M38a1 engine popping from exhaust, now backfiring and no start.

[Leigh H]

My m38a1 Engine is making a popping noise from the exhaust when the engine is running at idle , recently fitted rebuilt carb and Fuel pump , But I had the issue before the carb and fuel pump where fitted , any ideas what the problem would be thanks

 

[NDT]

Is it continuously or occasional? Occasionally they all do that.

 

[Leigh H]

Is it continuously or occasional? Occasionally they all do that.

Hi yes it is continuous??

 

[NDT]

Hi yes it is continuous??

I would start with a compression check. Sounds like valve problem.

 

[Leigh H]

Ok will start there many thanks

 

[Jbulach]

Is the truck new to you, or did the problem just develop? Sat for a long time? I’m not familiar with this engine, but if it’s an overhead valve. Pull the valve cover, check for obvious differences in the valve train on that cylinder vs the others. If nothing is obvious other than that exhaust rocker has more slop than the others and it has an umbrella seal on the valve stem, slide it up and spray your favorite lube, Kroil, PB blaster, ect under it. Then LIGHTLY rap on the valve stem with a brass or dead blow hammer, spraying repeatedly, using caution to not hit the spring retainer. This will usually free up a sticking valve from not running for a long time. You will notice a change in sound pitch from the valve when it frees up and starts contacting the seat.

 

[Leigh H]

Many thanks for the advice , the jeep has been sitting for about 8 months until I got the carb sorted so could possibly be a sticking valve will pop the cover off and investigate many thanks

 

[Leigh H]

I’m very new to these engines,1953 Jeep it’s had a rebuilt carb and fuel pump , started up after 6/7 months lay off , on starting engine ticking over ok , taken for a drive but after about a few minutes Sudden loss of power and very bad backfiring , stopped at the side of the road then won’t start again and had To tow it home , any ideas where to start please Many thanks