possible fueling issues
 

Ok guys i posted on here awhile back thinking i had gelled fuel well i changed my fuel filter put some antigel and conditioner in the filter and topped it off with fuel b4 putting it on got her running but im still having the same problems....it chugs at idle almost like it has a really lopey cam....wop wop wop....and it bogs when im driving sometimes causing it to stall my buddy thinks im getting air in my fuel somewhere...im gunna try the clear fuel line trick this weekend but any ideas what 2 check things to look for it doesnt chug and bog all the time just sometimes so im a bit confused as to what the issue is please help any help is good help thanks

year of engine?

82 mechanical 6.2

Plugged filler cap vent?
Restriction in the fuel return line?
Plugged screens @ IP inlet?
Dying lift pump?

Sucking air is a real possibility?

Is the lift pump clicking? Down on the frame. Its an electric pulse pump. I have an 84. It also has a mechanical lift pump on the engine like a gasser. Check the fuel lines good. I had some rotted lines that were leaking when I got it and put it back in service.

??? I'm absolutely not an expert but AFAIK the mechanical 6.2 has no other lift pump except the mechanical pump on the passenger side, towards the front of the engine.

At least my '85 never had one to my knowledge. Also my service manual makes no mention of it either.

To the OP, racer55 pretty much has the suggestions covered.

I would also add the pick up screen in the fuel tank itself.

I had an Olds diesel that was acting like what you are describing. Changed the fuel filter, ran new line all the way, clear line to check for air, etc.

Finally dropped the fuel tank and removed the sender/pick up assembly.

The sock looked like I had a science experiment growing on it. I removed the sock from the end of the pick up tube and cleaned the inside of the tank.

Installed the sender WITHOUT the sock and bought a cheap inline clear plastic fuel filter from my local auto parts store.

I then installed that under the hood pre normal filter so I could monitor if any sludge, dirt, etc. was being sucked up from the tank. Worked like a charm.

I have done the same to my '85 GMC with the exception of installing a low pressure electric fuel pump close to the tank and bypassing the mechanical lift pump.

Also works well and is easy to change if it gets plugged.

Sorry for the long post and I hope you discover what the problem is.