russian rocket Posted July 9, 2017 Report Share Posted July 9, 2017 Hey guys, my buddy has a 2007 gt500 with a strange issue. Its heavily modded and makes just north of 800whp. recently the car developed a crank no start issue. but it is intermittent and i am having a hard time tracking down the issue. the problem started recently, the car was stumbling a little bit and then when he shut it off, it wouldnt start back up. if you waited 15-20minutes it would start just fine and run with out issues. the problem has progressively gotten worse and now the car hardly ever starts. I did some trouble shooting and realized that the fuel pumps were not kicking on. There was only about 5.6v going to the KB BAP and same coming out of it to the fpdms. This voltage was checked as soon as the key was turned to the on position. While fuel pressure was never verified with a mechanical gauge i never heard the two walbro pumps kick on and the fuel pressure PID showed low fuel pressure. We tried several things like checking fuse and relays. i ohmed tested most of the wires that go to the fpdm's from the pcm. every once in awhile, it would start back up when we messed with it but as soon as we turned it off, it would not start again. We did unplug the driver side fpdm at one point and the car fired right up, idled smoothly and even restarted several times. so great we figured that fpdm was bad. so he bought a new one and the problem still persists and unplugging the fpdm doesnt have the same effect as it did last time. I am kinda stumped, im guessing there is a wiring issue somewhere, but not really sure where to look. I know some of these cars had issues with water getting into the passenger side kick panel and causing weird issues, we are going to look into it tomorrow. is there anyway to trouble shoot the KB BAP, when the proper voltage goes to the BAP, the output voltage is ~21v. so it seems to be working correctly, i just dont know if maybe its starting to fail and causing this issue that we are experiencing. Quote Link to comment Share on other sites More sharing options...
iwashmycar Posted July 10, 2017 Report Share Posted July 10, 2017 Is there a fuel filter(s)? Just thinking easiest option first lol Quote Link to comment Share on other sites More sharing options...
russian rocket Posted July 10, 2017 Author Report Share Posted July 10, 2017 Is there a fuel filter(s)? Just thinking easiest option first lol we can definitely check it, but man at less than 20k on the clock something like that doesnt even cross my mind lol Quote Link to comment Share on other sites More sharing options...
aussiek2000 Posted July 10, 2017 Report Share Posted July 10, 2017 what's fuel rail pressure? Those BAPs are incredibly hard on fuel pumps. Quote Link to comment Share on other sites More sharing options...
iwashmycar Posted July 10, 2017 Report Share Posted July 10, 2017 we can definitely check it, but man at less than 20k on the clock something like that doesnt even cross my mind lol but 10 years! Quote Link to comment Share on other sites More sharing options...
russian rocket Posted July 10, 2017 Author Report Share Posted July 10, 2017 Well guys I think the problem has finally been resolved. Spent about 5 hours on it today testing components, running down wires and testing wires. In the end, word of advice to all mechanics, remove/retrieve your tools after you are done working on the car. That tool was clamped on to this ground wire and must have been grounding out against the engine. It was hanging very low in there and it was a pain to remove. but once removed the car fired right up and continued to do so several times after that. Two other issues were resolved too. Owner had issues with his sct tuner and obd code reader not always connecting. That ended up being a pin in the obd harness that was to far open so I closed it a bit and now that's fine. A recent problem developed where his cooling fan wasn't turning on, that ended up being a melted harness plug right at the fan. Quote Link to comment Share on other sites More sharing options...
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