Dead in the water

1950 - 1968, M38, M38A1, M170, modifications, sugestions, and ideas, official MWO's and unofficial field mods.
Mjfire1949
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Dead in the water

Post by Mjfire1949 » Wed Mar 19, 2014 2:48 pm

Second week of ownership of a M38. I was changinging the plugs this morning when I dropped a wrench that hit the starter terminals and caused it to arch. When I got ready to start it up, I had no electrical at all. Guages not even working. Do these have a fusebox? All connections are good including the ground cable. It was purring like a kitten prior to this issue. Any help would be sincerely appreciated. I have ordered a mechanics manual, but it hasn't arrived yet.


Joe Gopan
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Re: Dead in the water

Post by Joe Gopan » Wed Mar 19, 2014 2:52 pm

You may have fried the Starter switch.
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Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Wed Mar 19, 2014 5:54 pm

I was suspecting something "starter" since that's where the problem began. This switch would cause everything else to be dead? Its like the batteries are dead or the ground strap is loose. Thanks for the reply.

Warren Duchesne
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Re: Dead in the water

Post by Warren Duchesne » Wed Mar 19, 2014 6:32 pm

One side of the starter switch , the side with the lead that goes to the positive post should have power all the time . There should be a smaller cable attached at that same point that powers up the whole electrical system . If I remember correctly , thru the regulator .i wish I had my manual with me , I am out of town . It really should have not hurt the power to the rest of the system . It should have isolated the high resistance to the positive and negative battery cables and connections . Warren Duchesne

Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Wed Mar 19, 2014 7:05 pm

Thanks Warren. Sounds like I'll be trouble shooting tomorrow. Just learned the hard way to disconnect the batteries anytime I'm under the hood for anything other than fluid checks. 60-70 year old vehicles are a lot more sensitive to arching than I'm used to. Again, thanks for the reply.

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Re: Dead in the water

Post by Joe Gopan » Thu Mar 20, 2014 4:57 am

Smaller cable is #4 and goes thru the Voltage regulator. You may have cooked something. There is a Circuit Breaker inside the Generator Regulator, one behind the Instrument Panel for the instruments, and there are as many as three others, horn and Generator, Ignition Switch, and headlight switch. Some have one mounted on the battery box.
Your problem could be in the Generator regulator.
Do you have the early or late starter?
Early starter is mounted with two 3/8" Cap Screws (9/16" wrench) later has 1/2" Bolts (3/4" Wrench).
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

Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Fri Mar 21, 2014 8:02 pm

The vehicle has the late starter 3/4 bolts. The starter switch looked burned. I have ordered a new one. I wasn't showing any power at the switch. If not I'll look at the voltage regulator and the generator next. The army manual for M38 states that circuit breakers were installed on model numbers later than mine (65666). I'll keep you updated when I figure it out. Thanks for the replys.

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Re: Dead in the water

Post by Joe Gopan » Sat Mar 22, 2014 4:56 am

You can take the switch apart for a look, it will be obvious. Disconnect the batteries and remember where the wires on the switch go.
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

Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Tue Mar 25, 2014 7:54 pm

The problem was isolated to the voltage regulator.

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Re: Dead in the water

Post by Joe Gopan » Wed Mar 26, 2014 4:47 am

And do you have a replacement?
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

Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Wed Mar 26, 2014 5:41 pm

Yes. I ordered a NOS and have replaced it. I also took the starter switch off and cleaned it up. I now need to address the carbureator. Is it best to exchange for a rebuilt one. It has a lot of hesitation on acceleration and just crappy performance overall.

Joe Gopan
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Re: Dead in the water

Post by Joe Gopan » Wed Mar 26, 2014 5:54 pm

The Carburetor may just need a kit. There are two diaphragms that age and deteriorate after a few years, they will cause rich idle and hesitation.
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

Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Thu Mar 27, 2014 3:55 am

Thanks. I was back and forth about either a kit or complete exchange. I think I"ll try the kit first.

Joe Gopan
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Re: Dead in the water

Post by Joe Gopan » Thu Mar 27, 2014 6:03 am

When you have the top off, be careful, when you tip it up there will be a Weight, WO-116909, for the Pump Discharge Check Ball WO-116813. They will fall out onto your bench or go rolling on the floor. The weight is Brass and approx 1/8" X 3/8". Back in the days of pants cuffs, that's where many of them ended up. :wink:
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

Mjfire1949
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Re: Dead in the water

Post by Mjfire1949 » Thu Mar 27, 2014 2:59 pm

Thanks for the tip, Ben. Murphy's Law usually strikes when I attempt something like this. I might just send it in for an exchange.


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