Hello. I have a 1979 620 with an L20B. It hasn't been started in about five years. I have cleaned all grounds and connections. My starter has been load tested and is good. I bypassed the battery and hooked jumper cables hot side directly to starter and ground side to the block ground behind fuel pump. When cranking it acts as if it has not enough power. Cranks very slow and resricted for about half a rotation and then barely turns another half turn another have rotatation then barely turns and so on. This continues to repeat over and over. If I remove at least two spark plugs it cranks as if normal. Any ideas? Thank you. Alex

well i was gonna say that there may not be quite enough lubrication after 5 years to crank properly and possibly a little seizing... but the spark plug thing is confusing

That was my first thought too. But the oil is brand new also. The oil that came out was clean too. I think my starter is faulty even though it passed the load test.

try using a stronger battery, and if it still does it hook up some jumper cables to the battey and to another car while its running and try that out. My truck does the same thing, not enough amerage will cause that problem, it means even though the starter has been load tested the starter may need to be rebuilt due to dirty brushes within the starter.

I haven't used a bettery at all. Always jumper cables to a truck that is running. So I know it has plenty of power. I'm just going to get my starter rebuilt or get a new one and see how it goes. I also am going to take the plugs out and turn the motor by hand and see if its very restrictive. Maybe seized bearings?