Hot start issue

[Ackattack]

I put a 4.8L into my 1990 chevy pickup. Everything seems to run fine except that it doesn't like to start when its hot.

When it's cold I turn the key and it fires right up. When hot I turn the key and it cranks for several seconds (5-7) and may or may not start. Try it again and usually it will go ahead and fire up.

Any suggestions on what to look for? I have HPTuner if there is some settings I need to tweak.

Thanks

[BR3W CITY]

Ack, there are a couple things to look at but I'd stick your head into the "After Start Enrichment" category.

When you start the motor, it acts sorta like an inverse choke, and can increase or decrease fuel separate from the regular fuel curves at start. On some modded motors, you'll SMELL them on start because the tuner scaled up the injector tables but never touched ASE, and its dumping fuel.

If your not starting well hot, take a look there first.

[aknovaman]

Verify fuel pressure and inlet air temps as well as engine coolant temps are reading correctly in both situations. Highly unlikely the ASE settings Need adjusted since it's a totally stock engine. Is it using a factory crank position sensor? Hopefully not an oreilly auto parts store one.

Post up a startup catalog in both situations too. Default hot configure should be fine.

[foamypirate]

If you have a return type fuel rail with a fuel pressure regulator on it, might want to check the FPR. My friend had a 6.0L swap with hard hot start issues, and it ended up being a slight leak in the FPR. He had fuel coming through the vacuum line. The FPR was still regulating pressure correctly, so it took him quite some time to figure it out.