LPFP pressure when running

Does anybody monitor LPFP pressure when driving? The Ford specification in the Hard Start/No Start Guide is 3-8psi. I was watching mine today and when the truck was cold it would drop down to .5psi. The longer I drove, the better it got. By the time I was at the end of my hour drive, it was between 5.5 and 7.3psi (digital gauge).

Any input on this?

what are you using to monitor?

Electronic Waekon gauge hooked up via transducer to the port on the fuel cooler.

I'm pretty sure that the fuel cooler is on the return side, maybe it would be different on the pressure side of the hpfp

11. Electric Fuel Pump Pressure Test
Note: The fuel pump runs for approximately 30 seconds at initial ignition on and then the
pressure decreases.
Purpose:
The purpose of this test is to verify there is sufficient fuel pressure for starting.
Electric Fuel Pump Pressure Test
• Verify there is fuel in the tank.
• Check the fuel pump power and ground circuits.
• Measure the fuel pressure using the Fuel Line Adapter 310-159 or equivalent.
Note: If using a scan tool for the fuel pump pressure test, the scan tool value may vary by 10% on the 20.7 kPa (3 psi) specification.

Instrument Specification Measurement
0-200 kPa (0-30 20.7-55.2 kPa
psi) gauge (3-8 psi)

Measuring the return side is correct

I am by no means an expert, but the readings that everyone is giving for maintaining fuel pressure is on the return side? I deleted my fuel bowl and just t-ed in on the feed line coming off the airdog feeding the hpfp

superdutyfarmer said:

I am by no means an expert, but the readings that everyone is giving for maintaining fuel pressure is on the return side? I deleted my fuel bowl and just t-ed in on the feed line coming off the airdog feeding the hpfp

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If you deleted the fuel bowl or are running a non regulated return fuel psi must be checked on the supply side

Thats what I thought. Not trying to hi-jack your thread but one more quick question, what is too much fp to the hpfp, I was told 11 and also 15, I realize it may be different since I am not measuring the same way

superdutyfarmer said:

Thats what I thought. Not trying to hi-jack your thread but one more quick question, what is too much fp to the hpfp, I was told 11 and also 15, I realize it may be different since I am not measuring the same way

Click to expand...

Anything under 20 seams to be ok. Not sure at what point could cause the pump to leak or get damage

Ok, so time for a LPFP. Good thing I just happen to have one on my desk as I type this!

3 PSI on the return is normal, you should see around 7 on the supply side with the stock pump. For the guys deleting the fuel bowls and running an aftermarket lift pump to the HPFP I wouldn't do any more than 10 psi to it. I forgot where I read it but I think it was the Ford tech manual and it stated not to exceed 10 psi on the supply side of the HPFP.

LPFP installed and the lowest the pressure drops on the return is 3.0psi. Normally it is 3.5-5.2psi. No more P0232.