carb problem

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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Gary Turman
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carb problem

Post by Gary Turman » Thu Apr 28, 2016 7:57 am

My jeep is running real rich. It smokes blue smoke. If I completely remove the air/fuel mixture screw it actually runs better. It is the original side draft ys. any ideas what might be my problem?
1941 Dodge WC-7 Command Car
1942 Ford GPW
1968 M151-A1
1967 M416
1945 Gemco 1/4 ton trailer
US Army 1979-1984
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muttguru
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Re: carb problem

Post by muttguru » Thu Apr 28, 2016 9:59 am

Has anyone been tampering with the Donaldson Valve (aka the PCV valve) ? A friend of mine was having similar problems and the cure was to correct the reassembly of the valve.
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Gary Turman
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Re: carb problem

Post by Gary Turman » Thu Apr 28, 2016 10:22 am

hasn't been messed with it but I will certainly check it out..thanks
1941 Dodge WC-7 Command Car
1942 Ford GPW
1968 M151-A1
1967 M416
1945 Gemco 1/4 ton trailer
US Army 1979-1984
Houston Police Officer 1984-2016 (Retired)

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Re: carb problem

Post by Joe Gopan » Thu Apr 28, 2016 10:36 am

The YS Series M-38 and M-38A1 series carburetors will run rich when the rubber diaphragms develop internal leaks due to the age of the rubber. How long has the present carburetor been installed?
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Gary Turman
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Re: carb problem

Post by Gary Turman » Thu Apr 28, 2016 10:43 am

I put a rebuild kit in it a couple of years ago. What should I look for on the PCV valve? I do remember taking it out and cleaning it. Can it be accidently installed backwards?
1941 Dodge WC-7 Command Car
1942 Ford GPW
1968 M151-A1
1967 M416
1945 Gemco 1/4 ton trailer
US Army 1979-1984
Houston Police Officer 1984-2016 (Retired)

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wingnut1
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Re: carb problem

Post by wingnut1 » Thu Apr 28, 2016 11:02 am

Hi. It is possible to put the P.C.V. valve on the wrong way on a M38A1 because it has male threads at both ends. However there should be an arrow stamped on to show the direction of flow towards the inlet. Hope this helps you as it did for me. Best regards Bernard.
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Re: carb problem

Post by artificer » Thu Apr 28, 2016 11:41 am

Joel is probably on the money.
The vehicle is said to be running rich.
Removing the idle mixture screw is said to cause the engine to run better.
That is because removing the mixture screw introduces air into the idle circuit, leaning the mixture.
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Re: carb problem

Post by Fabrizio » Thu Apr 28, 2016 1:43 pm

Wouldn't rich mixture cause black smoke, and not blue?
Blue sounds more oil related, be it pcv, rings, or valve guides
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Re: carb problem

Post by artificer » Thu Apr 28, 2016 1:56 pm

Petrol/gasoline engine blue /black is harder to distinguish v/s a diesel engine.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: carb problem

Post by Joe Gopan » Thu Apr 28, 2016 2:42 pm

If the excess gas is getting into the base the diluted oil will wash by guides, Rings, guides, etc., and the exhaust can exhibit blue smoke.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO


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