I just bought this '98 Dodge Dakota Sport manual transmission. I was told that at times the truck won't start but once you tap this device with a screw driver it starts right up.
What is this part?

 

Welcome to the forum..the part is your Powertrain Control Module (PCM). It is the computer that controls and monitors your engine and fuel management. Sounds like yours has an internal problem. They can be replaced. Look online for rebuilders and you can also search topics here from others who have had theirs rebuilt or replaced.

Jimmy

 

It may easily be bad - you're describing the effect of a bad connection.

HOWEVER.

Before I replaced it, I'd:

a) Disconnect the negative battery cable from the battery.

b) Then, remove and replace each of the three connectors at least five times.

c) Reconnect the negative battery cable and see if the problem appears to be fixed over at least a dozen starts.

If it does, then it's just oxidation or fretting at the connectors. Disconnecting/reconnecting will polish the connectors by the rubbing friction; and can make the bad connection be not so bad. (I firmly believe over 50% of the "bad ECU" posts are actually just bad connectors, and the removal/installation did the cure, not the swap itself. But that's a WAG, no basis in evidence, just a gut feel from decades with electronics.)

If that does appear to fix it, grab a tube of dielectric grease (or "bulb grease" as it's also known) and do the a) again, then clean the cavities out with cleaner (such as CRC's Electronic Component Cleaner, available at most auto parts stores - or another brand of the same thing!), put some dielectric grease in the cavity, and then repeat c).

That will help to seal it against oxygen to keep it working well as long as possible.

RwP

 

RalphP I agree 100% especially in the rust belt states bad connections are very common problems. Out West thats not common at all but can still happen. Start with the simplest solution first