Engine runing rough after warm

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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tnspd
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Engine runing rough after warm

Post by tnspd » Fri Aug 12, 2016 6:52 am

A couple of weeks ago I noticed the engine was running a little rich. I have not rebuilt the carburetor yet, probably needs it. I took it out of the garage to drive it to work today. It idles and runs quit good when cold but after it has warmed up, about 4 or 5 miles, it acts like it does not want to idle and it runs a little rough. Could it just be the carburetor needing rebuilt or would it be something else?


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Re: Engine runing rough after warm

Post by Scoutpilot » Fri Aug 12, 2016 8:19 am

It could be as simple as a bad condenser or your distributor needs to be rebuilt. I suspect the problem is electrical. Check all of your ignition wires for proper tightness on clean connections.
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Re: Engine runing rough after warm

Post by tnspd » Fri Aug 12, 2016 8:37 am

All the plug wires are tight so not that. The points look fine and the gap is correct. How do I check the condenser?

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Re: Engine runing rough after warm

Post by Scoutpilot » Fri Aug 12, 2016 9:21 am

Do you have a spare or two?
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'71-72 CHARLIE TROOP,
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LOW LEVEL HELL.
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'48 B1PW126
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Re: Engine runing rough after warm

Post by skyjeep50 » Sat Aug 13, 2016 4:14 am

Could also be the coil - heat can cause them to fail. Are the vent lines to your distributor hooked up on your jeep? If you are looking for technical and troubleshooting guides, log into the Willys M Jeep site, www.willysmjeeps.com and you will find manuals, technical photos and much more in the "Downloads" section.

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Re: Engine runing rough after warm

Post by tnspd » Sat Aug 13, 2016 5:50 am

I took each plug out and they were pretty dirty, black color but dry, I cleaned them off with a wire brush and put them back in. The jeep ran fine for a day. Now it runs rough again. I think it is the carb. I do not have any spare parts at all so I will try to rebuild the carb first. I noticed the carb has fuel seeping around most of the gaskets.

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Re: Engine runing rough after warm

Post by tnspd » Sat Aug 13, 2016 5:52 am

I have a more immediate oil leak I need to address. The hose running from the oil filter to the drivers side of the block is leaking from behind the fuel pump. Maybe the line has a fray in it and started leaking.

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Re: Engine runing rough after warm

Post by Scoutpilot » Sat Aug 13, 2016 6:02 am

From your description it sounds like the carb is flooding. Make sure of your float setting, metering rod setting and that the heat riser works correctly. Stuck open, the exhaust will heat the carb to the point where fuel boils, pressurizes the bowl and is forced past the metering rod jet.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

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Re: Engine runing rough after warm

Post by Joe Gopan » Sat Aug 13, 2016 9:46 am

Have you considered that the rubber diaphragms may have exceeded their service life and are deteriorated? That would be my initial thought.
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Re: Engine runing rough after warm

Post by tnspd » Mon Aug 15, 2016 7:54 am

I ordered all the parts to tune up the Jeep and rebuild the CARB. I am having a new oil line made for the oil filter. I will report back once I get all the parts in and put on. I also ordered a timing light adapter since I need one anyway.

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Re: Engine runing rough after warm

Post by 4X4M38 » Mon Aug 15, 2016 5:04 pm

Might also check the distributor for a hairline crack.

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Re: Engine runing rough after warm

Post by tnspd » Sun Aug 21, 2016 1:14 pm

Well I got the jeep running pretty good now. I rebuilt the carb, plugs, points, and condenser. Went on a 15 mile drive and it has good pickup and runs well. Replaced the leaking oil filter line. I was going to set the timing but my pulley has no mark on it. What do you do to set the timing when the pulley has no mark to use to adjust the timing?

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Re: Engine runing rough after warm

Post by Scoutpilot » Sun Aug 21, 2016 1:24 pm

It’s very easy, if you have an accessible intake vacuum source, a vacuum gauge and a dwell/tachometer. Simply follow the instructions in this link http://oldjeepcarbs.freeforums.net/thre ... ming-light
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

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Re: Engine runing rough after warm

Post by tnspd » Sun Aug 21, 2016 2:08 pm

I have a vacuum gauge I use to use on my 37 International pickup but I do not have a tach and dwell 24v and the adapter to hook it up to the distributor.

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Re: Engine runing rough after warm

Post by artificer » Sun Aug 21, 2016 7:18 pm

tnspd wrote:I have a vacuum gauge I use to use on my 37 International pickup but I do not have a tach and dwell 24v and the adapter to hook it up to the distributor.
All you need is an auto multimeter from HF <$20. An essential tool for any hobbyist & tradesman just like the vacuum gauge. Setting points with feelers & best sounding RPM will get you by though.
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