09SVT500 Posted April 15, 2011 Report Share Posted April 15, 2011 new memeber here and i have a quick question. my car ( 2009 GT500) has a hard time starting when it is hot. when the car is cold is fires instantly as any other car would but when the car is up to temperature and you shut it down it has a hard time starting back up. the car has done it since it was stock and now has a pulley + jlt and tune. when it finally does start there is a very strong exhaust odor (smells very rich) but only upon start, once running it smells fine (dyno proves the car isnt running rich). we cant seem to figure out what would be causing it to start hard and ANY ideas/theories would be apprecited. its almost as if the car is flooding itself out when hot. thanks for the help guys! Link to comment Share on other sites More sharing options...
socalwrench Posted April 15, 2011 Report Share Posted April 15, 2011 Is the tune stock? OBD II cars will run in open loop when they are cold, which will have a slightly rich mixture. When it's warmed up, it wll run in closed loop and adjust the fuel mixture accordingly. Since I understand you're issue happens when it's hot, it makes me believe that the current tune is adding too much fuel during closed loop operation. A small amount extra isn't a big deal with the engine running, but could cause trouble upon starting. Another idea, could be a vapor lock type of situation, where the fuel begins to vaporize before being injected into the engine. Does the issue occur more when the tank is low? Link to comment Share on other sites More sharing options...
09SVT500 Posted April 16, 2011 Author Report Share Posted April 16, 2011 The tune is not stock anymore but has done it since it was stock. The car does seem to do it slightly more when the tank is low but not significantly. It's more a heat issue. All the gauges read normal though. The car just seems to throw to much fuel in when starting when it's hot Link to comment Share on other sites More sharing options...
09SVT500 Posted April 16, 2011 Author Report Share Posted April 16, 2011 The tune is not stock anymore but has done it since it was stock. The car does seem to do it slightly more when the tank is low but not significantly. It's more a heat issue. All the gauges read normal though. The car just seems to throw to much fuel in when starting when it's hot Link to comment Share on other sites More sharing options...
socalwrench Posted April 16, 2011 Report Share Posted April 16, 2011 Hmmm... does it happen more when the weather is hot? Link to comment Share on other sites More sharing options...
09SVT500 Posted April 16, 2011 Author Report Share Posted April 16, 2011 yes the hotter it is outside the hotter the car is so in turn it has a harder time starting. the car is going in for its 20k service soon and i just want something to tell the mechanics to check Link to comment Share on other sites More sharing options...
socalwrench Posted April 17, 2011 Report Share Posted April 17, 2011 It's tough to say without having the car here, but fuel vapors could be causing the problem. Or, the extra heat is causing more electrical resistance (in the battery and wiring) and reducing the voltage available to the starter. Link to comment Share on other sites More sharing options...
09SVT500 Posted April 18, 2011 Author Report Share Posted April 18, 2011 I dropped the car off at the dealership today, I tol them to keep it as long as necessary to fix it. I just broke my ankle and the car was my DD so as of now I can't drive it anyway so it was good timing for me just tongi ahead and let them have it. I'll keep you updated with the feedback they give me (it's always nice to have a second opinion because the mechanics around here usually just try and push things under the rug) thanks for all the help guys! Link to comment Share on other sites More sharing options...
07SGT4578 Posted April 18, 2011 Report Share Posted April 18, 2011 I have a 2005 F-350 with a 5.4 that does the exact same thing. They told me it was the cats, so I cut them off. It STILL does it. Let me know what they find. Chris Link to comment Share on other sites More sharing options...
09SVT500 Posted April 20, 2011 Author Report Share Posted April 20, 2011 I haven't picked the car up yet, but I talked to the dealership and they said it was the fuel pump. I pick the car up tomorrow and I'll know for sure then. Link to comment Share on other sites More sharing options...
SPEEDY168 Posted April 20, 2011 Report Share Posted April 20, 2011 My agency has replaced several fuel pumps in our Crown Vics for the same reason. Link to comment Share on other sites More sharing options...
09SVT500 Posted April 22, 2011 Author Report Share Posted April 22, 2011 Hey guys quick update, i picked the car up today and sure enough it was th fuel pump, the car starts up perfect now. Dealership replaced it under warranty but if you car is out of warranty watch out as it is VERY expensive Link to comment Share on other sites More sharing options...
socalwrench Posted April 23, 2011 Report Share Posted April 23, 2011 I think the GT500 pumps are $700 alone. Glad to hear the problem is fixed. Link to comment Share on other sites More sharing options...
09SVT500 Posted April 25, 2011 Author Report Share Posted April 25, 2011 Its great to have to car up and running well again. Another benefit that no one was expecting is the fuel mileage has skyrocketed! I was averaging (before i had it fixed) 13.5 mpg when the tank was empty (i drive 90% city) and now my last tank of gas was 19 mpg! same driving conitions/styles. for a car that makes 540 WHP to average that was pretty exciting haha Link to comment Share on other sites More sharing options...
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