Posted: Thu Oct 27, 2016 7:15 pm Post subject: 1954 M38a1 ignition problems. Spark plugs not sparking
Hey guys. I have been trying to start my jeep with no luck. I just finished restoring it and for some reason the spark plugs won't spark while I'm cranking the engine even when the ignition switch it on. I checked to make sure the points open, I made sure there wasn't a short out from the coil to the distributor, I cleaned the spark plug. I'm 15 so that's about all I know to do.
I hear the 24v coils last a long time so I shouldn't need a new one of those, and the spark plugs should be fine. Let me know if you can help. Thanks
BEN
Even if the timing is wrong the plugs will still spark. You said 24 V coil so I'll assume your jeep is stock ignition M38A1.
How did you verify the plugs were not sparking? Did you remove all four and screw them back onto their shielded leads and crank the engine while observing the plug's electrodes for spark? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Yes my jeep is stock, using the original wiring harness. I removed the number 1 plug and rested it on the exhaust manifold while cranking the engine. My dad watched to see if it sparked and it didn't.
Has the distributor been worked on or removed and re-installed recently?
Was the engine rebuilt just before this issue arose?
To troubleshoot a problem like this you have two ways to go.
1-A proper well documented & organized troubleshooting process using a published guide. This program will take you step by step in an organized process of elimination.
2-Shotgun troubleshooting which takes an odd, dis-organized approach like blind stabs in the dark and is often associated with innocent attempts by members to offer suggestions on web sites then you blindly follow each one in no particular order.
So I suggest you use system # 1 and start by opening your M38A1 service manual TM 9-8014 to the troubleshooting section on page 79, read the introduction then move on to page 84 , Para. 84 Ignition system.
To get you started I have an Illustration of those two pages combined into a simple organized troubleshooting process. You start with item 1 and stay in order and write the result of each test in the blank area to the right.
Ok, I changed the points and ended up with spark, I tried it. The engine fired a couple times but it was in the exhaust, so I guess the distributor is in the wrong place. Anyone know which way to turn the distributor to make it work?
Yes the distributor was taken out while I cleaned up and painted the engine. The engine was running before this a few years ago, no it has not been rebuilt
Joined: May 14, 2009 Posts: 971 Location: South Dakota
Posted: Sat Oct 29, 2016 4:51 am Post subject:
To backfire in the exhaust, it's firing the spark plug with a open exhaust valve. Timing is off. If you did not remove the oil pump, then the timing is still in place for the distributor since it only fits the drive one way. The shaft drive of the distributor is offset. You can rotate the distributor on it's base plate in a arc. If you have not moved this adjustment, then I think you have the spark plug wires in the wrong orientation. I would pull the spark plugs out, rotate the engine clockwise looking at the front of the engine, standing at the front bumper. Put your finger in the front #1 hole and rotate until you feel compression pushing your finger up and out of the hole. When it quits, you are at TDC on compression. Have the distributor cap off. See which way the rotor is turning while you rotate the engine. When you feel that you are at TDC on # 1, the rotor will point to the # 1 wire. Then arrange the wires 1,3,4,2. You will have the firing order back in the right position.
Thanks! The manual had the spark plug wires hooked in 2 different locations for the same order. I had the wrong order. I switched them and it is during correctly I just have to spend a little more time on it to make it perfect
Had you looked thru my ignition timing photo album carefully you would have came across this photo I put in there several years ago about the incorrect wiring arrangement in the TM 9-8014.
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