how do you do fuel pressure test

[663CSX-T]

how do you do the fuel pressure test dose fule pressure need to be at 55 when car is runnig or when key is turn on im not sure what the right way to do it can some one tell me step by step how to do test need help thanks every one (804 injeters)

[85daytona]

I personally haven't done this yet but I'm sure it will help you out

Diagnosing Your Fuel System - MiniMopar Resources

[NAJ]

Connect fuel pressure gauge to service valve on fuel rail.
Static Rail Pressure(key on/engine off) on a MPFI is 53-57 PSI.There are 2 ways to test.
1) Turn the key on then off,wait a few seconds turn the key on then off, you may have to do this a couple of times until all air is purged and the rail and gauge are at max regulated pressure.
2) Locate the underhood diagnaostic connector(in the harness by the controller) and with the key on/engine off ground the DB/YL wire, this actuates the ASD relay and the pump will run, read pressure.(Do Not start the vehicle with the wire grounded)
Checking running rail pressure
Start the vehicle and read pressure, rail pressure will drop 1 PSI for every 2" vacuum applied to the Fuel Pressure Regulator.
(MPFI works on Pressure Differential across the Injector, but that is for another day)
Ex. Static Pressure = 55 PSI, Vehicle running rail pressure drops to 46 PSI with 18" Vac at the FPR = 55PSI.
Check Pressure at 2000 RPM's.
This is easier if you tee a vacuum gauge inline with the fuel pressure regulator so you can read pressure and vacuum at the same time.
All Readings should be equal to static rail pressure.
With the engine running if you remove the vacuum from the FPR rail pressure will increase to static rail pressure(this is max regulated pressure)
If you are going to check while driving fuel pressure will increase 1 PSI for 1lb of boost.
When the engine is shut off pressure should hold, if it drops suddenly there is a leak in the system.(pump, fpr, hose, injector(s) etc.

[663CSX-T]

Thanks For Your Help

[NAJ]

Not a problem, that is what we do.
Any other problems/questions feel free to post.

[663CSX-T]

fuel pressure is at 40 when running that means i should just turn the pressure up right (if fuel pressure is not set right as in set to low wood it smoke what would happen

[NAJ]

From what you are saying I assume you are running an AFPR, is this correct?
If so what other mods are you running?
What was "static" rail pressure?
Low fuel pressure will create a lean condition.
What type of smoke/problems are you having?

[663CSX-T]

yes i have a (afpr)static pressure is @like38 wallbro fuel pump molly 20 over pistons all new head parts every thing is new or re done (20 miles on morter) the smokeing thing oil and coolet in ceery boom from befor

[NAJ]

I do not know what fuel pressure should be with your mods, someone will know, they will probably tell you you need an A/F gauge.
Black smoke is rich
Gray is oil
White is coolant