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Chaparral1

Slow starting when warmed up.

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Why would my '07 VP 5.7 start immediately when cold but not when warmed up? It turns over more frequently before starting and doesn't 'ignite''.

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Vapor lock? Heat soak?

+1

Try running your blower more, I also open the engine hatch some during the day and let heat out, seems to help.

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Is the engine a Fuel Injected or a carburetor ?

Probably fi being that is an 07. Plus, don't fi engines tend to use a hotter thermostat?

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It is fi. Just replaced the fuel pump and o-rings due to the whining. Did I miss a step on the install? I did not replace the fuel pressure (sensor?) that's in-line atop the intake manifold.

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When I turn the key I hear 3 beeps then a short whine. When the whine stops I start the engine. Thought the whine was the pumps priming.

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That's what I hear on start up (5.0 GXi) and how I do it. Never had a problem with starting a warm engine, however.

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Not sure. But Wing nut can add to.

Old enough to have the injectors LEAKING DOWN after just running. That will make the cylinders so rich for a few seconds,that it can not even fire. Hondas have a built in 2 to 3 second of cranking WITH NO FUEL to sweep out any bleed down richness. Then it fires perfectly & smoothly.

When the no firing time ends. Does the engine start very briefly with soft sounding erratic firings for about 1 second ? Then go to a smooth idle ?

Good cold start ? Any bleed down fuel will vaporize and the excess that can not vaporize will have plenty of time to run down to the space between the cylinder wall & the piston wall.

But to get the above to happen would mean that all or most of the injectors are being held open after the key is turned to off.

If you stop with a hot engine. Wait say 3 to 5 seconds. Does it go thru the long cranking period ?

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Excellent cold starting - explodes to life. When warm The engine quietly comes to life - no explosion. Haven't noticed erratic firings. Going out Thurs - will verify and also look at 3-5 second shut down. Will a little rev upon shut down help? I shouldn't have to do that though.

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If the cranking is at normal speeds hot & cold ? Hopefully. That will eliminate a overheated engine. Like a sticking thermostat at too high of a temperature. ETC.

If it turns out to be no backfirings when hot restart. It really could be a STUCK choke . Computer controlled. The computer is always starting as if it thinks the engine is very cold. Chokes come off in steps of lessor & lessor degrees of choking over about 30 to 45 seconds.

A friend had a F I outboard engine. No choking on a cold start. Crank & fart. Crank & fart a few more times. Crank & fart many more times. ETC. Until it is warmed up enough to race the engine up for enough heat.

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If you have a coolant temp sensor giving a cold or cool reading all the time it can cause a warm/hot hard start. Possible cause could be buildup on sensor, faulty sensor or corroded terminal. I would remove sensor wire and check for loose terminal or corrosion then remove the sensor and check for any scale buildup. That is something you can do for free before you have it hooked up to computer.

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If it is a sticking choke ? 

 You could be running    RICH    all the time.  BAD NEWS.  Rapid carbon build up on the cylinder parts.   Get this problem found out fast.  Check the color of a couple of easy sparkplugs to reach. Going black ? You have a serious problem right now to fix.

 

Good luck.

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