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M38 carb sweating?
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Keith
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Joined: Feb 18, 2008
Posts: 113
Location: Wauchula, Florida

PostPosted: Thu Jan 21, 2010 3:26 pm    Post subject: M38 carb sweating? Reply with quote

I'm still trouble shooting, my last post "dist cap test" has the details of all the trouble shooting I've done.

What are the causes for the lower part of the carb to sweat?

With everything I've done it still won't idle and alot of black smoke at low rpms. Last night it ran out of gas which is weird because I put a couple of gallons in it a couple of weeks ago when it ran out of gas during my trouble shooting and I haven't drove it any and it hasn't ran much at all which makes me think the carb is messed up. Thats alot of gas to be consumed.

The gas tank was dipped and coated, new fuel line, and filter.
I've checked the float level and needle valve.
No trash in the carb.

Could it be one of the diaframes are damaged allowing to much fuel through?

Thanks
Keith
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Stir-stick
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Joined: Jul 27, 2009
Posts: 37

PostPosted: Thu Jan 21, 2010 10:05 pm    Post subject: Reply with quote

Keith, Are you referring to the cast iron throttle body(base) ? It gets cold and sweats.Are the two springs in the correct locations on the diaphrams ? Check float level.Check fuel pressure.Good Luck. STICK
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wesk
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Posts: 16225
Location: Wisconsin

PostPosted: Fri Jan 22, 2010 12:21 am    Post subject: Reply with quote

That is condensation on the metal surface of a venturi which physically lowers the temp of the vapor flowing through it. Common occurrence when you run it a long time in the garage in a high humidity environment.

I hate to be the bearer of tough news but what is going on here is called "Shotgunning" a problem instead of troubleshooting a problem. Shotgunning means you get a lot of unrelated ideas in no particular order thrown out there and you try different tests willy nilly instead of following a detailed and orderly troubleshooting chart.

I turn wrenches for a living. The majority of my work is done on a flat rate standard. To insure the customer doesn't get walzed around the block for a lot of extra hours and money. I lay out that vehicles troubleshooting checklist and follow it with a note pad right there recording the results of each test and check. Those checklists are organized into the most likely causes with the least amount of time and parts spent first. Then the more time and money consuming checks towards the end. They also will usually stick with one system at a time.

There are very well thought out charts in those TM's you have. When using them they become more useful when you apply a bit of common sense to each step. And check related items at the same time.

For example I'll use the M38A1 TM 9-8014 Troubleshooting Pages 79 thru 99.

Par 81c is a good place to start. "Engine starts but will not run"

1-Check air cleaner for plugging up.
This implies a restriction of air flow may exist so one should go a little further here and check the induction plumbing, tubes, hoses for blockage. Believe it or not we forget and leave rags in those opening, critters move in to them when it gets cold out and so on. Check to make sure the choke plate is opening all the way. Make darn sure both fording valves are in their correct position!
2-Check fuel system supply.
Here we see black smoke which means rich so look for things in the fuel supply system that will make her too rich. Float level set to high, Float sticking down or needle sticking open. Fuel pump pressure too high. Torn or damaged diaphragms in the accelerator pump and metering rod vacuum bays. Diaphragm springs reversed between chambers aor on wrong side of diaphragm. This can happen easily. Also the TM 9-1826A illustration shows the spring on the wrong side of the diaphragm!
3-Check spark plugs.
Steps 4, 5 & 6 can be shortened by simply after removing and inspecting and cleaning if needed re-install the 4 spark plugs on the ends of each of their shielded leads. Lay them down and crank the engine while checking for good blue spark on all four. If you have good spark then disregard all of those steps I listed except checking ignition timing.

Checking timing can be very painless. Remove the distributor cap. Get #1 piston TDC on compression. Back up the crank until your timing mark shows about 10 degrees before TDC. Look at the points. They should be closed. Take a small piece of paper and slip it between the point contacts. Now apply a gentle pull on that piece of paper just to tension it. Now slowly turn the crank towards the 5 deg mark and the instant the paper slips out of the points stop. Thats where you timing is set. If it's between 4 & 6 and the plugs spark fine then no need to putz with the ignition any more.

If you have not yet resolved the problem then move on to par. 82c "Engine Floods" and follow that checklist.

Write down on a piece of paper the paragraph # of each check and it's results. This record will be a great help to you as move through the checklist.

Patience, and organized troubleshooting checklist, a record of each test result and discipline is the way to solve a problem without throwing unecessary time, money and parts at it.

Wink

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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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Keith
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Joined: Feb 18, 2008
Posts: 113
Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 8:15 am    Post subject: Reply with quote

Thats the problem, that is the order I followed, I've checked everything you mentioned in that order, except completly disassembling the carb and checking the diaframes. again its been running just fine for 6 months since i rebuilt the carb and everything else so springs and all that didn't change and the rebuild kit is from debbelas and I would expect the diaframes to already fail. one of the problems in my patient trouble shooting over the past 4 weeks is the symptoms changed half way through the process and the new symptom turned out to be 2 plugs fowled out. And now that leads me back to the carb being the original problem. I started posting questions about this about for weeks ago. I know in the end its going to be something simple and looking for some insight after checking all the obvious things.

Its very difficult trouble shooting in this manner and I appreciate everyones patients and advise.

Thanks Keith
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wesk
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PostPosted: Fri Jan 22, 2010 8:25 am    Post subject: Reply with quote

If you didn't buy the carb kit from Midwest or AJP or the Carb Shop who all sell brand new modern rubber parts kits then you most likely bought an NOS 30 plus year old kit that has rubber diaphragms that won't tolerate todays gas very long and are leaking. You don't have to completely disassemble the carb to inspect and remove the diaphragms. You just pull the 4 screws from the diaphragm cover right there on the engine. Takes every bit of 2 minutes. Wink
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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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acengraver
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Joined: Jan 14, 2009
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Location: Birmingham, Alabama

PostPosted: Fri Jan 22, 2010 9:18 am    Post subject: Reply with quote

Here's my two cents. I had a similar problem on an M38 carb. It turned out that I had incorrectly installed the top of the carb so that the metering rod completely missed the seat. The Jeep would burn a gallon of gas in about 5 minutes. The rebuild kit idea in the above post sounds like the best idea yet.
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wesk
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PostPosted: Fri Jan 22, 2010 9:32 am    Post subject: Reply with quote

I based my comment on the diaphragms on Keiths note that the carb was rebuilt and ran fine for 6 months. That would rule out an assembly error by about 90% and point towards a part failure.

Since you mention metering rod installation errors I have seen a few incorrect rods used. Especially where the new style carb kits come with parts for both the M38 and the M38A1 carb. The rods are very similar in appearance. But they do have the Carter numbers on them.


This is the new style kit and you can see the two rods side by side.




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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


Last edited by wesk on Fri Jan 22, 2010 10:24 am; edited 1 time in total
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Keith
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Joined: Feb 18, 2008
Posts: 113
Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 9:56 am    Post subject: Reply with quote

thats my next plan of action and I thought Debellas carb kit was a new one I'll have to get the next one from midwest.

Thanks
Keith
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Keith
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Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 10:08 am    Post subject: Reply with quote

the kit i got is different from the one pictured. my diaframes are black in color and did not come with new screws and thats just the obvious ones i wonder what else is different?

Thanks
Keith
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Keith
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Posts: 113
Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 10:48 am    Post subject: Reply with quote

ok I just pulled both diaframes off and and here's what I found. they are not black in color but grey. No cuts, cracks, splits BUT it does appear that the gas has dissolved some of the rubberlike material everywhere gas has came into contact with I can see the cloth substructure.
my metering rod is closet matches the m38 ro but not exactly
overall legth 1.371
the .404 dim is .371 on mine
the dim between the end and the center of the hole is .319 and I'm not sure if its supposed to be .320 or .370 in the picture.
75595S is stamp on it
I can see the tooling marks left from the machining process on the small round end, point being it has been ground off or something else.

Thanks
Keith
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Keith
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Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 10:51 am    Post subject: Reply with quote

Were did you get the kit pictured? The more I study it the more things I realize that mine did not come with and the more upset I get!!!

Thanks
Keith
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wesk
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PostPosted: Fri Jan 22, 2010 11:12 am    Post subject: Reply with quote

Hello Keith,

Looks like you have solved your rich running problem. The kits with all new material are $55 from either Midwest Military or AJP.

75-595S is the M38 metering rod.

I'd buy the kit and install the new diaphragms, springs and metering rod and see what you get.
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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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Keith
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Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 11:22 am    Post subject: Reply with quote

So did you think its the short metering rod or the diaframes or both?
Thanks
Keith
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Keith
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Location: Wauchula, Florida

PostPosted: Fri Jan 22, 2010 11:52 am    Post subject: Reply with quote

I just got off the phone with john @ midwest and he explained to me about 6 months ago when I got my carb kit from debellas they all were out of stock on the major overhaul kit (due to manufacturing delays) and that I must have gotten the minor kit. But he has the major kit again and is sending one out to me. He also mentioned that he has had trouble with these kit in Florida due to the gasoline blended for Florida. Do you or any one else know of this problem? Can I put any additive in the fuel to help prevent this? I've been adding Stay-bil to all my fuel. Florida does advertise 10% or less Ethanol in the fuel who knows what else!!

Thanks Keith
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GPA
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Posts: 216
Location: Hungary

PostPosted: Fri Jan 22, 2010 1:32 pm    Post subject: Reply with quote

My M38A1, when it was still running (grounded with cracked block for a year) always ran rich. No hesitation, started cold very easily without choke, but rich. After carb disassembly I had discovered the problem. The metering rod at the section in the sleeve at the diaphragm, was not drilled for the pin! The rod always sat at rich position hence no trouble at cold start and no hesitation on acceleration. I did not fit any low quality kit it was that way when I bought it. Carb is rebuilt now, but as the jeep is down it is in my workshop office on a shelf as a decoration, I hope not for long.
On an other M38A1 last year I did a carb overhaul for a customer. Against all the warnings by Wes and other guys I had fitted a Mickey Mouse rebuild kit because I already had it. It was made by APCO or NAPCO. I thought because I have extensive experience in carb repair, overhaul and calibration it will be a piece of cake. I did manage it, but it was not a two minute job. For somebody with limited experience the more expensive kit at $55 would be a lot cheaper and less headache as well. I am not talking about the old rubber diaphragms either. There are other problems with this kit as well.
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