1989 Dakota, 3.9, 5 speed. The fuel pump went bad on it a month or 2 ago. We replaced that and the gas gauge doesn't work now. But maybe a week after replacing the pump, the truck falls on its face at 3000 rpm. It felt like it was hitting the rev limiter. So I replaced the coil. Still didn't help. I am wondering if the sending unit fell over in the tank when re-installing it, and its sucking air. But on a full tank of gas you think it wouldn't do this. I don't know where to go from here.

 

check your exhaust, make sure it's not restricted. The best way to check for a restriction in your exhaust is connect a vacuum gauge to an available port on your intake manifold. It should read around 15 inHg at idle and steadily start dropping as you crack open the throttle.

 

if you snap it open it should drop instantly to 0 and then come right back.

 

9652dakota, thanks I got my readings turned around. Yes it should drop to 0 and come back to 15 inHg and drop steadily if it's restricted.

 

I'll try that tomorrow. Thanks.