odd fuel psi problem ?? HELP
Thread Starter
Keep The Shiny Sine Up
Joined: Mar 2006
Posts: 135
Likes: 4
From: Dublin California
odd fuel psi problem ?? HELP
well this is NOT a issue at full throtel
this happens even if you blip the throtel
at idle i have 60 lbs psi
if i give it some gas the gauge drops 5-7 lbs
then right back to 60
if i hit the gas real hard and firm it will drop to 45 lbs psi and then creep up to 53 ish
i have put a new racetronix harness in thinking it might be the problem
checked all conections ok
i have been through 2 racetronix fule pumps
they fail after a few hunderd miles
i thought i found the problem i had a MSD boost a pump installed
and at idle it was giving 17 volts and under boost it was way higher
the adj trim had no effect
so off to the junk pile it went
and a kenny bell went in
well still having the same up and down in psi
not even hitting boost
i now have a bosch 420 in tank pump
and same old problem
i have changed the filter/regulator
twice
i thought the gauge might be the problem
so a new gauge and sender went in same thing still jacked up
what am i missing
any help on this ?
this system did work at first about 700 miles ago then all went bad
thanks
this happens even if you blip the throtel
at idle i have 60 lbs psi
if i give it some gas the gauge drops 5-7 lbs
then right back to 60
if i hit the gas real hard and firm it will drop to 45 lbs psi and then creep up to 53 ish
i have put a new racetronix harness in thinking it might be the problem
checked all conections ok
i have been through 2 racetronix fule pumps
they fail after a few hunderd miles
i thought i found the problem i had a MSD boost a pump installed
and at idle it was giving 17 volts and under boost it was way higher
the adj trim had no effect
so off to the junk pile it went
and a kenny bell went in
well still having the same up and down in psi
not even hitting boost
i now have a bosch 420 in tank pump
and same old problem
i have changed the filter/regulator
twice
i thought the gauge might be the problem
so a new gauge and sender went in same thing still jacked up
what am i missing
any help on this ?
this system did work at first about 700 miles ago then all went bad
thanks
Instructor
Joined: Feb 2005
Posts: 228
Likes: 2
From: Phoenix AZ
St. Jude Donor '08
Have you checked the fuel pressure at the rail with a mechanical guage or with a dyno? I've had problems with 2 fuel pressure guages/sensors. Always reading low compared to the dyno. Have installed like you upgrades including Walbro 255 fuel pump, racetronic wiring harness and KB BAP just to be sure. Gauge is still low by 8-10 psi compared to two different dynos showing a solid 60psi. I thought maybe I wired it wrong. Or something with the sensor wires to the guage. But all seems to check out ok as far as I can tell. I was hoping someone could tell me what the voltage should be coming off the sensor at 60psi but never got an answer from the manufactuer. So unfortunately right now my fuel guage doesn't tell me much.
Thread Starter
Keep The Shiny Sine Up
Joined: Mar 2006
Posts: 135
Likes: 4
From: Dublin California
i have not checked it with a mechanical gauge as of yet
i did replace the after market one just a few days ago
and it had the very same readings
what realy stumps me is that it was rock solid around 700 miles ago
and now it is all over the scale
i have also ( for testing ) went back to the stock harnes and it too has the same readings
im starting to think it might be in the p c m
but im just guessing
any way
thanks
i did replace the after market one just a few days ago
and it had the very same readings
what realy stumps me is that it was rock solid around 700 miles ago
and now it is all over the scale
i have also ( for testing ) went back to the stock harnes and it too has the same readings
im starting to think it might be in the p c m
but im just guessing
any way
thanks
Drifting
Joined: Aug 1999
Posts: 1,278
Likes: 0
From: Amelia ohio
Did you put a new Sock (filter) on the fuel pump?
I changed mine along with the fuel filter and the fuel pressure was much better, but still drops down lower than I think it should.
The fuel filter had just a few miles on it, but I was using race fuel and it seems to mess up the filters. I'm going to run a larger line to the fuel rail to see if that helps.
I changed mine along with the fuel filter and the fuel pressure was much better, but still drops down lower than I think it should.
The fuel filter had just a few miles on it, but I was using race fuel and it seems to mess up the filters. I'm going to run a larger line to the fuel rail to see if that helps.
