M38A1 smoking

Goodvet · Post by **Goodvet** » Sun Sep 13, 2020 7:44 pm

Hi, I've got a 1953 M38A1 CDN that I recently purchased and had not run much as we were repairing brakes. Started up today and it is pulling oil hard into the engine and burning it (blue smoke everywhere). We did a compression test and it is 120 psi on all four cylinders. We disconnected a metal vacuum line that originates by the intake on the passengers side and seems to go ahead and down under to the fuel pump/vacuum system on the drivers side. When we disconnect this pipe, everything is fine. What is happening? We were wondering if a diaphragm or something has blown on that fuel pump? Any ideas or technical data on how that works would be appreciated!

Post by **wesk** » Sun Sep 13, 2020 10:36 pm

Since you did have a compression gauge I would suspect you have or have access to a fuel/vacuum pressure gauge. Then complete the gauge tests that need to be done to help you choose a path down thru the troubleshooting section of TM 9-8014.

You did not tell us a lot about the current configuration of the fuel, vacuum, vent and fording systems. What you have and how it is setup has a huge impact on where the source of your oil is coming from.

Goodvet · Post by **Goodvet** » Mon Sep 14, 2020 8:04 pm

Where would I find this troubleshooting section? Is there a copy online here somewhere. I'll try to get the other information.

Post by **wesk** » Mon Sep 14, 2020 8:47 pm

It is often assumed that every M38 owner has the military version of an owner's manual on his bench. It is called TM 9-8012. If you don't have a copy just go to our "Downloads" page and download your free PDF copy or go on line and buy a copy. The other 3 books you should also keep at your bench are TM 9-1804A Eng/Clutch, TM 9-1804B Chassis & running gear and ORD 9 SNL G-758 the parts manual. Again they are all free to download right here on this web site on our downloads page in PDF format. Other helpful manuals are The civvy SM1002 which covers the CJ2A/CJ3A which although 6 or 12 volt still run the L134 engine. Most of the important chapters of SM1002 are free for you download from my photo album.

The Army used several manufacturer specific manuals to cover more accessories in better detail. They were specialized manuals devoted to a single manufacturer Lik this one for our jeep's steering gear sets.

Eades · Post by **Eades** » Tue Sep 15, 2020 11:11 am

I am currently having the same issue on a recent pump rebuild. After 500 miles it started smoking. I tracked it down to the vacuum pump that I installed the oil seal backwards allowing oil into the vac pump and subsequently pumping it into the intake.

Could be the oil seal or you have a hole in diaphram.