Purple Starter Wire Blues

[AcampoDave]

I've been helping a friend diagnose a starter solenoid problem. It just barely clicks unless I jump it from the large battery cable post to the"S" post of the solenoid. The S post is still using the tiny factory purple wire from the ignition switch down to the nuetral safety switch, out the firewall bulkhead and down to the starter. The truck is converted to an automatic transmission and although the purple wire seems intact at all locations, it just doesn't seem to be delivering the power needed to kick the solenoid. The test light reveals that it functions properly and the light is bright when not connected to the starter, but illuminates more dimly when connected. I can hear a very faint click and the wire gets warm and these symptoms repeated themselves with a different solenoid. The starter works fine when I jump the posts and also when I test it with jumper cables on the floor. Is it possible that the factory purple wire just isn't heavy enough to handle the job of firing the automatic style starter. Also, a direct shot from the battery to the firewall side of the bulkhead will only kick the starter part of the time. Any thoughts?

[franken]

The size of the wire isn't the issue, its bad grounds, or resistance in the long path from the battery to the solenoid. Most will say use an additional solenoid, but to my mind adding another part to a problem that isn't understood is not making things better.

Think about the electrical path to run the solenoid from the low current side of the battery all the way to the solenoid. Disconnect and clean all those things. Now do the same for the ground side.

Get a voltmeter or DVM. Measure the voltage at the solenoid S-terminal to ground with the key in the start position. Use a few different spots as ground. 12.6V is the ideal, but 12.? is ok. You may need to make a cliplead ~6-8' long with alligator clips on each end so you can see the meter from inside the vehicle. This should just be part of the troubleshooting arsenal.

The solenoid circuit isn't getting the current it needs so it isn't working right...

[franken]

For a slow crank issue, look at the big ground location (battery to block is best, never battery to frame) and condition of both large cables/connections/connectors.

[AcampoDave]

Franken, thanks for your help. I checked everything you said and it all checked out to be good. The real problem was that I had been swapping solenoids without realizing that some have different plunger diameters than others. In my haste to get things done, I had placed a large bore solinoid on a starter with a smaller plunger causing it to bind sporadically in the bore. This was causing my off and on again malfunction. I never knew that all Chevy solenoids were not created equal, but the shorter lengths of the various ones I had on hand should have been a clue. It took a while to figure it out, but I learned something new anyhow.

[Rich 5150 69]

Dave I`ve had the same issue for years, I`ve ruled it down to to much resistance in the bulkhead plug when the under hood temps rise, when my truck was running during very hot days and I shut it down I knew it would not even begin to start, then I found out by unplugging the bulkhead and plugging it back in it would fire right off, been thru all the grounds and added new with 00 welding cable, engine to frame, frame to cab, cab back to engine...battery to engine,

[63burban]

Solenoid is shot

[stsalvage]

what is it with people and no pics.Trust me we are all 5-12 year old boys girls are way better at under standing things.

Looks like you guys caught me with my pants down I do not have pics of my 1965 chevy truck engine build.It was with all the wire harness with the HEI to the starter .Looks like i will have to get on the ball and take pics on where the wires go and what wires not to use on a 1964--66 factory re pop M&H new harness.So i'm like you guys not on the ball with pics.But if you need any pics on Auto steering column for power glide pics alt pics water out let pics.Plug wire throw the motor mounts using the 1973 corvette wires for the HEI system I have it and pics Even have pics for the 1972 booster bracket and power steering bracks where and what to have.Ya i do that much more on all 12 trucks i owned

[AcampoDave]

http://rmcavoy.freeshell.org/starters.html this is good