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tarpon
08-07-2008, 11:22 AM
1998 Maristar with LT1 330 hp cold starts great.
After running for 30 minutes turned off engine, anchored up and swam around for 30 minutes.
Tried to start and engine bogged down and died then would not start.
Waited for 30 minutes and started right up.
This has been a problem for some time.
Any ideas or suggestions before taking into dealer would be helpful.

bigmac
08-07-2008, 11:47 AM
Sounds like vapor lock, although vapor lock in a fuel injected engine is rare (some would say impossible).

I guess the first place I'd start would be leaving the deck lid open after shutting down, keep the blower running, maybe insulate the fuel rails temporarily -- see if those things help. I would also change the fuel filter, and make sure the fuel pump is up to snuff.

tarpon
08-07-2008, 12:34 PM
Thanks-
one more piece of puzzle-
when engine is hot, engine will restart immediately after shutting off but after sitting for 30 minutes it will run rough and choke down upon starting.
How would tech duplicate problem to identify problem?

JimN
08-07-2008, 01:01 PM
Not vapor lock, heat soak. Open the motor box and let it cool before starting in hot weather. If you run it hard, let it idle for a couple of minutes before shutting it off. That and opening the motor box should make it easier to start.

tarpon
08-07-2008, 02:21 PM
Thank you for reply-
How does engine temp impact starting, if engine is thermally overloaded shouldn't engine light come on?

JimN
08-07-2008, 02:37 PM
It the coolant temperature sensor indicates >190F, it goes into RPM reduction, in order to keep the motor from running at high speeds and generating more heat. Some people call it "limp mode" or "limp home mode" but this should never be done with a boat. Cars have a closed cooling system and a radiator, most boats don't and if the boat motor keeps running with no coolant, it cooks, especially when it has aluminum heads, like an LT-1. The ECM toggles the injector banks in EPM reduction and if it runs really lumpy when this happens, it's likely that heat soak is the reason provided the impeller is good and there's no restriction on the raw water flow.

Check the impeller and oil cooler now. If the impeller is more than a couple of years old, while it may have all of its vanes, it's no longer good.

tarpon
08-07-2008, 02:46 PM
Many thanks again- will replace impeller and check intakes.

rob935
08-10-2008, 02:11 PM
it does sound like heat soak but may be the ignition module either , the symptoms for both are very similar as the module will break down under heat but work perfectly as it cools down but will get progressively worse as time goes on whereas heat soak will remain constant.