96 disco 150K

Have been having an intermitent problem with a rough idle following start up. No problem starting but just after. It will stumble and sputter and I can manage to rev it out.

I have changed plugs and leads. The problem is mostly when hot but not always. I disconnected the fuel temp sensor and problem was still the same.

I have removed the fuel rail valve and placed a clear hose on the stem to measure fuel volume. When energised the pump will run for several seconds and produce about8oz of fuel then i can hear the relay disconnect. I ran it several times.

can anyone tell me if this is normal for the pump to run only that long. Obviously there is no back pressure on the pump so i thought that might be a problem.

No fault codes other than O2 sensor but i've put up with those for 50K.

Any help appreciated

Adrian

 

#1 suspect is the fuel temp sensor.
Next would be a dirty intake, idle control valve or cheap gas.

 

your fuel pump operates solely based on flow and resistive pressure. If the flow is blocked it will pump slowly, producing less volume in a given time and will take longer to reach its set cutoff pressure... once the pump has reached its set pressure in a closed system (ie. ignition on, engine stopped). You should have about 30 psi at the rail. and it shouldn't cutoff with your measurement test (open system).

If your system exceeds that 30 psi the fuel pressure regulator returns the exces fuel to the tank. When you disconnect the FTS you mimick a nonworking sensor... my guess is that you would not see a difference.

I'm votin for either the FTS or the Idle air control valve since this problem only happens at initial idle... and based on your mini tuneup.

 

Thanks for the input.

Just to cover the fuel pump...do you think there is a problem with the pump if it will not run continuously without shutting off in an open system?

Is there a way to test the idle air control valve and the FTS?

Thanks again.
Adrian

96 Disco 150K

 

The fuel pump will only run for a few seconds unless the engine is running.
This is normal.

 

Hey bonzadesign, did you figure this one out? I am having a very similar issue with my 98 disco 1. The only difference is it seems to idle more roughly if I'm parked on an incline with the front going up-hill.