Problem starting engine warm!

[winstonwilliams]

I have a 502 fuel injected motor that has a hard time starting when warm. The motor starts right up when cold. If you run the motor for a while and then turn it off and start it right away it starts right up. But if you turn the motor off and wait anywhere from 10 mins to an hour you must give it full throttle and it will finally start after about 15 to 20 sec of cranking. Any ideas

Thanks

 

[winstonwilliams]

Re: Problem starting engine warm!

Oh yeah after the engine starts it runs great!

 

[Bigdave196]

Re: Problem starting engine warm!

Throttle Positioning Sensor?
or is your boat also equiped with a MAF?

 

[winstonwilliams]

Re: Problem starting engine warm!

If it was the throttle positioning sensor or the MAF wouldn't the engine hesitation or stumbling during acceleration or even have loss of power? Wouldnt there be some bucking and jerking, idle surging, engine cutting off, ect? The motor runs great other than not starting warm

 

[bigskiohio]

Re: Problem starting engine warm!

The coolant sensor acts like a choke

 

[winstonwilliams]

Re: Problem starting engine warm!

I was thinking that it might be vapor lock. Meaning that once the engine gets turned off the combination of the heat from the engine room and no air flow heats the gas lines and raised the temp of the gas while it sits in the gas lines so it changes states and turns from a liquid into a vapor. So the engine will not start. But once the throttle is opened and the engine continues to crank it finally gets new gas from the tank that is at a lower temp. Guess I could just open the engine compartment once the engine is stopped and put a fan on the engine while it sits... This should tell me if my theory is correct. What do you guys think?

 

[Bigdave196]

Re: Problem starting engine warm!

Vapor Lock only happens when you have seriously warmed the motor to almost overheating tempatures. I dont think a Fuel Injected motor can vapor lock, expecially on a boat. You usually dont have the rigiorus temperatures that you would sustain in an auto.

 

[Rocky_Road]

Re: Problem starting engine warm!

Vapor Lock only happens when you have seriously warmed the motor to almost overheating tempatures. I dont think a Fuel Injected motor can vapor lock, expecially on a boat. You usually dont have the rigiorus temperatures that you would sustain in an auto.

This is no longer true with the introduction of ethanol laced gas. Heat soak is a real issue with marine I/O's...enough of an issue that the boat manufacturers are trying to rethink the way they route the gas line.

I posted a boating magazine article about this problem some time back...I will try to locate it!

 

[winstonwilliams]

Re: Problem starting engine warm!

I have read that the ethanol lowers the boiling point of the gas, so the gas boils much faster.