GMC Posted May 16, 2012 Share Posted May 16, 2012 Got a strange problem........ Start the car and fuel pressure sits perfect at 37psi and will remain the same for ever if I left the car ticking over. Drive the car and over a mile or so the pressure drops to a point the car is undriveable, to around 15psi. it'll continue to tick over at 15psi, but the pressure won't rise again until the car is stopped, fully cooled down and then the same scenario happens again? I've replaced the following; Fuel pump (twice - brand new Bosch pump fitted now), pressure regulator, filter, supply fuel line. I've also checked the tank breather - all fine (no vacuum) The only part of the fuel system I've not replaced is the return line, but dont see how this could be linked. Anyone came across a similar problem? Cheers Quote Link to comment Share on other sites More sharing options...
Kevin Abbott Posted May 16, 2012 Share Posted May 16, 2012 A long shot, have you got your input and return lines crossed over where they come through the inner wing? So it's pulling fuel from the return? Quote Link to comment Share on other sites More sharing options...
GMC Posted May 17, 2012 Author Share Posted May 17, 2012 Cheers Kevin, but thats ok. Like yourself it was one of the first things I checked Another thing I should have mentioned... No fuel leaks & new injectors Quote Link to comment Share on other sites More sharing options...
opelmantagsi Posted May 17, 2012 Share Posted May 17, 2012 (edited) have seen same problem on Calibra's over here and they all turned out to be perished hoses, no evidence of fuel leaks, but same symptoms are you describe new fuel lines and problem solved. Edited May 17, 2012 by opelmantagsi Quote Link to comment Share on other sites More sharing options...
GMC Posted May 17, 2012 Author Share Posted May 17, 2012 Thanks again, but all new hoses fitted. What I don't understand is why the problem only occurs when the car is driving as the delivery of fuel remains the same. When under load, it simply returns less to the tank. Quote Link to comment Share on other sites More sharing options...
opelmantagsi Posted May 17, 2012 Share Posted May 17, 2012 (edited) same symptoms turned out to be a pin hole in a hose Edited May 17, 2012 by opelmantagsi Quote Link to comment Share on other sites More sharing options...
jasper Posted May 17, 2012 Share Posted May 17, 2012 Possibly fuel pump relay breaking down,had a similar fault with an astra gte we had years ago. Quote Link to comment Share on other sites More sharing options...
tony g Posted May 29, 2012 Share Posted May 29, 2012 I would suspect the fuel pressure regulator on the fuel rail. It may have a weakened diaphragm which gets worse when hot. This reg is what determines how much fuel is to be returned to tank, so if the return line is blocked for example the pressure would be high. In normal use when the reg sees vacuum (low load part throttle) the reg is open more to allow the pressure to escape to tank. When on full power (or getting near it) the vacuum in the manifold all but disappears the reg is more closed allowing more pressure to be maintained. A quick test to see if there are any changes would be to disconnect the vac pipe from the reg and block it (to avoid air leak). The pressure at idle "should" increase over what it was before with the pipe on. Drive it like this to see if the pressure drops the same. If you see a noticeable difference i would change the reg to a known good one. hth tony Quote Link to comment Share on other sites More sharing options...
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