Does anyone know how to test the fuel pumps for psi and volume with the motor out of the car? I would like to test the new setup (dual gt40 pumps dual -6 outlets and -8 line to the firewall) now before the motor goes in and the car goes to be tunned.
i noticed you're not getting very helpful answers on the other 2 forums where this was also asked, so i thought i'd give it a shot.
since i don't think you can easily simulate a duty cycle command from the pcm to the FPDM(s), you might have to use a variable DC power supply, to control the pumps directly.
you would open the control voltage line between the FPDM(s) and the pump hat and control the pumps there (for your flow tests).
i would feel confidant doing such a procedure, but if you don't, then it's not something you should try
there's also the possibility, that i'm way off base here and that there is another much simpler and smarter way to do it....
Its the duty cycle of the pump to control fuel rail pressure. Its not voltage, Hamm. 12V constant is a 100% duty cycle so hooking it to 12V constant would simulate a 100% flow rate or what the pump is capable at 100% duty cycle. We (S197s) use a returnless fuel system and the FuelPumpControlModule gives the pump 12V but with a specific duty cycle according to fuel rail pressure. I have no idea what the 9V battery is all about. It does not have enough amperage to drive a pump.
< Message edited by 157db -- 5/12/2008 8:41:33 AM >
not bad db, but let's see what the service manual has to say about it
quote:
ORIGINAL: 157db
Its the duty cycle of the pump to control fuel rail pressure. Its not voltage. 12V constant is a 100% duty cycle so hooking it to 12V constant would simulate a 100% flow rate or what the pump is capable at 100% duty cycle. We (S197s) use a returnless fuel system and the FuelPumpControlModule gives the pump 12V but with a specific duty cycle according to fuel rail pressure.
So to ck for leaks at the pump at least would I be able to connect 12v to the pumps with the line closed an watch th fuel psi gauge so not to make to much psi and with that being said what would the max psi be that you guys would go to just to test for leaks? And yes Hammeron I am not getting very many replies on this maybe its becouse it cannot be done correctly IDK but I do thank you guys for the help.
well the reason i suggest a variable DC power supply, is so you can bring the pump control voltage up slowly and methodically.
if you're just testing for leaks to say the engine bay, then you could bring the voltage up, until your pressure gauge reached your desired test level ie 30 - 50 psi
Short of doing flow tests ect. I would at least like to ck the pump for leaks under presure becouse I built it my self.
If it leaks, wont it just leak into the fuel tank?
quote:
ORIGINAL: hammeron
not bad db, but let's see what the service manual has to say about it
quote:
ORIGINAL: 157db
Its the duty cycle of the pump to control fuel rail pressure. Its not voltage. 12V constant is a 100% duty cycle so hooking it to 12V constant would simulate a 100% flow rate or what the pump is capable at 100% duty cycle. We (S197s) use a returnless fuel system and the FuelPumpControlModule gives the pump 12V but with a specific duty cycle according to fuel rail pressure.
Thumbnail Image
Quote, "The FPDM modulates the voltage to the Fuel Pump." Quote, "The PCM commands a duty cycle to the Fuel Pump Driver Module."
I dont get it, are you calling me out as being wrong, Hamm? Its not the voltage but the PWM or PulseWidthModulation that controls pump pressure. I verified this with a scope before posting this. Not bad Hamm, but no cigar on this one.
quote:
ORIGINAL: hammeron
well the reason i suggest a variable DC power supply, is so you can bring the pump control voltage up slowly and methodically.
I would suggest using a PWM motor speed control. The voltage needed to start the pump pumping will be nearly 8V or so and just who has a variable power supply capable of the amperage needed to run the fuel pump at leak test pressures. But then who has a PWM motor control at their fingertips also. Of course, I have both in my junk bin but they are not for loan.
< Message edited by 157db -- 5/12/2008 8:55:55 AM >
Yes it would just leak in the tank but I would stand to loose psi as well. Wouldnt I ?
Yes you would loose psi or rather you'd only be able to reach a certain psi. My pressure does start to drop slowly after the pumps prime for 3 seconds. I'm not sure if you were planning to run them for a few seconds and then see if the pressure holds. I'm pretty sure that it's normal for the pressure to slowly leak back through the pump, otherwise why would the pumps need to run for 3 seconds every time you start the car.
Now the question is how will you know if you have a leak? A big leak will be obvious, but what about a small leak? I've seen my fuel pressure reach 76psi at WOT and i've never seen the duty cycle go over 50%. If you can maintain 70psi, then you're probably good for no leaks.
Off topic, but if you have 60lb injectors, what would your fuel pressure be at idle/cruise? Is it always the same regardless of the injectors?
_____________________________
whipple HO SC,FRPP springs, Pypes mid mufflers, Che adj. LCA, hurst, 4.10's, 1 piece DS, spec stg 2 clutch. Accel coils 12.52@117.6mph so far with a 2.01 60 ft time(pre shaft, coils, clutch).
I think I will just wait till I tune the car and see what it does on the dyno . Im going to tune more localy now at HPP instaed of the long drive to JPC so it is not as big of a concern now I guess . And Moose I did not have the fuel pres. gauge in the car with the old setup so I do not know about the fuel psi with different injectors but someone else will probably chime in on this one.
Printable Version
Testing fuel pumps - 
