04 LX - Fuel Pressure Test

Posted by: DKH

04 LX - Fuel Pressure Test - 07/19/21 09:48 PM

I just tested the fuel pressure on my 04 (150K) and I have a question.

Key "on" the pressure is at 40psi, bottom end of the normal range. Engine running the pressure drops to and stays at 30psi, 10psi below bottom end of normal range. The hold pressure is within spec.


The car is running slightly rough but not throwing any codes.

Is this definitely a replace the pump situation, or is there something else that I should be checking that could affect fuel pressure other than the pump?

Thanks!
Posted by: dixiebandit69

Re: 04 LX - Fuel Pressure Test - 07/19/21 10:47 PM

With the engine running, pull the vacuum line off of the fuel pressure regulator.

It should pick up to 40 psi or so.

If not, probably new fuel pump time, or maybe time for a new fuel filter. Or a new fuel pump relay.

Maybe all three.
Posted by: RF_Overlord

Re: 04 LX - Fuel Pressure Test - 07/20/21 12:19 AM

KOER FP should be 40 lbs, not 30. I've not measured it KOEO. Only time I've ever seen mine read differently was when I drove to the supermarket and the car sat in the hot sun for a while. When I came out and started it, FP was 51 lbs and as I drove home (about 4 miles) the pressure slowly dropped back to 40. I assumed this was the fuel strategy to prevent vapour lock.
Posted by: DKH

Re: 04 LX - Fuel Pressure Test - 07/20/21 06:27 PM

Thanks for the suggestions.

With the engine running, I did pull the vacuum line off the fuel injector pressure sensor (mine does not have an actual fuel pressure regulator) and there was no change in fuel pressure. This has me wondering if the sensor is bad, but I'm not going to run out and replace it unless I'm sure, as it costs over $100.

The fuel filter was new when I did the check.

I'm hoping its the relay.

Thanks again.
Posted by: DKH

Re: 04 LX - Fuel Pressure Test - 07/20/21 06:28 PM

Originally Posted By RF_Overlord
KOER FP should be 40 lbs, not 30. I've not measured it KOEO. Only time I've ever seen mine read differently was when I drove to the supermarket and the car sat in the hot sun for a while. When I came out and started it, FP was 51 lbs and as I drove home (about 4 miles) the pressure slowly dropped back to 40. I assumed this was the fuel strategy to prevent vapour lock.


Good to know. Thanks.