Really Bad Gas Mileage???

sorry guys its been pretty cold out here lately so i havent really had a chance to look at it yet...dam calgary winters

but atleast now when i do go to look at it i will have an idea of where to start.

like i said before i was pretty dam happy with 425km / tank....but now only getting 270km / tanks something must be wrong

thanks again..

the first thing I would check is the O2 censor if you have one

would a fuel pump cause such a problem?

cause after i re-did my head gasket like ig ot 20 miles less on a tank which i was like hell with it it aint that bad, but when i replaced the fuel pump all of a sudden i got 50+ miles on a 1/4 tank

i have changed the o2 sensor like a year ago....and it didnt really seem to change the problems i have been having....

how would i go about checking to ensure that the new o2 sensor is doing what it is supposed to??

hook up a volt meter to it, it'll give you a reading betwen 0 and 1. should be around .5-.6

whats a volt......just kidding

but should the engine be cold or warm when i do the test .... or does it not matter?

It matters.
If you have a one-wire sensor, most B2200 carbureted (non-heated) you have to wait a long while close to operating temp.

On heated sensors (3-wire) don't have to wait too long until you can get an output reading.

well its a 1 wire o2 sensor and when i measure the output it seems to be a steady 0.45volts

is that within an acceptable range?

thats pretty good, little on the lean side

is that at idle?

rev the motor at various rpms and see what you get. also if you can possibly hook up a volt meter to the O2 sensor while you are driving and check that way, you'd get what the truck is running at (rich or lean) at your crusing speed

and if you still haven't checked, as russ said, check your vacuum advance line. have you checked timing? check timing and see if it is advancing as you rev the motor

well there is definatley no vacuum coming out of the line that goes to the distributor...i attached a picture and the line highlighted in red ....when i take that off it doesnt change the way it runs and there is no suction .....so i guess i will have to look for a vacuum leak.....althought i did just quiclkly run a torch around the carb to see if i found a spot where it changed and i didnt find anything but i will keep looking