My truck will start just fine when its cold..but if I drive it about 30 miles, it won't start again, until it cools down(15 minutes or so).
It gives me the slow turnover sound, like a low battery.
jumping doesn't help, it just has to sit 15 minutes to restart.
would you think that maybe the bushings in the starter are heating up?

 

Starter could be getting weak. A hot motor is harder to start that a cool motor. I had a similar problem but it was my battery. You could jump it and it would work fine.

 

You're ignition timing may be out of sequence. Did you replace your timing gear and chain recently? If you have alot of miles I would consider replacing both. Then adjust your timing to spec. If the timing is off with a hot engine, this can affect starting, also.
Heat also can affect the IM (ignition module), on the distributor, once the engine is warm. The engine will start hard and seem like it's misfiring or cutting out as you're driving. My '87 f150 w 170k had this problem. Since I replaced both, the chain, gears and the IM, it runs great HOT OR COLD.

 

He does not have a starting prob. He has a cranking prob unless there is something he did not mention on here.

 

yes, a cranking problem.
I can go out in the morning, and the truck will crank right over.
The truck will run perfect.
Lets say I drive about 30 miles.
If I then shut the truck off...it will not crank over again, it gives me the (slow weak battery sound)
If I let it for about 15 minutes and the truck cools down.
It will then crank right over and run perfectly.
I have tried jumping it, to no help...I have even replaced the battery.
the truck just has to sit to start

 

Sounds like the starter is getting too hot while the engine is running. Heat increases electrical resistance, and that reduces current flow. Less current equals less magnetism, and therefore, less torque. If the starter is old and worn, then there might be too much resistance to overcome on a warm starter, but when it's cold it is low enough that it can get enough current flow. I'd do a few voltage drops on the system to be sure, but the starter is propably bad. By the way, to do the voltage drops:

Main Power: Use your multimeter to test for voltage drop between the positive battery terminal (red meter lead) and the "B" terminal on the solenoid (black meter lead). Should be no more than 0.2 Volts when cranking. Otherwise, there is excessive resistance in the cable.

Starter Solenoid: Hook your meter Red lead to the "B" terminal and the black lead to the "M" terminal and crank. Voltage drop should not exceed 0.1V.

Motor Cable: Hook up the red meter lead to the "M" terminal on the solenoid and the black lead to the Positive Pole on the Starter (where the cable bolts to the starter) and crank. Voltage drop should not exceed 0.2V.

Ground: Hook your meter red lead to a secure and clean spot on the engine (accessory brackets, block, head, intake, etc) and the black lead to the negative battery terminal and crank. Voltage drop should not exceed 0.2V.

If these all check out, then it is almost certain your starter is the culprit.

Note that none of these tests require breaking connections. These tests are for testing actual functioning circuits while remaining undisturbed.

 

I would replace the starter. My '92 was making an odd noise at start up for about a year. The starter finally went totally dead about 3 weeks ago. I could not figure out what was causing the noise. When the starter was replaced the noise went away. My point is the starter can go bad gradually. If your starter is original you have gotten some good service out of it.

 

I have a similar problem, replaced battery and starter, it turns over enough to start when hot, but just barely. I'll check the timing next,it may be out a little, like Jim says.

I had a Taurus that did this, it was the battery, and a Zephyr (remember them??) when the timing was out of whack.

 

What I failed to mention is that when the engine is hot, and the timing is off, the engine will crank over hard and slow...like it's working against itself, similiar to a bad battery or a bad starter. If you let it cool a little while, it will crank over normally and start.

 

I have an 87 f150, and it used to do the same thing, it is called starter drag, just replae teh starter and it should work fine. It worked for me.