Just had engine rebuilt with new starter and fuel pump. Starts and runs great, but a couple times while on the road I've stopped for a few minutes break, and when I try to start the car it acts like the battery is almost dead (engine turns very slowly or solenoid clicks). Then sometimes after a break the car starts up just fine. The alternator has some age on it and the alternator gauge stays right in the middle - not showing any charge or discharge. I have a new alternator that I'll put on today. Any ideas why the engine is sometimes turning over slowly after getting hot?

 

check your timing it maybe advanced a bit too much

 

If it is turning over slowly there are a number of problems it could be. If the solenoid clicks it sounds like your battery is not charged which probably means that your alternator needs changed so i would check that first or put a volt meter on it. Also Older mustangs and almost any cars if you leave them at idle they tend to get hot and when you shut it off and then try to start it again it will not turn over or turn very slow but i would try the alternator.

 

i'd say as well try retarding ignition by a couple of degrees to see if it improves

 

Also,,, check your battery cables closely, the ends on the new (made in China) parts store cables are not so great, plus when poor terminations are added to poor quality copper, plus cables that are more insulation than cable, hot start issues can become common. (especially with a new "tight" engine)

I ended up with a spool of super quality cable so I make just about all of my battery cables from scratch now.

 

Lots of good advice so far..If the engine cranks over great when its cold but not when hot you may have a starter going bad if all of the cables and connections are good..Are you running headers?..Sometimes the heat off of them can play havoc with your starter..If the solonoid is clicking that is usually a sign that it is not getting enough current from the battery..Either the battery voltage is low or its just not getting there because of cable/connection problems..

 

This is great information. I have had the same problem with my 1964 1/2. Both battery and alternator are new, as is the solenoid. When I'd get the "kill" problem, it sounded like the solenoid was trying to grind itself apart. After sitting (sometimes as much as a day), it would come back to life.

How do you deal with the heat issue from the headers?

 

Gosh mustangs all have this problem or what!? My car also does not start well after being driven and sitting for a few minutes. With mine, the engine seems to turn over fine, but it takes awhile to finally start. I am assuming it is vapor lock, because I have one of those timing guns that allows you to set the timing on the gun itself then use the cars timing pointer (or w/e it's called) to get it right. How can I eliminate this PITA?

 

A PLASTIC carb spacer may help with this hot start issue, often the fuel will boil out of the float bowls, leaving some of the less volatile fuel residue in the bowl, The fuel pump will have to pump the bowl full again and then the engine still has to deal with the "bad gas" till it makes it's way through the engine, partially fouling plugs along the way.

This is especially an issue when the manifold heat riser is intact, and/or when using an ALUMINUM bodied carburetor. I usually block the crossover passage or use a manifold that has no provisions for a heat riser, AND use a spacer when there is room.