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-   -   Bench testing a GM starter (http://www.hotrodders.com/forum/bench-testing-gm-starter-65272.html)

schnitz 07-05-2005 03:33 PM

Bench testing a GM starter
 
Here's a good question for those electrical gods on this board... If you have a fully charged battery (12.76 volts), a questionable GM starter, a set of jumper cables, and a remote starter, can you tell if the starter is bad? I only ask because I'm trying to get my plowtruck to start, and it makes no effort to turn over. I tried the afformentioned action, jumped the solenoid, and the starters (4)would engage like a good one will. However, when I install it, none of the 4 that I tested would do anything but kick the gear out to the flywheel (using the remote starter--without it, nothing happens at all). Won't spin the engine over for anything. I can grab the bottom crank pulley and spin it over by hand, so it's not locked up. The headlights, also, will not dim when the key is turned, if that helps. I'm stumped here, and just need a nudge in the right direction.


Thanks in advance, Chet

poncho62 07-05-2005 04:33 PM

1st....The snow is gone, Schnitzy.....................

Are you using the same solenoid on all the starters...may be your problem.

If it won't do anything when turning the key. you probably are not getting power to the ignition terminal of the solenoid.

Try putting to the bottom terminal of the starter, under the big one that you bolt the cable to. It should spin but not engage. Sounds like the solenoid to me.

1982 SS 07-05-2005 04:38 PM

I'm assuming you are using a Ford type Solenoid. Make sure you have the power wire to the large lug on top and jumpered to the small lug to engage the starter and the kickout mechanism.

schnitz 07-05-2005 05:18 PM

Poncho, have you looked at my plow truck... :rolleyes: LOL!

No, I'm using the solenoids that are on each starter. If I take a multimeter and measure voltage to the hot (big terminal), I should have right close to the 12.75 volts, right? I don't believe that it would have to run through the plow solenoid in order to run the truck.

1982, it's got the regular GM solenoid on the starter, and then the plow solenoid mounted to the very rusted out inner fender. The cables are all in need of being new, but the truck started before, so I'm stumped as to why it won't start now. It's not like the truck even jiggled over a pothole, it never left my driveway.

Thanks, Chet.

poncho62 07-05-2005 05:55 PM

Sounds to me like the power isn't getting to the solenoid.

On the bench, connect your battery to the big terminal and a good ground.

Take a screwdriver and short straight down from the big terminal to the other big terminal just below it. The starter should spin but not engage. Short from the big terminal to the small terminal (closest to engine) and it should spin and engage. If it does all this, you have a wiring problem.

schnitz 07-05-2005 06:13 PM

Quote:

Originally Posted by poncho62
If it does all this, you have a wiring problem.


Dratt!! Just about the time I was getting brave with electrical work.... Zap! it bites me in the multimeter.

I'll get it yet. It can't be THAT hard to figure out.

Thanks again, Chet.

NDNslicks4me 07-06-2005 10:46 AM

Is the battery grounded to the block? and the block to the chassis?

docvette 07-06-2005 09:21 PM

Starter
 
Doc here, :pimp:

Assuming you still have the starter OUT of the car and on the bench...

Place the starter TIGHTLY IN THE BENCH VISE...(They can throw a wallop when they spin up! :pain: :nono: :pain: )

Remove the solenoid..two mount screws and the bolt on the main starter winding screw.

Ground the vice<----READ with a jumper cable, CAREFULLY touch the positive cable to the main winding copper stub coming out of the starter body..The motor should spin up Real fast.........not first slowly and then build speed..(If that happens , rebuild or replace the starter) If it spins right up it's just fine.

http://i4.photobucket.com/albums/y14...terRebuild.jpg

Next REMOVE the starter from the vise, and replace it with the solenoid..CAREFULLY hook up your positive jumper cable to the TOP main bolt..Then jumper a smaller wire to the "S" terminal ...

Get your Volt ohm meter, and measure the voltage at the bottom main bolt It should be 12 volts, and go away when you remove the "S" jumper..If not, the solenoid is bad...Replace the solenoid.

If both work well, reattach them and test the whole starter in the vise, If it works fine in the vise, you have a vehicle wiring problem...If it fails in the vise after reattaching the solenoid, the copper stub going into the starter has probably melted the solder under heat and is intermittent on just how much torque is put on the bolt...repair or replace the starter motor.

Doc :pimp:

schnitz 07-08-2005 03:21 PM

Dang Doc! That is impressive. I'll be testing all 7 starters I have this weekend using that method. Thanks.

In a while, Chet.

docvette 07-08-2005 05:09 PM

Starters
 
Doc here, :pimp:

Let us know how it turns out...(The Butler did it...lol... :D )

Doc :pimp:

schnitz 07-14-2005 02:32 PM

Two starters (and the solenoids) test good. Another 2 starters are borderline (just don't spin right up as quick as I think they should--BTW Doc, a starter is a bit torquey if it's not clamped into the vise good and tight LOL!) and have bad solonoids, and three others are absolute junk (one of which isn't even a Chevy starter :rolleyes: ). I'm leaning now towards re-wiring the dang thing to get it to run...

Thanks guys, Chet.


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