HELP!! M38A1 Timing

Bugler · Post by **Bugler** » Sat Apr 12, 2014 8:29 am

I need some help trying to get the timing on my 1952 M38A1, the engine was a rebuild from Willys Jeep Parts and the darn thing will try and start but it just mist gas and backfires out of carb. Is there any pictures of where the spark plug wires go where #1 on cap is at and the rest of them. Please need this to run before parade. Veterans are counting on her.

RICKG · Post by **RICKG** » Sat Apr 12, 2014 9:34 am

Post by **wesk** » Sat Apr 12, 2014 9:56 am

Is this a rebuilt engine that you installed and have not been able to get running at all? Or is this a rebuilt engine you installed, it ran a while and now won't run? Is this a stock 24 volt waterproof ignition A1 engine?

I ask because if the first & third question is a yes then it is very probable the basic timing steps were not followed at assembly.

1-With #1 cylinder TDC on compression the oil pump is installed and indexed per the manual. This step is necessary because the oil pump is driven by the cam and the oil pump drives the distributor. Improper indexing of the oil pump can result in the inability to swing the distributor body enough to set timing correctly.

2-Now the distributor is installed and the rotor should point towards the position of the #1 spark plug wire terminal. Caution here because the M38A1 TM 9-8014 Fig 79 shows the wrong wire positioning. It was corrected with a publication change a while later but most manuals we have did not come with the 7 changes that were issued against them.

The yellow numbers ID the correct routing of the wires.

3-With the points on the high point of the cam adjust them to an opening of 0.020. Now set the crank to it's 5 deg BTDC mark. Now you adjust the rotation of the distributor body so the points just start to open. Now looking at the 2nd photo below rotate the housing slightly towards retar until the points are closed. Slip a piece of paper between the contacts and maintain a slight pull on the paper and then very slowly rotate the distributor housing towards advance. The instant the piece of peper comes loose stop and tighten the housing retention bolt.

You may have one of several different timing mark arrangements.

Bugler · Post by **Bugler** » Sat Apr 12, 2014 1:29 pm

It comes from Willys Jeep Parts I got it for 2000.00. I installed everything is on it and it is a 24 volt waterproof system. I had it going for a minute it spit sputtered and back fired from card. I new the timing was off and I tried everything the get the timing right. the only thing I haven't done is take the oil pump off to check it. I am trying everything and just about ready to scrap the whole thing. I have spent about 8000.00 on this jeep so the guys in DAV could have a ride in parades and funerals but I am hurting and just can't do this thing if it don't work.

Post by **wesk** » Sat Apr 12, 2014 1:48 pm

I suggest you first take a step back and then when ready take an organized and well thought out approach. I can help with the organized approach a bit. Who installed the oil pump and distributor?

Bugler · Post by **Bugler** » Sat Apr 12, 2014 2:32 pm

The oil pump came installed in the engine when I bought it. The distributor I had that, came with the jeep. Should I pull the pump from the side where the exhaust is at and see if marks are lined up or take the front cover off to check the timing marks on the gears?

Bugler · Post by **Bugler** » Sat Apr 12, 2014 3:24 pm

I have a 24 volt distrib and it has no points it looks to be electronic.

Post by **wesk** » Sat Apr 12, 2014 6:18 pm

Put #1 TDC on compression. Use a measuring device IE dial indicator to assure absolute TDC since there's a overcenter effect that gives the crank a few degrees movement with no change in piston height. Your dial indicator will alert you when up movement stops then mark the crack pulley with a crayon and then continue til the dial indicator alerts you that down movement starts. Make a second mark. Split the difference for exact TDC.

Now view the pump's shaft position compared with the illustration. If not then remove and re-install it correctly.

If you have electronic ignition then just get the distributor with #1 indicated by rotor position with the crank rotated from TDC the short distance to 5 Deg BTDC. Hook up a timing light and start the engine. You may have to rotate the distributor housing a wee bit in either direction to help the engine start. Then set it to about 8 deg's BTDC to take advantage of the modern gas octane rating.

Bugler · Post by **Bugler** » Sat Apr 12, 2014 10:56 pm

I took the front cover off and made sure the timing gears where lined up with each other and my timing mark on my wheel is a hole in back that it lines up with not the notch on the wheel. The distrib hole looks like 11:00 if I can still tell time without a digital watch. I just need to check my oil pump line up and if its lined up right I guess I am good to go. have pics of what it looks like but can't figure how to put them on here.[/img]http://m38a1-1952.com/timing/1.jpg

Bugler · Post by **Bugler** » Sat Apr 12, 2014 11:01 pm

oops, didn't work out. darn pics.

Bugler · Post by **Bugler** » Sat Apr 12, 2014 11:27 pm

My jeep has 24 volt everything and I can't use a timing light on it because of the plug wires being military. I just know if I could send you the pictures it would show you what I have and that the timing marks on the gears at aligned with each other and the shaft for the distrib is at 1100. If you would like to give me a holler call 530-762-0056 as for wayne

Post by **wesk** » Sun Apr 13, 2014 1:21 am

Here's your own photo album here on our web site:
http://www.willysmjeeps.com/v2/modules. ... _album.php

Here's a short tutorial on how to load photos to it:
http://www.willysmjeeps.com/v2/modules. ... _album.php

#1 plug wire belongs at 7 o'clock.

The gear timing marks can line up at top on Exhaust and top on compression. You must remove all four spark plugs. Hold your finger over #1 and rotate the engine until you feel air pressure blowing your finger out of #1 hole. Now slowly continue bringing the piston up to TDC while watching the two gear marks. Now with the two timing marks on the cam and crank gears aligned and #1 top on compression the oil pump drive shaft should appear just like the right side of this photo.

The timing mark location you describe is not understandable. The M38A1 and M170 F134 engines all had the timing marks on the front cover and the lower crankshaft pulley. The old L134 flathead had the timing mark on the flywheel with a hole in the bell housing front plate to see the mark.

skyjeep50 · Post by **skyjeep50** » Sun Apr 13, 2014 9:17 am

You can use a standard timing light on the 24 v system if you have a timing light adaptor. You can get an entire electrical adapter test kit that includes the spark plug adapter (look on ebay) or the spark plug adapter is available from suppliers.
http://www.midwestmilitary.net/m38a1p11.html

Post by **wesk** » Sun Apr 13, 2014 9:54 am

Or, if you insist on working and repairing a jeep with 24 volt water proof electrics without the correct adapter set you can remove #1 shielded plug wire from both the cap and the plug. Then install a standard plug wire in the cap and on a (Champion) J8 or J8C or (AC) 45 or (Autolite) 295 spark plug that you installed in #1 plug hole..

Bugler · Post by **Bugler** » Sun Apr 13, 2014 11:16 am

I'll give the regular way of timing with a regular plug and wire. Thanks Wes I'll let you know what happens. I am scared to do anything with it since the timing gears dots are lined up and the oil pump is lined up, I don't want to turn it over and lose my marks, but I'll give it a try.