Posted: Sat Jun 25, 2022 2:37 am Post subject: M38A1 crank but not starting
Hi all,
here I am with another problem
after two years in which the 1954 M38A1 has stood still, now it no starting
crank but not starting.....
the gasoline reaches the carburetor, but by disconnecting the spark plug cables and bringing them closer to the engine block at the moment of starting there are no sparks .....
primary capacitor - ignition coil or breaker point capacitor ...?
thank you
Joined: Mar 10, 2013 Posts: 105 Location: Stevensville, Montana
Posted: Sat Jun 25, 2022 6:28 am Post subject:
If it ran before you parked it, use a piece of sandpaper and clean the contacts on the breaker points and than check again for spark. _________________ 1951 M37 WOW, 1953 M37 WOW, 1954 M37 WOW, 1953 M38-A1, 1954 M38-A1, 1964 M151-A1, 1967 M151-A1, 1968 M151-A1, 1978 M151-A2, 1989 M35A2C, 1965 M416, 1966 M416, 1967 M416
MSgt, USAF Retired 1/84-10/05
Joined: Oct 02, 2014 Posts: 2010 Location: South Carolina, Dorchester County
Posted: Sat Jun 25, 2022 8:53 am Post subject:
Hi Giacomo,
You don't say if your M38A1 is original. Original carburetor? Never rebuilt? Original 24-volt electrical system?
It's hard enough to guess the problem from long distance sight unseen. Taking some photos and giving a description and history of your jeep would help.
Until then, I suggest begin by draining and flushing the old gasoline from everywhere (tank, lines, carb, pump). Buy some fresh fuel.
Then open the Army manual TM9-8014 that you downloaded for free and follow the steps in Section IV Troubleshooting that begin on page 79.
Good luck! _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Hi RonD2
M38A1 original with original carburetor rebuilt 3 years ago and original 24V electrical system
unloaded the old gasoline from the tank and filled with fresh fuel
thank you
I also did this test, I disconnected the electrical cable from the wiring harness receptacle and with ignition switch on and measured the voltage: 24V......
thank you
Joined: Mar 10, 2013 Posts: 105 Location: Stevensville, Montana
Posted: Sat Jun 25, 2022 3:16 pm Post subject:
Is the distributor rotor spinning when the engine is cranking? All connections clean and tight inside the distributor? Have you performed the ohms check on the coil yet? _________________ 1951 M37 WOW, 1953 M37 WOW, 1954 M37 WOW, 1953 M38-A1, 1954 M38-A1, 1964 M151-A1, 1967 M151-A1, 1968 M151-A1, 1978 M151-A2, 1989 M35A2C, 1965 M416, 1966 M416, 1967 M416
MSgt, USAF Retired 1/84-10/05
Joined: Mar 05, 2008 Posts: 78 Location: Berlin Germany
Posted: Sun Jun 26, 2022 12:30 pm Post subject:
If you don't have an ignition spark although there is 24 volts at the distributor and you have already cleaned the contacts, the distributor shaft rotates when you turn the engine, you have also already checked the distributor cap, fingers, cables and spark plugs, it may be the ignition coil is shot.
If the ignition has been switched on for a long time and the engine has not been running, the ignition coil may have been damaged.
The old originals are more short-circuit proof than, for example, the repro coils, but they also have their load limits.
In any case, you should proceed logically and systematically when troubleshooting and not try a little here and there.
a look at the manuals will definitely help you.
You will surely get the needed help and the necessary tips here in the forum.
Hi all,
the problem comes back : hard starting to cold engine
Could it be a bad coil ?
how is it measured ?
also how can I measure the speed of the starter to exclude it as the cause of a slow cranking speed ?
thank you
Joined: Oct 02, 2014 Posts: 2010 Location: South Carolina, Dorchester County
Posted: Thu Dec 08, 2022 9:33 am Post subject:
Hi Giacomo,
Did you check to see if you have bright blue spark across a spark plug gap when cranking the engine?
If yes, the coil isn't the problem.
Are your batteries fully charged?
You might test them (at battery shop) for full cranking amp capacity.
I believe some smart phones can measure RPM of a cranking engine.
Or you can buy a portable tachometer.
I believe the starter should crank the engine about 200 RPM.
You never told us --- what did you do to fix your last problem back in June?
Good luck! _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Hi Ron,
I still have to check bright blue spark across from the cable to the engine block ( new spark plugs ) but in any case how do you check the coil with the tester ?
Don't forget to do the test at room temp and then again after heating the coil up with a hair dryer or heat gun.
Also try to remember the Ohm meter checkout can be used with some reliability but the preferred method is with an actual coil tester that measures coil current draw.
There are several pages of advance curves just download the one that applies to your specific part number distributor. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Today I checked the coil with VOM digital test and the following results:
primary : 6,9 ohms
secondary ( between B and D ) :open ( no reading )
then i tested a second coil and the result is the same
could this be the cause of the increasingly difficult starts ?
and where can I buy a coil that is valid ... ?
thank you
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