Engine cutting out

[MajBen]

Hi, after a long absence due to a situation beyond my control, I am trying to get Leatherneck (my M38) project completed. As several of you know, I have only some 8 or 10 items left to have it 'factory' to the best of my knowledge and I have the parts needed. Keith Buckley, whom many of you know is well respected for his knowledge of M38s, told my neighbor, John Kelsey of Kelsey tires, it was pretty slick---made my day.

My problem is and has been that after it reaches temperature, it begins to stutter or cut out. This problem has existed since I nearly had it finished and due to this mainly, it has only about 20 to 25 miles put on it. I think the last time it driven was some 18 months ago. Yesterday with a new battery, it started immediatelyi and ran like a top until it reached temp and started the cut out problem. At one time, some of you made some suggestions for me to check but never had the opportunity to do so and have since lost track of them. Would you please offer any again that you might think of.

Leatherneck as I said it almost complelted with everything NOS or original as possible and everything checked---every single bolt was removed to start and many body parts replaced including a NOS front floor and I have long forgotten many details.

The one thing my son and I noticed yesterday that I don't think I noticed before is that there appeared to be a small amount of real thick oil or grease aound the bottom of the carb gasket and for the life of me, I can not think of any reason for this situation---this is a real small amount that we scraped off with a screwdriver---would this lead to the problem?

Any help you can give me would be greatly appreciated. Semper Fi Ben
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Semper Fi Ben M38 & M100

[skyjeep50]

Could be several things but there have been other posts recently fingering a coil going bad as one of the causes of poor ignition when the engine warms up.
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1951 M38

[MajBen]

Hi Skyjeep50, thanks for the information; seems as if that was one of the long ago suggestions. As I recall, I don't have a spare coil but do
have a NOS distributor so I can borrow one from there temporarily. Semper Fi Ben
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Semper Fi Ben M38 & M100

[rwbow1969]

Ben, Check out some of the items in the rough starting forum. Wes pointed out some good things to check. Good luck and do you have any pictures?
Rob

[wesk]

Ben's photo album is at:
http://www.willysmjeeps.com/v2/modules.php?set_albumName=Ben-Daugherty&op=modload&name=gallery&file=index&include=view_album.php
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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

[MajBen]

Thanks rwbow 1969, I found the post you recommended and will try coil first. Thanks and Semper Fi Ben
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Semper Fi Ben M38 & M100

[oilleaker1]

Coil was my first thought, the wet build-up at the base of the carb is most likely gas from a float level or dirty needle and seat situation. Too much gas getting by somewhere would also cause a bad idle. A leak at the base gasket would definately cause a bad idle. You will find it sooner or later. John

[MajBen]

Hi Thanks for all the response. My problem is not only not resolved but it has become worse---when we let it shut itself down, it will not start until it cools completely---over night in our test. Then, the only way it will start is to hold the footfeed all the way to the floor and it reacts as as if it is flooded but finally starts and runs great until it reaches a certain temperature.

rwbow 1969 referred us to a post by Wes entitled 'rough starting.' We found this to be an excellent article and we are convinced that the heat being absorbed as Wes suggest is causing the problem.

We believe that our problem lies more likely than not withing the ignition system rather than fuel or vacuum. Most suggest that the problem is coil related. We have 3 coils, two used and one new one in a complete NOS distributor. The same problem of cutting out completely when hot and not starting remains with both coils. We have not removed and tried the new coil as we want to retain the integrity of the NOS distributor.

We want to install the new distributor but believe that it needs to be lubricated as it has been in storage for so many years. A few years back, Wes provided suggestions as to how to properly lubicate a NOS distributor but I have lost this information.

Anyone that can lead me to that post or has knowledge of how this should be done, please let us know---it could have been on g503. Because this is so important to us and the fact that this request may be lost within this thread, I am going to post a new topic just for this information.

Thanks again and any suggestions of any kind you may have, please let us know. SemperFi Ben
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Semper Fi Ben M38 & M100

[MajBen]

Hi all, just an update. We have exhausted our search for an answer as we still have the problem. We have gone through several stages. We solved the flooding problem by disconnecting the hand pump. We have successfully enstalled the NOS distributer, checking the point gap and the timing. Every thing on Wes's "rough start' list has been double checked.

Two question do arise: 1) The list uses the pural with manifold heat riser(s) I know of only one which as the spring on one side and the counter weight on the other and as the heat rises, the flap opens up which appears to be worfking well. 2) Lines from the pump to the carb. Looking at the pictures in the manual, it appears that the fuel line is in a direct vertical line from the pump to where it bends to connect with the carb. In my case, I routed my line so there is about 90 degree slant toward the fender and then horizontal to the carb leaving even more space from the exhaust manifold.

A few years ago when I was first faced with this problem, I posted a topic on eithe 503 or this site asking for help and as I recall, Wes presented another list that had more to do with potential vacuum problem---naturally, I can't locate it now. Wes, if you read this or any one has this list, we would sure appreciate receiving a copy.

In summary, we are back exactly where we were and that it starts without a flooding problem, runs great from our house in the subdivision to the main highway and back about 2 miles, and then while idling it dies unless we increase the rpm.

Any further suggestions will be appreciated. Semper Fi Ben and Ben
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Semper Fi Ben M38 & M100

[oilleaker1]

Does it run without cutting out when you increase the throttle so it won't die at a idle? When you adjust mixture screw at the carb base does it change the idle speed? Is it at 5 degrees BTDC at a idle?(when running fine) A vaccum leak , too tight of valve clearances, plugged idle circuit, incorrect timing, wrong idle mixture screw adjustment, will all cause a bad idle. I've had all of the above screw up my Jeeps at one time or another. John

[oilleaker1]

Sounds like you have fuel and spark right? I'd start by making sure all the valves are adjusted right, make sure the carb base gasket with the stupid staples, has a thin paper gasket added to both sides, Screws aren't loose or getting loose at the carb base also. Then adjust the mixture screw and stop screw to get it up to 650 RPM's or so and check the idle ignition timing. If all is well, and then it changes and won't idle, screw the idle mixture screw in and out. If it doesn't change, you have something like dirt or foreign material in the idle circuit. Make sure the throttle stop screw isn't backing out and closing the throttle ( had that too!) You have covered the rest : coil, fuel delivery, just the idle is messed up I take it. Loose vaccum wiper system hoses, valve, fuel pump vaccum ports and tubing to the intake vaccum port should be checked. Disconnect the vaccum at the intake port and plug it in a test. John

[artificer]

Rather than jump all over the place if you hook up a vacuum gauge to the intake manifold, what readings do you get? This is on thing that can be done very quickly & it can eliminate many potential problem sources plus possibly point you in the right direction.
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John GIBBINS
ASE Master Medium/Heavy Truck & Auto Technician 2002 USA
Licensed Motor Mechanic NSW # MVIC 49593 Current
YOU CAN'T TROUBLESHOOT WHAT YOU DON'T UNDERSTAND

[MajBen]

Hi guys, thanks for the information;we have checked the things that oilleaker 1 has suggested---remember, this jeep has had a complete and thorough rebuild.

Artificer, you bring up a new suggestion. It has been years since I did such a test. Would you be more specific or give me a reference that describes exactly how to go about this and what results I want and do not want---would these results appear all the time or just when the engine is hot?

I guess our next step is to unhook, one by one, each and every vacuum line and see if we detect a difference.

We were convinced that we had an ignition problem, and may still have, but with the installation of 3 coils, one new, and using two sets of points, condensors, etc, one set new, we think we have eliminated that possibility, but one can never be sure.

Now, we are thinking more of the fuel system since giving more gas as it begins to die will straighten it out; yet, we have a newly rebuilt carb by a professional who has gone through it the second time. The fuel pump was rebuilt by a professional and the problem began as soon as we completed the initial phase of the rebuild some 5 years ago, so I don't think a diaphram would be involved. But, just how does one check a fuel pump at idle when the engine is hot? Thanks guys and semper fi Ben
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Semper Fi Ben M38 & M100

[Oldsalt]

I hate to butt in since you seen to have a bunch of highly experienced Jeepers here helping but I've noticed a couple of things that you haven't mentioned.

On the ignition, you mention coils, points, and condensers but how about the cap or rotor? Not like given the pattern you describe, but easy to check.

Have you tried to check for vacuum leaks by squirting something at the common leak points? You can spray carb cleaner or something similar at places like the carb base gasket, or intake manifold gaskets and listen for a change in the engine. If you hit a leak it will smooth out, or speed up, or even quit. Any change will indicate a leak. Obviously you need to be very careful about the spray flashing off if you hit something hot.

Does pulling the choke out slightly when it is cutting out make it worse or better?

Any chance the fuel tank is not venting and is starving the carb for fuel?

Has anything you've tried made any difference at all in the pattern of the problem?

When it starts cutting out, is it a steady miss or does it seem random or involve more than one cylinder?

I know this a pretty random list but I'm just trying to hit possibilities that haven't been mentioned in this thread before.

[MajBen]

Hi Oldsalt, that handle sounds like Navy or USMC, right? Anyway, you certainly are not butting in as you bring up some new and really good points. First, the cap and rotor are new with the complete NOS distributor so with the old and new I have two for test.

You may really be on to something with the vacuum leak test and we will try what you suggest---we wanted to but didn't really know how to go about it.

We have checked the gas tank by removing the cap and it makes no difference. Yes, if one pulls out the choke, it will straighten out, I think but will try that again; I know that by pressing on the accelator, it will straighten out.

I'm not sure exactly what you mean by when it starts cutting out is it a random miss. In my best explanation, it is idling just super than it will miss and then right itself, a few seconds later it will miss a couple of times and then straighten out and the third or fourth time, it will just continue missing until it dies, unless you hit the footfeed.

Old salt, thanks, you have given us some specific concrete things to try and along with the vacuum test, hopefully we will get this whipped. I hope I hear more about the vacuum test as I ask above soon as we want to try it. I have a vacuum gauge and might have some instructions but not sure. I think but not sure that there is a removable plug on the front of the intake carb---separated from the jeep and tools at the momnt. Semper Fi Ben
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Semper Fi Ben M38 & M100