Hot start problems

[kytoploader]

My car starts great when cold. However, about 80% of the time when hot I have to crank it quite a bit before it starts. When it finally starts it sounds like it is flooded. Any ideas?

I currently have a Saleen supercharger, Brenspeed tune with GT500 fuel pumps. It has new spark plugs. I cleaned the throttle body and maf meter about 3 weeks ago. When the car was bone stock it had the same problem about 50% of the time.

 

[JeremyH]

Check the spark plug gaps.

 

[kytoploader]

Any other ideas on this? The spark plugs are new with .025" gap. I have 9psi of boost. The fuel pressure sensor went out last week. The sensor smelled like gas and set an engine code. I replaced it and the code went away. However, I'm still having a problem starting when hot. It sounds flooded when it first starts and also surges in the parking lot occasionally.

 

[dysan]

.025 gap is rather small for only 9psi of boost. My plugs are .029 and I've gone up to 15-16 psi with 11:1 compression.

I doubt it's your problem but whenever you replace those plugs you should really gap them .030 - .032 range at your boost.

Have you done any datalogging and discussed this with Brenspeed? Quite possible it's in the tune.

 

[kytoploader]

I did get another tune from Brenspeed that helped with the surging but not the hot start. It had the hot start problem when it was stock without the cams or supercharger. I'll increase the gap at the next plug change.

I probably need to clarify the problem. It cranks fast and has a new battery. It just doesn't fire up. It seems to start best after I crank, cycle the key off, and then crank again. Sometimes a second key off and crank sequence is needed.

 

[07 Boss]

Try turning the key to the on position and waiting a few seconds before actually turning it all the way to start. Let me know if that helps.

 

[Fullboogie]

Sounds like you may have a problem with the fuel system holding pressure after shutoff.

 

[AutoXRacer]

Yes, check your fuel pressure before cranking the motor. I had hard starting issues when the temperatures were hot in FL. The fuel temp rises so much that it causes vapors. The solution was to raise the fuel pressure as fuel temp rises. Solved my hot starting issues.

 

[Pentalab]

Try turning the key to the ON position and waiting a few seconds before actually turning it all the way to start. Let me know if that helps.

This. When I do that on my 2010 with M90 blower and 39 lb injector's etc, fuel rail pressure is 52 psi. Which drops to 40 psi with eng on. I had to leave it in the ON position long enough for the aeroforce gauges to boot up.

 

[AutoXRacer]

This. When I do that on my 2010 with M90 blower and 39 lb injector's etc, fuel rail pressure is 52 psi. Which drops to 40 psi with eng on. I had to leave it in the ON position long enough for the aeroforce gauges to boot up.

If you cycle the key a couple of times, you may get high pressures.

Does the motor start better when you build the fuel pressure in the rails?

 

[Pentalab]

If you cycle the key a couple of times, you may get high pressures.

Does the motor start better when you build the fuel pressure in the rails?

Mine starts up instantly, no need to leave key in 'on' position..or cycle the key a couple of times. I just did it as an experiment, since I read somewhere that the fuel rail pressure was 51-52 psi with key in 'on' position..and eng still off. They were correct. On a similar note, a friend of my son has to put the key to 'on' position for 2 secs before starting her chevy malibu..otherwise it won't start.