I have a 1991 D150 318 swapped into a 1956 Dodge Regent. The engine ran about a year ago, but now it only misfires and won't stay running. Any ideas?

 

is it carburated or fuel injected?

 

Fuel injected

 

Check the cap,rotor plugs and wires. Will it stay running if you keep your foot on the gas?

 

Cap and rotor good? Plenty of fuel? Good fuel? How many miles on the engine? When you dropped it into the car, did you check the timing chain beforehand? How is the fuel pressure? I assume you put FRESH fuel into it.

The simplest and easiest thing to check is the cap and rotors to make sure they are good and a plug wire isn't gnawed or shorted out on a manifold.

 

I've already cleaned the distributor, changed the plugs, and checked the wires. If I put it to full throttle it tries to run on a few cylinders, but misfires and dies after a few seconds.

 

All of the basic stuff like good fuel and fuel pressure is all good. I think it's something electronic related as it only happened after it sat for a while.

 

Fuel related is the easiest and cheapest to look at so let's do that first. Your engine has a TBI setup. How are you supplying fuel? In tank pump or an electric pump near the tank? If you have an electric pump near the engine, move it closer to the tank. As close as possible as electric pumps are great at pushing, really bad at pulling. How did you plumb the fuel lines? Steel lines with rubber connectors or just rubber hose all the way? Check the pine between the tank and the pump. If there are ANY cracks, or a rodent gnawed part way through the hose, you're sucking air. You aren't getting enough pressure as the fuel is mixed with air. This makes it too lean and is a fire hazard. You have oxidizer (air) mixed with the fuel and it can burn INSIDE the line. Fuel starvation can cause misfiring pretty bad. You can also break out the Mark I nose and see if you smell any fuel.

The key here is it sat. Rodents do a LOT of damage to equipment that just sits. Sakes, you might have a blocked exhaust. That can cause misfiring but not often. A vacuum gauge will tell the tale there.

 

There have been no rodents living in the car, and the fuel line is Intact. I don't have any problems with fuel pressure at the engine. I'm still using the factory fuel pump. A few of the cylinders try to fire consistenly, the others just misfire.

 

Did you check the wires are going to the correct cylinders? Put a timing light on the coil wire and see if you have constant spark. If so then check the cylinder wires.