Does Not Like to Start When the Engine is Warm

[DGrant09]

We have a 390, fresh rebuild and new battery that is hard to start when it warms up. It will act like the battery is weak, but it is new and once the engine cools it will start fine. Once this week I jump started it when this was occurring. I have not seen any indications of a weak battery or a slow alternator (dimming lights etc..). Should I be looking at the start system or charging system. These are the only two items we have not replaced recently!
Thanks
Dan

[michael69]

Sounds like you may have a starter problem. When starters start going bad they will drag and act like battery is weak when they get hot.

[19674x4]

sounds like a bad starter to me. check all connections as well

[Joshpow]

Possible timing issue. If the timing is extremely out of whack, it may still run ok and start fine cold. After the engine gets warm it will sound like the starter is not powerful enough to spin the engine. My 72 had the same problem, and a re check on timing showed it was off. I reset the timing down to factory specs and the problem went away. Don't know if this is your problem, but it may be worth a try.

[DGrant09]

Thanks for the ideas! Looking at the starter and what was mentioned above I picked up a new starter and ran the truck to the shop. We looked at the amp draw to the starter when it was acting up and sure enough it was excessive. Now we have a new starter!! All I have left is the alternator and the engine will be new! Ouch!! It is running nicer -
Thanks for your help!!
Dan

[BiggDogg]

I've been having the same problem but haven't had a chance to investigate it yet. Pretty sure its the starter though cuz its pretty old. Any starter brand recommendations before I go shopping?

[willowbilly3]

After you attempt to start it, go feel of all the battery cable connections. If any are hot you have a bad connection. I agree it is probably a tired starter. I would go have a system test done by a shop with a Snap-on AVR, Vat-40 or similiar test equipment. They can test the whole sysrtem in about 5 minutes.

[DGrant09]

Well, as for the connections and wires. The only wire that is old runs from the start relay to the starter. I've had wires look ok but were corroded inside the insulation to the point they no longer worked. As for the wire temp - Yep they get ^&@# hot when it is acting up!
We'll see today how the truck does with the new starter. I have to run up to Fairbanks and back.

[DGrant09]

Quick update.. The truck has done great with over 700 miles since the new starter went in on Saturday!!
Thanks again,
Dan