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willysmjeeps.com :: View topic - M381 near total loss of power
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M381 near total loss of power

 
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RichJohnson
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Joined: Apr 15, 2005
Posts: 130
Location: San Diego CA

PostPosted: Mon Jul 01, 2019 8:14 pm    Post subject: M381 near total loss of power Reply with quote

So I rebuilt my carb right before our club rally in april and Wes schooled me about the check ball and weight becuase it would not start. After that the jeep ran ok. Well over the week of driving around at the meet the jeep started to run worse and worse and not start. My friends suspected a failing coil since it ran worse the longer it ran.

This week I put in a new coil and points and condensor and now the jeep starts really well but it has no power. When warmed up, at an idle in neutral if I step on the throttle, it nearly stalls, pops and kinda backfires then slowly sputters up to speed.
When driving it will barely get moving starting off in 1st gear.

I removed the carb and went all back through it cleaning everything out again and re installing it with no improved results then I removed the seat and fuel pickup and blew through it to verify it wasnt clogged. Its been years since I was in my tank and I just wanted to check.
I think fuel deliver is ok.

We did a compression check and I have 115 115 125 130
A vaccuum test showing a bouncing reading back and forth of 14-18. The manual says this indicates worn valve guides.
I do not know how to deal with that, but it cant be a new problem so Im wondering if this really would cause the near total loss of power or if I am missing something else?
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"Those who enjoy freedom must endeavor to preserve it"

KI6EZA
1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
MBT
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wesk
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Joined: Apr 04, 2005
Posts: 14234
Location: Wisconsin

PostPosted: Mon Jul 01, 2019 11:39 pm    Post subject: Reply with quote

You rebuilt the Distributor? Have you confirmed proper operation of the governor advance (Centrifugal Advance). You need a timing lamp. Your static ignition timing should be 5 degrees before TDC. At idle your timing should be 5 degrees before TDC. As you advance the throttle the centrifugal weights below the point plate will automatically start to advance the distributor timing up to a max of 11 additional degrees of advance or 16 Degrees BTDC. If this governor system is not working then off idle performance will be poor and power will be limited. In the last chart I posted below remember the centrifugal advance numbers are above or in addition to the basic 5 Degree start setting. IE 1, 6, 10, 11 will actually represent 6 Deg BTDC, 11 Deg BTDC, 15 Deg BTDC and 16 Deg BTDC.

Review my ignition system photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=album119&op=modload&name=gallery&file=index&include=view_album.php








This is the centrifugal advance mechanism (Governor advance) hiding under the points plate.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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RichJohnson
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Joined: Apr 15, 2005
Posts: 130
Location: San Diego CA

PostPosted: Tue Jul 02, 2019 9:48 am    Post subject: Reply with quote

Ok I will go through all of this tonight and run it by my jeep buddy. Maybe even pull the distributor back apart.
I did rebuild the distributor about 15 years ago when I restored the jeep. I put an nos kit in it. I did notice the weights were rusty when I had the points plate out the other day. But everything here rusts near the ocean.

My jeep starts and idles fine, its the acceleration that just is not there as it feels like fuel isnt being delivered but Im pretty sure it is.
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"Those who enjoy freedom must endeavor to preserve it"

KI6EZA
1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
MBT
GRC-122 TTY rig
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wesk
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Joined: Apr 04, 2005
Posts: 14234
Location: Wisconsin

PostPosted: Tue Jul 02, 2019 9:52 am    Post subject: Reply with quote

And the entire purpose of the centrifugal advance is to allow better acceleration. Rusty distributor internals are not a good thing no matter where you live.
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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
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Mike_B
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Joined: Dec 10, 2017
Posts: 105
Location: Southern Maryland

PostPosted: Tue Jul 02, 2019 3:23 pm    Post subject: Reply with quote

If it were me I'd test the weights before I take it apart.

Hook the timing light up and see if the mark moves as you rev the engine up...no movement means you found the problem.

Mike B Smile
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Mike B
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RichJohnson
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Joined: Apr 15, 2005
Posts: 130
Location: San Diego CA

PostPosted: Tue Jul 02, 2019 7:35 pm    Post subject: Reply with quote

I didnt read that till now. I opened up the distributor and checked the weights and they moved easy. I also put a light coat of oil on them at my friend suggestion.
I finally got the timing good enough to get it started again but Im going to have to get it back up to the driveway where I can plug my timing light in and use it. My light runs on 110vac.

I dont think that this is the issue.
It feels so much like its not getting the fuel to get going when I stomp on the pedal or even just try to slowly accelerate. I feel like im doing something wrong because Im so frustrated with it. The carb looked fine when I took it all apart and went back through it but it feels like the accelerator pump just isnt moving, just like it did early this year before I rebuilt it. I doubt the diaphram went bad this fast in just 3-4 months.
_________________
"Those who enjoy freedom must endeavor to preserve it"

KI6EZA
1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
MBT
GRC-122 TTY rig
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RichJohnson
Member


Joined: Apr 15, 2005
Posts: 130
Location: San Diego CA

PostPosted: Wed Jul 03, 2019 9:57 pm    Post subject: Reply with quote

Thanks for the help everybody.
Yes the timing advanced just fine.

The short answer is, the vacuum gauge tells all. I have some worn valve guides indicated by the vacuum bouncing 15-20 at this time. The oil getting by fouled my rear plug. Simple as that. I have never had a misfire circumstance so I didnt know what it feels like.

My old jeep buddy came over and drove it tonight around the block and said, your misfiring. Your rear plug is probably fouled..... Oh well nothing like experience.

I wound up replacing my coil, points, condensor and capacitor and going through the carb a few times and checking the fuel pump.

I can make the parade now, but Im gonna have to get a valve job or some how have the guides fixed.
I dont know how to go about that job and kinda bummed as I rebuilt the engine about 15k miles ago.
_________________
"Those who enjoy freedom must endeavor to preserve it"

KI6EZA
1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
MBT
GRC-122 TTY rig
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View user's profile Send private message Visit poster's website MSN Messenger
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 14234
Location: Wisconsin

PostPosted: Wed Jul 03, 2019 11:27 pm    Post subject: Reply with quote

Quote:
I dont know how to go about that job and kinda bummed as I rebuilt the engine about 15k miles ago.


The quality of the rebuild depends on the quality of the shop. Choose your next auto machine shop carefully.

Your next step this time before tossing more money at a suspected problem is to do a leak down test on all 4 cylinders. The Vac readings you got point to a valve issue but I for one would not automatically assume worn guides. Sticking valves, damaged seats and burned valves can give the same symptoms. Improperly adjusted valves can also cause that type vacuum reading. Arm yourself with a good set of manuals and read thru them. Often times the civilian manual can be more helpful then the military TM's.

You can find it in my photo album:
http://www.willysmjeeps.com/v2/modules.php?set_albumName=album305&op=modload&name=gallery&file=index&include=view_album.php


SM-1046 Kaiser Service Manual for post 1954 CJ's


It has a very good troubleshooting page!
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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
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