Choking out. POSSIBLY

B250 LOVER

MEMBER
1987 DODGE VAN
V8
2WD
AUTOMATIC
102,000 MILES

I have a 1987 Dodge Ram Van B250 with the 318 motor. As soon as I start the van its starts puffing black smoke I rev the engine the smoking continues. This van has barely 100000 miles on it and all maitainance has been kept up VERY well. Shortly after I bought the van it wouldnt start one day and I could smell gas inside very strong, I eventually figured out that the choke was stuck. Now I am wondering if the choke could be just partially stuck closed? The MPGs are terrible also, could that be related also or is it just a super gas user? I mean I get like 8MPG. Any information that you can provide me with would be outstanding!

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

Watch the choke blade to see what happens when you start the engine cold. It should pop open about one third of the way. If it doesn't, suspect a ruptured diaphragm in the choke pull-off. You can also remove the vacuum hose from it, push the pin and linkage into the assembly, cover the vacuum port with another finger, and the pin should hold in the retracted position until you remove your finger from that port. If the pin pops right back out, the pull-off must be replaced.

There is a passage way from the right exhaust manifold, through the head, through the intake manifold, and through the left head. Check the heat riser valve in the right exhaust manifold to be sure it turns freely. When the thermostatic spring is cold, that valve closes to force all right side exhaust to go through that passage under the choke's thermostatic spring to warm it and the base of the carburetor. If that valve is rusted tight in the open position, the Chrysler dealer has a product designed specifically for that called "Mopar Rust Penetrant". It works WAY better than WD-40.

After three minutes the choke should be wide open. If it is not, suspect that passage under the spring is plugged with carbon. That used to be a real common problem before we had cleaner fuels. In addition, there is an electric heater built into the choke spring and a thermal switch mounted near it. Measure the voltage on that heater to see if it's working. You can also tell by leaving the ignition switch in the "run" position without starting the engine. If the heater is working the choke blade will start opening on its own after three minutes.