I'm trouble shooting my SBC starter. I did a check of my electrical and here's what I get. - I have power going striaght from the battery to the big terminal in the middle. Checked with a meter and I have 12.x volts going to it. - When I turn the key to the ON position I have power going to the R terminal with the same 12.x volts. - When I turn the key to the START position... I get about 2.3 volts to the S terminal. IS THIS NORMAL? Shouldn't I be seeing 12 volts there too?
12 volts is a requirement for the starter to spin on the "S" post.The main post must also be energised with the battery cables 12 volts. Oldmics
What trouble are you having? If you short the batt terminal to the "S" terminal does it engauge and spin over. if so you might have a problem with your switch or wiring to the starter.
well it all started with what I believed to be a dead starter... then it evolved to a SBC shimming a stuck starter... but now I'm back to reviewing the electrical input to the starter. Here's another thread I was working on http://www.jalopyjournal.com/forum/showthread.php?t=373885 Here's my theory.... my starter WAS working and then all of a sudden it started getting stuck in the flexplate... I believe that maybe the bendix is getting stuck becuase the flexplate is NOT being moved and thus not helping to throw it out. (??)
Start by removing all wires. Batt cable should be 12v. Check. Turn on key to start position find the wire that has 12v. This wire goes to S terninal. If there is no 12v wire in the start position, you will have to determine which wire is the harness power feed(usually the one with the 3/8" ring terminal on it ) and secure to the Batt positive. Alla same, find the one that has continuity to the Battery + cable with the key in run position. Now recheck for the 12v hot wire for S terminal. Now you should have one wire left. This goes to the R terminal. Non left, keep reading. Batt terminal is 12v at all times, even key off unless equipped with an intermediate solenoid. Not common on Gm products. Usually consumer added if present. 0v key off, 12v key on if present. R terminal is 12v out from solenoid when starter is engaged. 0v when key is in run position. 0v if solenoid cannot pull in bendix. This terminal not used if HEI or electronic. Use an ohmeter probe from Batt term (3/8"stud) to R terminal. Manually pull in bendix with a bar between starter frame and bendix gear. Should have continuity at full extension but at no other time. Be sure all cables and wires are removed from solenoid before manually engaging. manually engaging bendix also makes the electrical contact in the solenoid and it will run if connected therby throwing the bar into your just buffed 10,000 dollar paint job. S terminal is 12v in from wire when key is in start position only. 0v at any other time. This is the terminal that engages the solenoid. Starter can be tested for motoring by putting ground to the bushing stud on end of starter and positive power to the stud that is directly below the batt terminal and between the R and S terminals. Solenoid operation can be checked by using the same ground connection and touching the positive lead to both the Batt and S terminals at the same time. Note that there is a lot of rotational force when the starter starts to turn so be sure it is securely tied down.
Right, I forgot this is the traditional forum. So, Traditionally, you might want to make sure it is in gear with the switch on and power connected to the starter so when something accidently gets shorted at the wrong time it can run over you or fall off the hoist. 440, If four wires kick your ass what are you going to when it gets serious? Safety police says disconnect all wires.
Well after a day under a car in the hot sun... here's the update as of tonight. Disconnected all the wires and started back with basic wiring just to get the thing to crank. 1. I connected the main battery (+) cable directly to the large terminal on the large starter terminal 2. Connected a test wire to the S terminal so that I could manually touch the other end to the battery to get it to kick over. Touched the wire and got the same results. I decded it had to be the starter. Maybe I bought a bad starter at NAPA? Went down to PepBoys to have it checked (NAPA doesn't check them)... and what do you know. It spun right up and tested GOOD. DING DING DING.... It's the battery. I had just bought a new DieHard last Saturday so I never suspected the battery. That and the battery was showing 12+ volts. Cranking AMPS???? Swamped a batery from my other car and sure as shit the thing cranked over strong. BUT WAIT THERE'S MORE..... Thinking I had finally licked the problem I decided to reconnect the wiring as it was ..AND NOTHING! ARGHHHHHHH.
Did you figure out the problem? I have been going through the same problem on and off for over a year.
By reading your last update, it sounds as if the jumper wire to S terminal works when the new battery was installed. If so, then does not work with the normal S wire connected, I would check the following: Neutral safety switch, bypass the switch and try. If it cranks it's the neutral safety switch. If still no cranky, then ignition switch is possibly bad in the START position. To check jumper B terminal and S terminal on the ignition switch and see if it cranks. If so then ignition switch is bad. If not then wiring is bad, probably between neutral safety and solenoid. To check, simply put a voltmeter on each side of the neutral safety and check for 12V (while cranking). If both sides are less than 12V then wire is bad from ignition switch to neutral safety switch. If only one side is less than 12V then wire from neutral safety to solenoid is bad. Good luck
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