swift13 Posted May 10, 2010 Report Share Posted May 10, 2010 my 98 gtp has gotten a new fuel pump, new fuel filter, new fpr, and new vacuum lines from the fpr to the map. but i still have a drop in pressure after the car starts and will only run for a minute before it bogs out due to lack of pressure. with the pressure gauge on it reads around 40 psi at start and slowly drops off until it dies then once it dies out the pressure shoots back to 40. im kinda stumped here, as my only other guess is that the fpr is still no good, could it be the map sensor or possibly the computer? any suggestions would be great thanks. Quote Link to comment Share on other sites More sharing options...
BXX Posted May 10, 2010 Report Share Posted May 10, 2010 Check the wiring at the tank. Often i've seen high ground resistance due to a loose connection at the connector. Also, make sure its getting proper voltage, check for voltage drop as well. Could have corroded connection somewhere. And I dont know much about the dual speed fuel pump wiring, but maybe an issue with the resistor failing? Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 10, 2010 Author Report Share Posted May 10, 2010 Changed the harness for the pump. You have to. Didn't check voltage cuz it seemed if it was going back up once the car died it wouldn't be voltage Quote Link to comment Share on other sites More sharing options...
BXX Posted May 10, 2010 Report Share Posted May 10, 2010 Did the issue start after you replaced the pump?? Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 10, 2010 Author Report Share Posted May 10, 2010 No. Already had the same issues figured the pressure drop was bad pump Quote Link to comment Share on other sites More sharing options...
BXX Posted May 10, 2010 Report Share Posted May 10, 2010 IIRC your pressure on KOEO should be around 50psi or so.. Possible restricted or kinked fuel line? From the sounds of it the PCM is cycling the fuel pump for a few seconds its supposed but after that the primary circuit that keeps it powered after that isnt working properly. When it dies, the PCM is cycling the pump again, hence the pressure increase.. Ill need to look at the wiring for it to know what all is involved in it. If nobody had any help for you by tomorrow evening when I get home from work, I can pull up the wiring diagrams and give you an idea of what to specifically look at. Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 10, 2010 Author Report Share Posted May 10, 2010 Sounds good thanks Quote Link to comment Share on other sites More sharing options...
AL Posted May 10, 2010 Report Share Posted May 10, 2010 i am wondering if your oil pressure sending unit is shorting and not telling the fuel pump to keep running... Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 10, 2010 Author Report Share Posted May 10, 2010 is there any way to check for that Quote Link to comment Share on other sites More sharing options...
AL Posted May 10, 2010 Report Share Posted May 10, 2010 Im not sure how you would check that Quote Link to comment Share on other sites More sharing options...
Nick1234 Posted May 10, 2010 Report Share Posted May 10, 2010 i would almost wonder if the maf is bad. Sounds similar to what my cousins car was doing when his Maf went Quote Link to comment Share on other sites More sharing options...
Addicted2bass Posted May 10, 2010 Report Share Posted May 10, 2010 i am wondering if your oil pressure sending unit is shorting and not telling the fuel pump to keep running... This happened on a 87 Park Ave i had. Oil pressure switch went bad and was shorting out the fuel pump, kept blowing the fuse. Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 10, 2010 Author Report Share Posted May 10, 2010 all fuses and relays are good. checked underneath for the oil pressure and there are 2 of them, one on each side of the oil pan. wonder what thats about. my big concern is that if it were any type of sensor wouldnt it read on the computer, i show no codes. maf sensor i dont think would cause the drop in pressure in the fuel but once again woulndt that bring an ses ight Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 12, 2010 Author Report Share Posted May 12, 2010 For anybody wanting to know it ended up being the computer, i went to the yard and pulled one off a 98 se 3.8 and threw it in my car and bingo problem solved Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 13, 2010 Author Report Share Posted May 13, 2010 ok so i found out in the process that i need a gtp computer for the s/c to work (or at least the boost gauge) can i pull the chip from my old one or no? Quote Link to comment Share on other sites More sharing options...
BXX Posted May 13, 2010 Report Share Posted May 13, 2010 There is no chip to pull... the PCM has flashable internal memory You need S/C PCM period. I dont believe you can just flash the N/A PCM to S/C coding and have it work right. I also though some of the PCM outputs/wiring as a tad different but I could be wrong on that Quote Link to comment Share on other sites More sharing options...
swift13 Posted May 13, 2010 Author Report Share Posted May 13, 2010 When I looked up the part number it was matching for the year could be an se gt or gtp all had the same number as long as it was a 3.8 but it said it would need to be flashed. I'm assuming I can get this flashed to work right but do I need to go to the dealer for that? The car is running just fine but I noticed no boost gauge in the dic Quote Link to comment Share on other sites More sharing options...
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