Car hard to start or won't start when HOT...

Boozshey

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Okay, so as many know, I am now rolling in a 5.8L short block, with 5.4L heads, and a 3.6L KB in my 05 GT.

When I got the car back together last year after the last build it ran good. I tracked the car, sent data logs to John Lund for tuning. The car ran beast.

I have since added a pulley and that's all. The datalogs still looked good and no changes were made.

The car from the begining had a hard time starting when hot, but always started after a few cranks. (when cold it fires right up.)

Fast forward to about a year and 4000 miles later. The car is being a bitch, I am constantly getting random mis fire codes and when the car is hot it will not start at all. I have to let it sit for more then 30minutes before it will start again.

I haven't checked the injectors yet and honestly don't really know how or what to check and it was mentioned that I might be getting the gas tank to hot from the exhaust, since my muffler exits presently to the gas tank. However, it's been that way for a while without a problem.

So this problem just crepted up and started without anything really being changed...

I have changed the plugs, double checked the plugs gap, looked at the coil packs, did a complete smoke down leak test and there were no leaks.

I guess short of running the car hot and datalogging again I don't know what else to check or what else it could be. :/

Anyone have any ideas. :helpme:
 

killr3v

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Could the injectors be leaking? Fuel will puddle and cause hard to start
 

Boozshey

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Nah, tired of emailing stuff to people. Honestly I have had 4 email tuners over the years. I'm the last person to get annoying and bug tuners over and over like some reports. Hell this problem has been going on for a few months and I've just been dealing with it. But it always seems after 3 emails to the web based tuners they stop replying to you. Just my experience.... Hell john ignored 3 requests for a damn gear change and my tune file is locked out and can't change it myself.

I was hoping to take care of the issue myself. I have a local guy that I can use and trust. But again I'd like to get it taken care of myself if I can. Then if I can't do it rely on someone else and pay then for work I can't do myself. I hate paying for shit I can do myself ya know.

I might just pull the injectors and send them back to the guy I bought them from. He's a big injector guy and is only in GA so shipping should be quick. :/
 

86GT351

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Nah, tired of emailing stuff to people. Honestly I have had 4 email tuners over the years. I'm the last person to get annoying and bug tuners over and over like some reports. Hell this problem has been going on for a few months and I've just been dealing with it. But it always seems after 3 emails to the web based tuners they stop replying to you. Just my experience.... Hell john ignored 3 requests for a damn gear change and my tune file is locked out and can't change it myself.

I was hoping to take care of the issue myself. I have a local guy that I can use and trust. But again I'd like to get it taken care of myself if I can. Then if I can't do it rely on someone else and pay then for work I can't do myself. I hate paying for shit I can do myself ya know.

I might just pull the injectors and send them back to the guy I bought them from. He's a big injector guy and is only in GA so shipping should be quick. :/

Understood. There is a place in Hobe Sound that has very reasonable prices for Injector testing and Flowing.
 

G.T

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Crank it for a few seconds with the accel pedal to the metal.. this should shut off the injectors allowing you to clear out the combustion chambers and rule out a fuel injector leak mentioned above
 

JeremyH

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Is it cranking fine just not starting when hot? When its hot is the motor hard to turn over by hand?
 

Boozshey

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I've done the mash the petal trick and it has worked a few times in the past. The last time no luck and I killed the battery.

For Jeremy.... Yes, always cranks fine and hard. Well until I kill the battery. Never tried to turn the motor my hand when it's hot. I suppose I can try it. What will that prove/disprove?
 

JeremyH

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Maybe clearances are tight enough to slow the motor down when hot such that its hard to fire up via the starter. Just a thought.

Hopefully its something simple. Doubt its a leaking injector it would be the other way around and harder to start cold.
 

Boozshey

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Well it's a stock 5.8l short block out of a 2013 gt500. I don't think the clearances would be bad?
 

JeremyH

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I've seen weirder things happen. Hard to warm start is an odd issue for sure. Is it tuned to stay in open loop?

So never any issue at cold start, just warm?
 

Boozshey

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Never ever had a cold start issue. Hell it gets half a crank and it starts. Warm starts have always been a problem. I've been in the line at the track and thought it wasn't going to start. Luckily it did, but a couple weeks ago, it was done, had enough I guess and just didn't want to start.
 

VectorPat

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Not sure if this relates but winter blend fuels have a lower boiling point than summer blends. Is it possible that you are getting the fuel too hot in the tank from your exhaust? We should be getting summer blend by now, just wondering if it might get a little better using it.
 

psfracer

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Yeah, i was just going to mention that---if it does it when hot only, on an old car it almost sounds like a fuel/vapor lock issue.

If you can turn over the engine with the starter until the battery dies, then obviously its not the starter. So what is left? Air, spark, and fuel. Air should be good because as you say, the motor turns over fine with the starter. Spark, easy way to test that by pulling a COP while turning over the motor to see if it sparks to ground. So fuel---it only when hot I would check everything with your fuel system, even the lines, etc.
 

JeremyH

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What is the fuel system? The frps has a temp sensor as well and the pcm will raise pressure to prevent the fuel from boiling when it gets hot.
 

psfracer

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Then could that sensor be faulty? I don't know, just throwing things out there.
 

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