Wont Crank

vertikal · June 4, 2009

does anyone know any problems w/cranking engine when warm...say shut off at store, run in and get smokes ...come back hit ignition and lights and everything come on but no start...sorta like if u were in drive w/auto transmission...then finally when get frustrated....it cranks....imagine that

Kodiak450 · June 5, 2009

does anyone know any problems w/cranking engine when warm...say shut off at store, run in and get smokes ...come back hit ignition and lights and everything come on but no start...sorta like if u were in drive w/auto transmission...then finally when get frustrated....it cranks....imagine that

Always when warm, never when cold? Battery cable tight? Maybe have your starter tested? Could be a malfunction with computer, like you described with "trying to start when in drive". Faulty starters can do strange things, like sudenly start even know starter needs to be replaced. Hopefully a pro will chime in and possibly know exactly what is happening.

Shaners · June 5, 2009

Possibly the selonoid or a bad chassis ground off the battery.

bill190 · June 5, 2009

Probably a bad starter.

Starters are electric motors with wires wound round and round inside. There can be a break in a wire...

When cold, things contract, when warm/hot, things expand...

So when cold the wires in the starter are contracted and are making electrical contact - and it starts.

But when it warms up, it expands and the wire loses electrical contact at the break, then it will not start.

I once met a guy who worked at a business which rebuilt starters. I asked him if they tested their rebuilt starters by heating them up and seeing if they still worked. He said no. I said maybe that is why I got 2 rebuilt starters in a row which would not work when hot! (I bought a new one and it worked fine for years.)

71GMC_3/4T · June 6, 2009

My 2003 died at 40K miles. Everything looked great inside (I tore it down to inspect it). I have no idea why it wouldn't start. It quit one day, then started later. Then it quit the next day and never came back. I replaced the starter.

What Bill says is right on. On some motors (and solenoids) the wires heat up and go open. Granted, that doesn't explain why mine failed cold though. What say, Bill?

bill190 · June 6, 2009

...On some motors (and solenoids) the wires heat up and go open. Granted, that doesn't explain why mine failed cold though. What say, Bill?

Right, solenoids (relays) also have coiled wires which can exhibit the same symptoms. And on some vehicles you would have a separate from the starter "starter relay". Others have this relay or solenoid built into the starter.

As to cold or hot, it is just a mechanical thing and how the wires are run inside the electrical device. And where the broken wire is. In some cases cold would make the metal contract causing a wire to move away from the other portion of the wire where the break is. In another case heat and expansion causes the wire to move away and lose contact. Maybe the wires are run up and down rather than left and right and the metal is expanding/contracting left and right.

Basically with cold/hot and metal, you get mechanical movement. Place a piece of paper between two rulers, then slide the piece of paper to the left a little to simulate heating and movement. Or slide the piece of paper to the right to simulate cooling and movement. Then imagine a broken set of wires on the left as opposed to a broken set of wires on the right. The cold separates one set of wires and makes a better connection for the other set. And the opposite with heat.

But the piece of metal or metal part (piece of paper) always moves one direction when heated and the opposite when cooled.

To make this more complex, look at an old fashioned home thermostat. It has a metal coil. This is made of two dissimilar metals bonded together. One metal expands faster than the other when heated. Below is a picture and in the bottom you can see the top of the coil. As it heats, the coil would move one direction, or as it cools, the other direction. Mechanical movement. In the picture they have mercury in the glass tube which makes electrical contact on one set of wires with left movement and another set of wires with right movement. So you get one electrical connection with cooling and another electrical connection with warming. One turns on the heating, the other the A/C (along with how you have the switch set).