M38A1 crank but not starting

giacomo · Post by **giacomo** » Sat Jun 25, 2022 2:37 am

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

Giacomo

cobra5 · Post by **cobra5** » Sat Jun 25, 2022 6:28 am

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.

giacomo · Post by **giacomo** » Sat Jun 25, 2022 8:23 am

yes it worked regularly before, and I already cleaned the contacts on the breaker points....
thank you

Giacomo

RonD2 · Post by **RonD2** » Sat Jun 25, 2022 8:53 am

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!

giacomo · Post by **giacomo** » Sat Jun 25, 2022 11:13 am

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

Giacomo

cobra5 · Post by **cobra5** » Sat Jun 25, 2022 2:21 pm

The other thing that will prevent you from getting spark is the ignition switch

giacomo · Post by **giacomo** » Sat Jun 25, 2022 2:48 pm

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

Giacomo

cobra5 · Post by **cobra5** » Sat Jun 25, 2022 3:16 pm

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?

BBDE · Post by **BBDE** » Sun Jun 26, 2022 12:30 pm

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.

Frank

Good luck

giacomo · Post by **giacomo** » Thu Dec 08, 2022 7:19 am

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

Giacomo

RonD2 · Post by **RonD2** » Thu Dec 08, 2022 9:33 am

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!

giacomo · Post by **giacomo** » Thu Dec 08, 2022 12:08 pm

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 ?

batteries fully charged

I've actually never fixed it....

thank you
Giacomo

RonD2 · Post by **RonD2** » Thu Dec 08, 2022 12:50 pm

Giacomo,
If you search "coil test" using the search button above you'll get lots of information, including this one: http://willysmjeeps.com/v2/modules.php? ... =coil+test

Good luck!

Post by **wesk** » Thu Dec 08, 2022 9:33 pm

You may also want to review this post as well: http://www.willysmjeeps.com/v2/modules. ... pic&t=5652

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.

Also in my photo album Titled: Ignition Systems L & F 134 engines. http://www.willysmjeeps.com/v2/modules. ... _album.php, in sub-album titled Distributor: http://www.willysmjeeps.com/v2/modules. ... _album.php
You will also find a complete PrestoLite/Autolite test sheet set:

There are several pages of advance curves just download the one that applies to your specific part number distributor.

giacomo · Post by **giacomo** » Fri Dec 09, 2022 10:46 am

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

Giacomo