4evervette

HI guys

i hope some one should know the answer to this and can hep me out ..

this car with 408 engine A4 trans ..42 lb injectors...with high mileage

on the dyno after it pass 4000 rpm the fuel press drops down to 40 psi and as soon the it pass 4k rpm AFR goes lean to 14

that was its own stock fuel pump ..pump 1

so we changed it to wallbro fuel pump ...again to the dyno same thing fuel press drops and afr leans out ..pump 2

so we change again to stock NEW fuel pump same problem with the fuel pressure but this time AFR stays where its commanded 11.7..pump 3

injector duty also around max 70%

any suggestion as what could be the problem...

thanks

btw we check the fuel pressure on the dyno reading and with mechanical gauge ..

ND400

Faulty FPR. Any rubber fuel hoses could be getting sucked in under pressure

4evervette

as far as the regulator we changed it with new one when we replaced the whole assembly pump.....

..how shall i check for the fuel hoses..


could it be the car need more fuel ??!! coz it didnt make any hugh numbers we expected higher number but only 400rwhp 410 rwtq..