74M35A2
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Starters and their solenoids are relatively simple. Here is the math on them, specifically the solenoid:
The starter solenoid does 2 things:
1. It throws the pinion out to engage the flywheel. This action is a strong spring return.
2. It has a copper bus bar inside the rear cap that makes the connection between the two large B+ posts, sending high current to the starter motor.
The solenoid has 2 separate coils of wire within it. The first is a higher powered "P" coil (pull coil), which throws the pinion out with enough force to work in dirt, moisture, and down to -40 temps. The second coil within the solenoid is the lower powered "H" coil (hold coil), which holds the pinion out, and the copper bus bar connected across the two large B+ solenoid terminals. You can ohm check the resistance of each coil, the values should be able to be found on the net. When you are testing, it sounds as if you are only applying power to the "H" (hold coil), since you need to engage the solenoid by hand first. Or, the "P" coil is shot and not working. The P coil will have a lower resistance (more power) ohm reading than the H coil. You can also measure the resistance across the two large solenoid terminals when the solenoid is fully engaged, it should be near 0 ohms.
The starter is often to blame, when in many cases, other issues cause problems. These include a locked engine/trans, improper battery voltage at the starter, loose/corroded connections, weak grounds, starter control box (not sure if your vehicle has this), etc....
You can test the majority of this with the starter and solenoid on the truck. For example, apply 24V via jumper cables to the short large solenoid lead which goes into the motor case to see if the starter motor will spin.
Get an internet diagram and test measurement values for the solenoid of your starter off the net and go from there. Problem may be truck side if the starter tests OK once you know which connections do what.
The starter solenoid does 2 things:
1. It throws the pinion out to engage the flywheel. This action is a strong spring return.
2. It has a copper bus bar inside the rear cap that makes the connection between the two large B+ posts, sending high current to the starter motor.
The solenoid has 2 separate coils of wire within it. The first is a higher powered "P" coil (pull coil), which throws the pinion out with enough force to work in dirt, moisture, and down to -40 temps. The second coil within the solenoid is the lower powered "H" coil (hold coil), which holds the pinion out, and the copper bus bar connected across the two large B+ solenoid terminals. You can ohm check the resistance of each coil, the values should be able to be found on the net. When you are testing, it sounds as if you are only applying power to the "H" (hold coil), since you need to engage the solenoid by hand first. Or, the "P" coil is shot and not working. The P coil will have a lower resistance (more power) ohm reading than the H coil. You can also measure the resistance across the two large solenoid terminals when the solenoid is fully engaged, it should be near 0 ohms.
The starter is often to blame, when in many cases, other issues cause problems. These include a locked engine/trans, improper battery voltage at the starter, loose/corroded connections, weak grounds, starter control box (not sure if your vehicle has this), etc....
You can test the majority of this with the starter and solenoid on the truck. For example, apply 24V via jumper cables to the short large solenoid lead which goes into the motor case to see if the starter motor will spin.
Get an internet diagram and test measurement values for the solenoid of your starter off the net and go from there. Problem may be truck side if the starter tests OK once you know which connections do what.
