M38A1 Lost of power

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
Post Reply
CARBERAME
G-Corporal
G-Corporal
Posts: 23
Joined: Tue Aug 05, 2014 10:02 am
Location:

M38A1 Lost of power

Post by CARBERAME » Thu Sep 25, 2014 9:41 am

For the last 20 years I’ve been enjoying with full satisfaction my M38A1. The engine has been running with plenty of power and smoothly all the time.

Last year I restored the car and took the engine out of the body and, when finished, installed it again without doing anything at all to the engine, other than cleaning it.

Since then it has lost a lot of power. When it has to climb even a small rise or uphill the engine chokes and loses strength. If then I pull the choke or take out the air filter tube, it seems to recover a bit or even use the low transfer..

I tried changing the carburator for a rebuilt and checked one; the air filtre is clean; the firing duly on time; the brakes work fine. As I changed the whole fuel lines, I thought that may be the fuel was not driving enough flow to the carburator; so I put a can directly to it. The compressions are OK, too.

I don’t know what else can I do to recover the power and strength.

Can any one give me an idea to solve this problem?


Joe Gopan
Jeep Heaven
Posts: 49841
Joined: Sun Mar 02, 2008 12:37 pm
Location: Proving Ground

Re: M38A1 Lost of power

Post by Joe Gopan » Thu Sep 25, 2014 9:51 am

Check for a kinked fuel pump hose, and that the shut of valve for the fuel line is open. Go back and check the fuel line connections between the tank and pump. If you have access to a vacuum gauge, see if you can rig up a fitting to install a vacuum gauge to at the fuel pump inlet. Give the Carburetor a rap at the fuel line elbow with a plastic hammer, and check the screen inside the fuel line inlet fitting at the carburetor. Check the choke cable to see if it allows the choke to open, and check your throttle linkage for full travel.
Next check your point setting for 0.020" Do this first as it is a quick task.
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

Dave M38A1
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 442
Joined: Mon Mar 23, 2009 4:28 pm
Location: Fuquay-Varina, NC

Re: M38A1 Lost of power

Post by Dave M38A1 » Thu Sep 25, 2014 10:43 am

When my vacuum advance weights in the distributor were stuck on my CJ, it didn't have any power, (ran but wouldn't pull) something to check. They were also stuck on the M38A1 also but a hole in one piston. stuck rings, bad valve seats, pumping oil out the exhaust proved, it needed re-builing, but it was good to hear it run. Waiting on time to assemble the parts I've collected in the machined block to get it running again.

Dave
Dave M38A1
1953 M38A1
1964 USMC M38A1
M274 A5 Mule (Pepe')
64 CJ5
97 TJ Wrangler (Son's Ride)

Marty, SoCal
G-Lieutenant General
G-Lieutenant General
Posts: 6319
Joined: Thu Mar 09, 2006 10:34 am
Location:

Re: M38A1 Lost of power

Post by Marty, SoCal » Thu Sep 25, 2014 11:32 am

Since you R&R'd the engine, and there are alot of throttle links that could have been misadjusted on the M38-A1, the first thing I would check is that you are still getting full throttle at the carb!

Have a buddy push the gas pedal all the way to the floor and check that the carb is opening wide. You may need to release the connection at the throttle lever on the carb to make sure it's actually going wide open.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license

Joe Gopan
Jeep Heaven
Posts: 49841
Joined: Sun Mar 02, 2008 12:37 pm
Location: Proving Ground

Re: M38A1 Lost of power

Post by Joe Gopan » Thu Sep 25, 2014 2:19 pm

Only adjustment is at the bell crank at the stud at the valve cover, I have never seen it done but is it installed wrong side to on the stud?
Can you post a pic of your linkage?
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

CARBERAME
G-Corporal
G-Corporal
Posts: 23
Joined: Tue Aug 05, 2014 10:02 am
Location:

Re: M38A1 Lost of power

Post by CARBERAME » Mon Oct 06, 2014 7:12 am

Thank you all. Now I have a lot to do and try with your suggestions.
Here is the photo i guess Dover asks for
Attachments
IMG_1753.jpg
(201.3 KiB) Downloaded 615 times

Marty, SoCal
G-Lieutenant General
G-Lieutenant General
Posts: 6319
Joined: Thu Mar 09, 2006 10:34 am
Location:

Re: M38A1 Lost of power

Post by Marty, SoCal » Wed Oct 08, 2014 11:41 am

Ben wanted to see the carb throttle linkage. The posted picture is the crankcase vent shut-off valve for water fording.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license


Post Reply

Return to “M38a1 Technical Knowledge Base”

Who is online

Users browsing this forum: No registered users and 44 guests