Jim Grant's Tech Tips
'90 Plymouth Voyager, Fuel Pressure Test
Q: I just bought a 90 Plymouth Voyager with a 3.3L engine. It is fuel injected. I have it on jack stands. It misses at high RPM, as if it is starving for fuel. I have replace all the spark plug wires and the plugs are new. The fuel pump is supposed to be new. I have 60 psi of fuel pressure before the fuel filter and 18 after the fuel filter. I have replaced the fuel filter but the reading remains the same. What am I missing?
- Charles H.
A: I have to say you do have a confusing problem and the fuel pressure readings youve provided just dont add up. If you had a plugged fuel filter, the pressure readings you are reporting are possible. But, to have the same readings after replacing the filter with a new filter is just weird. Also, the engine would hardly run at 18 psi of fuel pressure never mind being able to drive the vehicle. At the top and front of the engine, there is a fuel pressure test port on the fuel rail for the injection system. With the fuel pressure gauge installed, you should see about 45 psi after cycling the ignition switch a couple of times to activate the fuel pump. With the engine running, you should see about 35 psi fuel pressure. If all you have at the test point is 18 psi fuel pressure as reported and 60 psi before the fuel filter, then there is a restriction/blockage in the line. When testing before the fuel filter be sure to tee into the fuel line to monitor the fuel system pressure.