Why am i having trouble starting when warm?

[Phx Mike]

Originally Posted by Midcont

The car has a small block 351w-427R.
It starts up immediately when cold. When warm, sometimes two or three attempts with a couple of seconds of cranking, unless I catch it just right with a few pumps on the gas pedal and just enough pressure on it while I start.
A new fuel pump was installed at the beginning of summer. I don't really remember having this issue before it. The mechanic says its due to the high levels of ethanol in the fuel. It took all summer, but I last week put in 5 gallons of 104 octane and filled the rest with 94 octane to see if this rectified the issue. It didn't.
I've also read it could be the starter not working well when warm.
Any thoughts or suggestions?

Every older carbureted car I have ever owned exhibited this behavior to some extent including my current Cobra. My rule of thumb has always been - when cold (and I mean like first start of the day or after sitting for several hours) use one good pump and then crank with the throttle 1/4 to 1/2 open. When warm, don't touch the throttle just turn the key. Some cars like just a LITTLE throttle on a warm start but not much and if you pump it warm you will almost always flood it and it will take a bit of cranking to get the extra fuel out (and a nice black cloud when it finally fires). My old 390 Galaxie was like this, my small block Camaro, my F-150 with the 351W...all of them.

If the starter is cranking quick when warm it's not your starter.

[Gaz64]

By all of the replies so far, your starter sounds fine.

What carburetor have you got?

Photos would be good.

[xb-60]

Originally Posted by Phx Mike

....When warm, don't touch the throttle just turn the key....

I agree with Mike. If the engine is hot, don't touch the gas pedal at all (initially). Wait until you hear the engine just start to catch on a couple of cylinders and then add just a touch of pedal.

Cheers,
Glen

[AC Ventura]

It seems clear you need to try the spacer idea, as its simple and clearly other guys say it works.. However, if that doesn't solve it, then it means your near static fuel is most likely boiling in the line to the carb, once the engine is shut down. When it boils, AKA Vapour Lock, it creates an air pocket that can in effect, stop fuel getting to the carb.
One way to overcome, is to set your bonnet open slightly and alter your radiator fan, so it stays on longer after shutdown. Renault did this with the little 5 Turbo and it cured the hot start issues, which originated from a sometimes red hot turbocharger.
However, the bulletproof method is to have a return line back to the tank from the carb, with an in line regulator. This way cool fuel from tank is constantly circulating at idle and can't boil.
As with all fuel line fittings, monitor tightness regularly as failure of these is what causes engine fires. Metal air filter elements are better too.