One thing to remember though, these things are not real good on mileage anyway, turning up the pump will give it a nice power increase but make real bad mileage.

 

I owned three of these diesels and all of them got over 15mpg city and near 20 hwy turboed and the pump turned way up. I really dought that the tach sensor had anything to do with the miss beings that is an all mechanical pump and is not even connected to the tach. I will bet you are slow in time or have pump problems. Best thing to do with the glow plugs is pull all the plugs install autolite 1106 plugs put a switch on the relay so you can turn them on manually and you will never need another glow plug and the never swell these are a 12 volt plug instead of the original 6 volt it takes about 30 seconds in the winter to heat them up to be able to start but you will never have to replace another.