F-134 (M-38A1) Timing Issue

OKCM38CDN · Post by **OKCM38CDN** » Mon Apr 26, 2021 5:31 pm

I took my recently alive M-38A1 out to see how it drove, backfiring thru carb (Minor) and no real power. So I took it home and decided I would run a timing light on it to see if that would improve things.

The Distributor is all the way Counter clockwise as far as I can get it (It is bumping against the Generator). So I pulled the distributor and looked at the orientation on the oil pump. It looks good as far as I can tell. I have plenty of adjustment clockwise (Toward the rear block), just none Counter.

I am thinking that the oil pump may be off one tooth. So I am thinking of pulling the pump and spinning it one tooth over. This theoretically should give me a bigger range of adjustment...

Thoughts please, supposed to rain tomorrow so got a few days to think this over...

Post by **wesk** » Mon Apr 26, 2021 6:35 pm

The index illustration for the top of the oil pump drive is based on a very precise placement of #1 cyl TDC with the two "0" marks on the cam gear and crank gear perfectly aligned. The only way to assure you are in the correct place with the pump gear shaft is with the timing cover removed to confirm the placement of the two "0" 's on the cam gear and crank gear. This is very clearly spelled out in TM 9-8015-1, page 115, para 101.

What you are trying to do is to assume someone set the cam gear to crank gear correctly and just got the oil pump clocked wrong during it's installation. You may get lucky and get your ignition timing adjustment closer to correct but your basic valve timing may still be in error.

Eades · Post by **Eades** » Mon Apr 26, 2021 7:21 pm

The oil pump could be off a tooth. My personal experience was when my engine was rebuilt and reassembled the pump was installed 180 degrees off. It had never ran. I finally figured that out when pulling my hair out trying to start it and properly clocked it. I then had the same issue you described with only being able to adjust distributor one way. I pulled the oil pump again and bumped it over one tooth and all is well now. I am able to advance or retard the timing now.

RonD2 · Post by **RonD2** » Mon Apr 26, 2021 9:29 pm

Hi Hal,
Without comparing both M38 and M38A1 manuals that both tell how to correctly assemble the motor ----- isn't clocking the oil pump, distributor, and timing gears exactly the same for both the F134 and the L134 motors?

You have both motors? Assuming your M38 is up and running good ---- it ought to be fairly easy to get the F134 straightened out?

Plenty of old posts about it, including this one: http://willysmjeeps.com/v2/modules.php? ... t=oil+pump

Double check your spark plug wires for the correct firing order....

Good luck!

Post by **wesk** » Mon Apr 26, 2021 9:49 pm

I could be mistaken, but isn't correctly clocking the oil pump, distributor, and timing gears exactly the same for both the F134 and the L134 motors?

That is correct!

Hal, Just for the heckuvit post a photo of the plug wire arrangement in your distributor cap. I ask because the M38A1 service manual has an incorrect wire arrangement that was corrected by two separate changes but these changes never seem to be in the manual copy on hand.

Incorrect illustration

Corrected illustration

OKCM38CDN · Post by **OKCM38CDN** » Tue Apr 27, 2021 7:08 am

I know #1 Plug is in the Lower left position, I will double check the rest just to be sure. (Edit - Just checked the rest, #2 and #3 were swapped it is now set to 1,2,4,3 going in a CCW direction).

The photo I posted is my current position of the oil pump.

As for the timing gears on the crank and cam, I set those long ago as I know how important they are.

I learned a lot on my M-38CDN, and this one went a lot better, but just cannot get any adjustment on the distributor...

Will continue later today have appointments this AM...[/b]

OKCM38CDN · Post by **OKCM38CDN** » Wed Apr 28, 2021 3:54 pm

Went back thru everything and made sure the plug wires were NOT crossed and put it all back together.

It fired up with ease and is running like a top... took it for a drive around the block and it has lots of POWER...

So motor is good, Looking at a fuel leak (possible bad fitting or crimp) and a leaky Master cylinder (New one in hand).

Raining hard today so will have to wait for rain to stop.

One step forward...

RonD2 · Post by **RonD2** » Wed Apr 28, 2021 4:13 pm

Glad to hear it Hal!

So the problem wasn't the distributor mis-clocked to the oil pump --- it was bad firing order?

Your distributor now has plenty of adjustment range?

RonD2 · Post by **RonD2** » Fri Apr 30, 2021 8:06 pm

Guess we'll have to keep wondering.......

OKCM38CDN · Post by **OKCM38CDN** » Fri Apr 30, 2021 10:44 pm

Sorry, been busy I have a reasonable adjustment range now, Power connector is about 1.5 inches from the generator and plenty of room to go the other way.

Was under the jeep today and reformed the ends of the fuel lines. Making sure the flares were straight and able to seal properly.

Ran out of time so will test run it tomorrow to see if it leaks...