Hi guys and girls,

I'm troubleshooting a rough idle at the moment and decided to check fuel preassure. I got a gauge and hooked it up to the Schrader valve on the fuel rail.

These are the Psi I am getting.

Key on warm 55psi

Idle warm 42 psi

Revving in neutral 36 psi
It goes up initially under throttle then falls off to 36 psi at higher revs

I have a jan tune and 450 injectors, RMW cam, RMW headers and 17% pulley.

My spark plugs were showing lean.

Do you have to do this test under load??

I have just been throwing Money at this car trying to sort it and I'm almost out of options.

To make matters worse I recently started getting a ticking from the top left of the engine near the cam sprocket. Already changed the tensioner.

Cheers!!

 

Here is a video which may help

https://youtu.be/HuEaZxrVJQE

Do bigger injectors do that!? Thought it was meant to stay constant

 

I can't remember the actual numbers, but yes you have to check this under load, our cars use vacuum fuel regulators that are controlled by loss of vacuum and this will cause the FP to fluctuate with demand at the rail, where you're reading from. The pressure from the pump itself is still constant.

 

Fuel pressure/flow dropping under load is also a symptom of a plugged up fuel filter. Consider changing it out if you haven't done so already.