BREAKING UP
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- G-First Lieutenant
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BREAKING UP
My M38 has been running really good all summer. A few weeks ago, she started to hesistate, misfire, around 10 Mph. Now, if you floor it in 1 st gear, there is no power and stumbles something terrible, around 10 to 15 MPH. She idles ok and starts right up. Per the manual, I cleaned plugs and even changed them with some old ones I had and no difference. I did change out the points and condenser as they were cheap. Cap and rotor look good. I think it may be the coil? I do have an extra but I thought would ask here. Thanks John
- dpcd67
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Re: BREAKING UP
It is usually fuel when that happens, but do your troubleshooting steps to isolate it. But I have had that happen and it was clogged fuel filter. Check float and bowl too. When the carb needs fuel, it is starved.
U. S. Army 28 years.
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Re: BREAKING UP
Your Carburetor may need a Kit, The Pump Diaphragm may have ruptured due to age and reaction of the rubber diaphragm to today's fuel. It's a common event in the YS M-Series Jeep Carburetors. They age and rupture, more so now with today's fuel.
All Jeeps with YS Carburetor can expect this.
All Jeeps with YS Carburetor can expect this.
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- G-First Lieutenant
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Re: BREAKING UP
Ok, this may explain why I cannot adjust the idle air mixture and why I get this unwanted rpm increase, if that makes sense. There are no vaccumm leaks as I checked and the fuel filter in the tank is newer. I will change that coil out just to see but my bet is on your answer. I will let you know and Thanks, John
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- Sergeant Major of the Gee
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Re: BREAKING UP
And avoid Ethynol gas. It will create moisture in the tank and wreak havoc with the running. Try also, draining the tank and put in a fresh tank of non-ethynol gas. Might save you some $$$$.
FrankenJeep
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Re: BREAKING UP
If you have never worked on the YS before, be careful not to tip the float chamber upside down, that little rectangular brass weight that just fell out had a check ball under it.
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
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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
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- G-First Lieutenant
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Re: BREAKING UP
Got hime from work and replaced the coil with spare I had and that was not the problem. I pulled the carb just now and I am sending back to the vendor I purchased from just over a year. He is very nice enough to look it over for me to see what's up as it is close to the warranty period. I will make a note of that ehthynol issue. I will get back to you. Thanks again for your help. John
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Re: BREAKING UP
Hello. Will 91 octane ethanol free fuel be ok in the m38? I found one station by me that sells this. Thanks. John
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Re: BREAKING UP
Won't hurt a thing.
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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
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Re: BREAKING UP
Today I installed the rebuilt carb for my M38 and it still has no power. She idles Ok but if you throttle up quarter of the way starts to break up and again no power. I changed everything in the distributor and the radio condenser also(that second condenser). I attached a hose to the fuel pump and it fills up rather quickly. I pulled the muffler and ran up the street, no difference. The manual states to run a compression test. I guess I will do that next to make sure that is ok. But, she ran fine all summer and does not use a drop of oil. The plugs looked OK when I pulled them out, even swapped in some spares, no difference. Coil aslo. I checked the timing and the I assume the advance springs are OK if you throttle up and the timinig marks move. Question: could a fuel pump be defective at higher rpms'? not pumping enough fuel. I have nothing in the tailpipe like fuel or anything.
Any ideas, besides the compression test to check the internals. Thanks John
Any ideas, besides the compression test to check the internals. Thanks John
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Re: BREAKING UP
Spark Plug wires, perhaps, these wires do fail at times Remember not to wrench them tight onto the spark plugs as it can roll over the threaded end of the spark plug creating a wire edge that will grip the orange insulation and cause it to pull apart. Mechanics learned to tighten these wires finger tight at the plugs as the Jeep was not going fording.
The owner made a video of the fault.
The owner made a video of the fault.
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
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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- G-First Lieutenant
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Re: BREAKING UP
Luckily I saved the old wires and will put them back on. The current wires were placed on a couple years ago. I remember you telling all of us not to tighten them too much, which I do not. I will replace them today and get back. Thank you, John
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Re: BREAKING UP
Ran out just now and swapped those wires, no difference. I can drive 5 mph and it is fine, step on the gas stumbles and bumbles and does not power up at all. Starts, Idles just fine and engine is quite. I am wondering if the fuel pump is the culprit under load. Would a bad coil cause this?
Both my coil are very old, maybe coincidence that they are just both bad. John
Both my coil are very old, maybe coincidence that they are just both bad. John
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Re: BREAKING UP
When you inspected the carburetor did you note if the Metering Rod Diaphragm had the spring with the finer wire? There is a light and heavy spring, heavy spring is the pump spring.
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
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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Re: BREAKING UP
Point gap closed up will cause this lack of acceleration power type issue.
This because the coil does not have time to saturate properly.
Points fitted dry with no lube on the rubbing block or cam will close up rapidly.
EZ to check & eliminate immediately by using a dwell meter. Nothing needs removing or disconnecting to do this check.
Think about what has been done changing parts incl. carb coil etc. None altered anything so it is something that hasen't been eliminated.
This because the coil does not have time to saturate properly.
Points fitted dry with no lube on the rubbing block or cam will close up rapidly.
EZ to check & eliminate immediately by using a dwell meter. Nothing needs removing or disconnecting to do this check.
Think about what has been done changing parts incl. carb coil etc. None altered anything so it is something that hasen't been eliminated.
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.
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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