I have a 1985 B150 van with a 3.7L (slant six) with 58000 original miles. During the summer it would run for 20 minutes and then die as if it was running out of gas or the choke was screwed up. It would start again but run for less time each time. I replaced many parts and did all kinds of tests, vacuum, fuel pressure, spark. Replaced the egr valve, fuel pump, electronic spark computer, fuel filters. Then a friend mentioned blocking off the third hose from the fuel filter to the tank, thinking that it would get more fuel that way and it worked, the problem went away.
Now that it is winter though, it is taking at least forty pumps of the gas to start it and then there is a huge plume of smoke, white, and very gas smelling fumes and I have to rev it several times to clear it out. Once it hits fast idle and the whole rest of the day it runs fine. Every start the rest of the day no matter how long it starts right up no problem and runs great. The next moring the same thing happens, no start without pumping the hell out of it and then the fumes again.
Any ideas?

Thank you,

Tom

 

Have you check to see if the choke is closing on the first start of the day? Sounds like the choke is staying open.

 

Look down inside the carb and move the throttle to see if the accelerator pump is squirting gas.

 

The choke was staying open but if I pumped the pedal it would close to within a 3/32". I adjusted the joke to close as far as it could and now it starts within a couple pumps and about 4 cranks of the engine but it does not go to high idle for about 4 minutes. I have to rev it to keep it going and when left alone it puffs and puffs for about 4 minutes and then it seams to clear out and the fast idle kicks in and runs great for the rest of the day. The low idle at first and the fumes and exhaust are very annoying.