Fuel Pressure issue: Adice needed please
10-29-2014, 12:49 PM
#1
Senior Member
Thread Starter
Fuel Pressure issue: Adice needed please
At my wit’s end here and would appreciate some input.
I have a Weistec E55 with loads of supporting mods. The car is really strong but I have a lingering Fuel Pressure issue that for a very long time now has been hampering my enjoyment of the car. Hope some of the experts here have some useful ideas and will chime in.
On the fuelling side, I’m running 2 AEM 320 lph pumps with the stock (brand spanking new) fuel sender unit, stock fuel lines, Weistec’s fuel rails (larger diameter than the stock rails) and Weistec’s 650cc injectors. I have new fuel relays, a new CPS and a new cam positioning sensor fitted.
I’m measuring fuel pressure via the DashDAQ. Although it’s not properly calibrated, I can gauge with enough certainty from the fluctuations in FP readings what’s happens to FP in different situations. So at idle, the DashDAQ will read at around 6.2 which equates to about 5.3 bar. On a WOT run, when the FP issue is not present, the DashDAQ reading will fall to a low of around 5 which equates to about 4 bar.
The issue: The issue is more likely to arise in hot weather than cold, when the tank is closer to empty than full and when I’ve been driving for longer periods than shortly after start-up.
When the issue arises, FP will drop off dramatically under hard acceleration, For e.g. on a short WOT burst, FP will quickly fall to low 3s and I’ll immediately come off the gas. I’m sure that if I stayed on the gas, FP would fall away altogether (and my rebuilt motor would go boom in the process).
If, after the issue has arisen, I cruise at moderate speeds, FP will usually hold-up but the moment I get on the throttle, it falls quickly to dangerously low levels. The issue will resolve itself if I park the car and allow it to cool for a period. The cool-off period required varies. Leaving the car overnight will always resolve the issue. Sometimes leaving it parked for an hour or two will suffice.
Heat is clearly a factor. The fuel rails are extremely hot to the touch, even after a short (5km) drive first thing in the morning. I’ve tried heat-wrapping the fuel lines but no improvement. My mate who’s trying to help with this thinks that when the issue arises, either the pumps begin to cavitate or the fuel starts percolating in the fuel rails. We have no idea why either of these scenarios would occur.
Any suggestions/input welcome, thx
I have a Weistec E55 with loads of supporting mods. The car is really strong but I have a lingering Fuel Pressure issue that for a very long time now has been hampering my enjoyment of the car. Hope some of the experts here have some useful ideas and will chime in.
On the fuelling side, I’m running 2 AEM 320 lph pumps with the stock (brand spanking new) fuel sender unit, stock fuel lines, Weistec’s fuel rails (larger diameter than the stock rails) and Weistec’s 650cc injectors. I have new fuel relays, a new CPS and a new cam positioning sensor fitted.
I’m measuring fuel pressure via the DashDAQ. Although it’s not properly calibrated, I can gauge with enough certainty from the fluctuations in FP readings what’s happens to FP in different situations. So at idle, the DashDAQ will read at around 6.2 which equates to about 5.3 bar. On a WOT run, when the FP issue is not present, the DashDAQ reading will fall to a low of around 5 which equates to about 4 bar.
The issue: The issue is more likely to arise in hot weather than cold, when the tank is closer to empty than full and when I’ve been driving for longer periods than shortly after start-up.
When the issue arises, FP will drop off dramatically under hard acceleration, For e.g. on a short WOT burst, FP will quickly fall to low 3s and I’ll immediately come off the gas. I’m sure that if I stayed on the gas, FP would fall away altogether (and my rebuilt motor would go boom in the process).
If, after the issue has arisen, I cruise at moderate speeds, FP will usually hold-up but the moment I get on the throttle, it falls quickly to dangerously low levels. The issue will resolve itself if I park the car and allow it to cool for a period. The cool-off period required varies. Leaving the car overnight will always resolve the issue. Sometimes leaving it parked for an hour or two will suffice.
Heat is clearly a factor. The fuel rails are extremely hot to the touch, even after a short (5km) drive first thing in the morning. I’ve tried heat-wrapping the fuel lines but no improvement. My mate who’s trying to help with this thinks that when the issue arises, either the pumps begin to cavitate or the fuel starts percolating in the fuel rails. We have no idea why either of these scenarios would occur.
Any suggestions/input welcome, thx
