Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Mon Jul 01, 2019 8:14 pm Post subject: M381 near total loss of power
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? _________________ "Those who enjoy freedom must endeavor to preserve it"
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.
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Tue Jul 02, 2019 9:48 am Post subject:
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. _________________ "Those who enjoy freedom must endeavor to preserve it"
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. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Tue Jul 02, 2019 7:35 pm Post subject:
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"
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Wed Jul 03, 2019 9:57 pm Post subject:
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"
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.
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