Vince
New Member
hi i have a 99 gt it has an MMR 2v long block TF heads - KB 2.6 mammouth kit- gear star4R70 - 03-04 cobra fuel tank and fuel pump with polmaxracings - 2 new genuine walbro TI 255LPH gt supercar fuel pump upgrade kit for 03-04 cobra SVT terminator .car had the cobra fuel tank and pump in it with the stock pumps for 2years befor i did the rebuild with no issues . tuning started with stock cobra pumps and kb boost a pump fuel pressure started out fine slowley creep up till pump failed . bought another (carter) cobra fuel pump . ran car fuel pressure kept climbing . disconected boost a pump have big pully on supercharger and low compression motor only making about 6lbs of boost this helped finished full pull tuning car off dyno idling and fuel pressure went way high poped the frps and the pump agian returned the pump agian got the polemax kit . thought i was good with the walbros. cold tuning almost done and fuel pressure went up agian trigering the pressure relife vavle in fuel pump .any one have an ideal why fuel pressure keeps going up . (at start up fuel pressure is just under 30 psi as car warms up driving it creeps up to 40 then after driving for 40 minutes it was at 50psi got to tuner shut car off he took car out to fine tune thats when pump relife vavle released .the pumps say relife vavle start to open at around 70psi fully open at 87psi (walbro - F10000302)
