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willysmjeeps.com :: View topic - Engine M38A1 doesn't run well...
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Engine M38A1 doesn't run well...

 
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willems
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Joined: Jul 08, 2018
Posts: 3
Location: Belgium

PostPosted: Mon Jul 09, 2018 2:54 am    Post subject: Engine M38A1 doesn't run well... Reply with quote

Hello

A month ago i bought an M38A1 Nekaf jeep. Since the start the engine was running badly. Stationary engine start and stationary turning, the engine handles well. Once on the road, the engine shakes an makes small exhaust explosion sounds. It's like the engine is running on three cilinders instead of four. While taking the exhaust manifold apart, i noticed that the exhaust of cilinder no. 1 was wet, while the other three burned good. Could this be an carb problem or an ignition OR ignition time problem?

What I did so far:
-Carb completely revised with set
-Fuel pump revised with set
-compression test OK
-installed new plugs and plug wires
-exchanged everything in the waterproof auto light distribution system (coil, inside distribution cap, breaker point, condensator,
Please Help Embarassed
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LTDan
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Joined: Oct 13, 2017
Posts: 28

PostPosted: Mon Jul 09, 2018 7:55 am    Post subject: Reply with quote

Sounds like you have either a ignition problem or a timing problem. The carb flooding is also a possibility but not likely.

Check that you are getting spark to the No 1 plug.
It should be hot and blue

If your not getting spark then remove the no 1 plug wire and use a wire or screw driver in the distributor to see if you get spark to the engine block or ground. Use something well insulated to hold the wire or screwdriver. as you don't want a shock.

Check the plug wire for any breaks or open insulation. If the spark is jumping to the block through the insulation then you are not getting fire to the plug.

Check that your plug wires are going to the proper cylinder.

Check the timing. If you do not know how to do this then take it to a mechanic shop, one that has been around for a long time and has experience working with carbuerated engines.

Don't over look the carb having trash in it. clean the float needle and seat. Check that the float lvl is at the proper setting.
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wesk
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Joined: Apr 04, 2005
Posts: 13567
Location: Wisconsin

PostPosted: Mon Jul 09, 2018 8:45 am    Post subject: Reply with quote

Quote:
i noticed that the exhaust of cilinder no. 1 was wet, while the other three burned good.


We will need a better description of wet before we can offer solid advice. Wet with Fuel, Oil or Coolant???

One wet plug or exhaust port with gas does not point to a flooding carb. It points to either an ignition issue on #1 or a valve issue on #1.

A very good starting point right now is a Compression test & leak down test.
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45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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willems
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Joined: Jul 08, 2018
Posts: 3
Location: Belgium

PostPosted: Wed Jul 11, 2018 12:09 pm    Post subject: Reply with quote

Thank LTDan & Wesk for you reply.

I've done a compression test again on all four cilinders, with following results: 110 psi on all four cilinders. This should be normal? All plugs are sparking and I did a timing test with a timing light. Now it should be correct. What I noticed, is that all the sparks are blackened afterwards (soot)? The problem persists: the engine flutters when driving and accelerating. Exhaust gasses are black - blue and are smelling heavy. Engine starts immediately and runs good when stationary. The new sparks are the Bosch-type ones with two electrodes. Couldn't it be a carb problem though?

thanks in advance!
From a new member. Very Happy
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mdainsd
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Joined: Oct 20, 2017
Posts: 155

PostPosted: Wed Jul 11, 2018 12:33 pm    Post subject: Reply with quote

Blackened spark plugs and black exhaust smoke leads me to believe you have a carburetor issue. Way too rich from the sound of things. That is carburetor based.

Blue smoke is an indicator of burning engine oil. This can be a oil control ring issue or intake valve seal failure (I assume with overhead intake valves Willy's thought to put in valve stem seals).

As Wes said it would really help if:

1) You can identify what is wetting number one's spark plug; fuel, oil or coolant.

2) Do the requested leak down test.

Id add one more, a wet compression test. with that much overfilling going on there is a good chance the fuel is washing the oil off of the cylinder walls causing the lower compression. Pul the dip stick, does the oil smell of gasoline?

Im thinking you have two problems at once.
_________________
2004 M1025, 1952 Dodge M37, 1968 Dodge M615 export ambulance, 1942 MB script, 1948 FrankenJeep CJ2A/M38, 1951 M38, (2) M1941 Sperry 60" Anti-Aircraft Searchlight, (3) John Deere M-gators.
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willems
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Joined: Jul 08, 2018
Posts: 3
Location: Belgium

PostPosted: Wed Jul 11, 2018 12:57 pm    Post subject: Reply with quote

Thank LTDan & Wesk for you reply.

I've done a compression test again on all four cilinders, with following results: 110 psi on all four cilinders. This should be normal? All plugs are sparking and I did a timing test with a timing light. Now it should be correct. What I noticed, is that all the sparks are blackened afterwards (soot)? The problem persists: the engine flutters when driving and accelerating. Exhaust gasses are black and are smelling heavy. Engine starts immediately and runs good when stationary. The new sparks are the Bosch-type ones with two electrodes. Couldn't it be a carb problem though?

thanks in advance!
From a new member. Very Happy
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STXM38A1
Member


Joined: Jul 25, 2009
Posts: 129
Location: Fair Oaks Ranch, Texas

PostPosted: Wed Jul 11, 2018 4:02 pm    Post subject: Reply with quote

A shot in the dark, but hasn't been mentioned...
The ole spark plug wire switch-a-roo


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M38A1 12/54 MD 78343

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