maybe the regulator isnt regulating...
I have a 1997 Jetta GLX with the 12v VR6. When I measure the fuel pressure at the injector rail I see 34 PSI, which rises to 44 PSI when I disconnect the vacuum line to the fuel pressure regulator. I tested fuel pressure at the fuel pump and find 96 PSI. I removed the (original equipment) fuel filter and found it to be pretty restricted (very scientifically -- I tried to blow through it) so I replaced it with a new one. This made no difference at all to my fuel pressure measurements -- I'm still seeing 34 PSI at the injectors when the Bentley says I should see 51 PSI at idle.
Is 96 PSI a good reading at the fuel pump?
What else might be plugged/kinked between the fuel filter and the injector rail? I don't see any issues with the fuel hoses.
I don't see a spec in the Bentley about pressure at the pump. However, I did just run the fuel delivery test and found just under 700ml fuel delivered in 30 seconds, with 10.9v across the pump terminals while running.
The book's graph says to expect 725-845 ml at 10.9v
I think I need a new pump :-(
I have been working slowly at this over the last several weeks. I have:
- found fuel pressure at the injector rail to be ~34 psi rather than 51 psi the Bentley recommends
- replaced the fuel pressure regulator; no change in fuel pressure as measured at the injector rail
- replaced my 15 year old fuel filter (no change in fuel pressure resulted)
- measured fuel flow rate over 30 seconds; I found just less than 700ml when the Bentley calls for at least 725ml.
- replaced fuel pump, again with no change in fuel pressure
The fuel pump creates a static pressure of almost 100 PSI when I route the pump output directly to the pressure gauge, so I know the pump generates lots of pressure. The fact that the pressure is low at the injector rail leads me to think the fuel is leaking out of the supply lines either to the ambient, into the engine, or into the return line to the tank. I don't think it's leaking to the outside since I have no fuel smell or visible leaks.
Can the injectors leak in some fashion that would allow enough fuel to escape to let the injector rail pressure fall ~17 psi?
Has anyone seen a way in which fuel could leak around/past the fuel pressure regulator into the fuel return line?
I'm having trouble thinking of where the fuel could be going.