lock can be caused by fuel lines running to close to engine hot spots like exhaust manifold coolant lines etc.
If these things fail check fuel pump output and pressure.
I hope this helps you.

Brad
_________________
Brad Young
Expensive habits:
1971 M38A1
1967 Mercury steps side short box
1978 Porsche 924
Back to top
View user's profile Send private message
lake
Member


Joined: Aug 24, 2009
Posts: 32
Location: Nova Scotia ,Canada

PostPosted: Sun Jun 15, 2014 6:00 pm    Post subject: Reply with quote

ok thanks ,I,ll recheck the points ,the plugs are dry and the fuel pump is fairly new,I am thinking maybe the diaphram in the carburator ,but not totally sure.The fuel filter is totally full of gas which seems like to much fuel may be getting to the carburator .but not quite sure if this is normal
Back to top
View user's profile Send private message
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 15045
Location: Wisconsin

PostPosted: Sun Jun 15, 2014 6:58 pm    Post subject: Reply with quote

The most common cause of your symptoms is the third item above. PLUGGED TANK VENT SYSTEM. The very first and simplist test you need to make is remove the gas cap and start and drive the jeep. No more problem unplug the tank vent system. It may be as simple as correcting the position of the cap's fording valve or you may have a non- selectable cap vent. in which case you will need to unplug the vent over next to the pickup and sender.


This is the selectable vent cap which you may have. The other style cap is un-vented.


This is the later M38A1 tank vent. Earlier M38A1 that came with deep water fording capability had a tube connected here that ran to the air cleaner. In either case make sure the vent valve (late system) or the vent line (Early system) is not plugged.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
Back to top
View user's profile Send private message Send e-mail Visit poster's website
lake
Member


Joined: Aug 24, 2009
Posts: 32
Location: Nova Scotia ,Canada

PostPosted: Mon Jun 16, 2014 4:10 am    Post subject: Reply with quote

Ok,I checked the gas cap and it is already in the open position,but i will check out the tank fent tonight thanks.Should the gas filter be totally full of fuel,because my is and I don,t remember it always full to the top.(maybe to much fuel possible to the carb ???)
Back to top
View user's profile Send private message
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 15045
Location: Wisconsin

PostPosted: Mon Jun 16, 2014 7:03 am    Post subject: Reply with quote

Fuel pressure and flow are generally a constant and do not change during operation much.

An engine that runs smooth and starts easily then when it warms up runs poorly and then quits and won't restart until it cools down has trouble with something easily affected by heat buildup. Change the condenser and bypass the radio noise filter capacitor found in the main power receptacle for the distributor. Both can fail as they get warm and work fine cool.

http://willysmjeeps.com/v2/modules/gallery/albums/album121/Late_M38_Distributor_internal_wires.sized.jpg
This is the radio noise filter.


This is a fabricated eliminator for it.



Also cracks in the distributor block will often expand with heat and create issues.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
Back to top
View user's profile Send private message Send e-mail Visit poster's website
skyjeep50
Member


Joined: Feb 20, 2007
Posts: 606
Location: Illinois

PostPosted: Mon Jun 16, 2014 7:30 am    Post subject: Reply with quote

"Gas filter full to the top" - A stock M38A1's fuel filter is in the gas tank, has a very large surface area and is usually sufficient to flter the fuel - no need for a secondary filter. If your jeep has an aftermarket fuel filter, yes, that might be a thing to check to see if it may be blocked. If the original fuel filter is still in the tank, perhaps it is plugged if there is a lot of crud and rust in the tank and its never been serviced. You have to unscrew the fuel pickup to check. If it is still there and in good condition, ditch the other filter - its not needed.
_________________
1951 M38
Back to top
View user's profile Send private message
lake
Member


Joined: Aug 24, 2009
Posts: 32
Location: Nova Scotia ,Canada

PostPosted: Mon Jun 16, 2014 9:46 am    Post subject: Reply with quote

ok thanks ,I will start with the condenser first,the jeep starts great, sounds great and even exelerates great,when cold, or for the first 10-15mins and then really starts to miss once warm.???
Back to top
View user's profile Send private message
lake
Member


Joined: Aug 24, 2009
Posts: 32
Location: Nova Scotia ,Canada

PostPosted: Mon Jun 16, 2014 3:20 pm    Post subject: Reply with quote

just remembered the points and condenser was new last year and was picked up at napa auto.But I am not sure if they sold me a 24 volt condenser or a regular 12volt.Would this be a possible issue ,to make the engine break down after warming up.Maybe I should try a 24volt condenser ??
Back to top
View user's profile Send private message
lake
Member


Joined: Aug 24, 2009
Posts: 32
Location: Nova Scotia ,Canada

PostPosted: Wed Jun 18, 2014 8:32 am    Post subject: Reply with quote

I have replaced the condenser and coil with a new ,but still no change.I removed the spark plugs and they seem to be very black with carbon .The plugs are only 1 year old, so I cleaned them again and the jeep started and ran fine for another 15 mins or so,Well I guess I am still puzzled and My M38A1 still remains in my garage at rest. ????:
Back to top
View user's profile Send private message
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 15045
Location: Wisconsin

PostPosted: Wed Jun 18, 2014 8:53 am    Post subject: Reply with quote

Have you bypassed the radio noise filter capacitor yet?
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Birdy
Member


Joined: Oct 08, 2016
Posts: 1
Location: Alberta, Canada

PostPosted: Tue Jul 21, 2020 10:31 pm    Post subject: Reply with quote

This past weekend during a convoy run, my M38A1 began to run very rough and guickly stalled out just after cresting a long hill, barely allowing me time to get off the road. I could not restart and had to get towed home. Luckily I was less than 10 miles from home.
Thinking this was a failed coil, when I got home I went through my distributor and replaced coil, points and condenser. I also cleaned the plugs, and the jeep fired right up and idled perfectly. I took off again in attempt to re-join the group on their return trip. Well I got about 3 miles down the road and it started missing and sputtering. I turned around and tried to get back home, and didn't quite make it. Had to get towed again!
Over the last couple of evenings I tried my spare carburetor, spare fuel pump, checked for water in gas, went through the distributor at least 4 times, checked air cleaner, checked fuel and vent lines, spark on all cylinders, timing, etc, etc... No luck.
Then last night I came across the post above by Wes related to the radio filter. I changed that out today, and.... the jeep runs perfectly as it did before! I was blown away, but so happy to solve the issue. Thanks Wes!!
I have replaced those filters with new ones in the past, but that is the first time I have ever had one fail. It is a very confusing set of symptoms.
I will be making the direct wire assembly as shown above to eliminate that filter.
Anyway, I just wanted to pass this on so others may save themselves a lot of pain and suffering if they experience the same issue.
Thanks again Wes.
Back to top
View user's profile Send private message
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 15045
Location: Wisconsin

PostPosted: Tue Jul 21, 2020 10:44 pm    Post subject: Reply with quote

Glad it worked out for you!
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    willysmjeeps.com Forum Index -> Technical Knowledge Base All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Powered by phpBB © 2001 phpBB Group
Forums ©

 



PHP-Nuke Copyright © 2005 by Francisco Burzi. This is free software, and you may redistribute it under the GPL. PHP-Nuke comes with absolutely no warranty, for details, see the license.