diesel will not crank

[Flamin' Fast]

i have a 1985 gmc 3/4 ton that i recently purchased. the starter that was in it would crank the engine really slow. so i found a rebuilt one some guy had, got a good deal on it and it worked great for a few hours, then i went to start my truck and it cranked over a few times then the starter started smoking and seized up. but you could still hear the solenoid click, i took it to the starter specialist close to my house (action alternators and starters) i bought a rebuilt one. installed it today and now when i turn the key nothing happens at all. the voltage doesnt drop, the solenoid doesnt click, it doesnt even try to work. what could it be?
thank you and sorry for the long post

 

[Russell]

Hey there!

Couple quick diagnostics for you here:

Check to make sure that you get battery voltage on the purple wire that runs to the starter solenoid when the key is in the crank position. If not, check to make sure that your park / neutral switch is operating correctly under the dash at the base of the steering column. If that is confirmed as working, then check your ignition switch which is found a bit further up the steering column. If it works, and there is no power being provided to the switch, then you need to be checking your fusible links at both the big positive post where the battery cable is hooked up to on the starter solenoid and up on your firewall near the brake booster.

If you have 12 volts on the purple wire when cranking, make sure that you installed the wire on the correct terminal on the starter solenoid. Putting it on the "I" post will cause the problem you are having, the purple wire needs to be on the "S" post. Of course, you need the big battery cable installed in the proper position as well.

Since everything worked prior to switching the starter out, I'd be making sure I didn't pinch any of the fusible links off the starter solenoid, and making sure that the purple wire was on the right post.

If all that checks out, then you have a bad rebuilt (which isn't that uncommon). If you have to replace it, get a starter for a 1993 GMC 1 ton 4x4 6.5L / 4l80e diesel truck. It is a gear reduction starter that is able to crank your engine faster and with less effort than the old style direct drive starters. Make sure that you purchase the correct starter brace for the new gear reduction starter (and your your regular starter if it doesn't have one!) as you can very easily bust the starter mounting tab off your block without it.

 

[Flamin' Fast]

thanks russell! you were right about the "I" terminal and "S" terminal. i had it on the wrong one. the truck starts beautifully now. just one more thing... where can i get one of those starter braces?

 

[Russell]

Sometimes starter solenoids have the S & I terminals reversed in position, which can really throw a guy for a loop if he hooks it back up exactly how he took it apart. The "I" (Ignition) terminal was used by older vehicles with points ignition systems to provide battery voltage to the coil while the engine was being cranked. Since the points use a resistive wire to drop half the voltage the battery provided to give the coil the approx 6V it needed to operate reliably, the engines would have a tough time starting when you hit the starter and dropped the battery voltage from 12 volts to 8 volts. That would mean the ignition would have gotten 4 or less volts to start the engine with, which was often not enough. The I terminal simply bypassed that resistive wire and supplied the full 8 battery volts to the coil while the starter was being turned. As you probably guessed, the "S" terminal is short for Start

As far as the starter brace goes, the best source for one is your local dealership. I understand you folks down south are able to get them for around 10 - 15 bucks plus whatever applicable taxes you may have in your state, and last time I checked GM still has both braces available for purchase, often times in stock too.

The brace bolts onto a stud that sticks out of the main body of the starter just behind the engine mount, and to a threaded hole in the engine block just above one of the freeze plugs. Just so you are aware, the hole in the block is metric thread, so you may want to purchase the bolt from GM while you are at it.