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.[/align]

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....

my usual recommendation for topics I don't know about is to use a 9v battery. how you use it is up to you[8D]

yes and you have to test it
on your tongue before
installing

ORIGINAL: hammeron

yes and you have to test it
on your tongue before
installing


what's with the poetic format of your posts lately? I keep waiting for some wimpy inspirational crap when I see the line breaks [8D]

i'm a poet and
didn't know it :D

Itsthe duty cycleof the pump to control fuel rail pressure.
Its not voltage, Hamm. :eek:
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.

not bad db, but let's see what the
service manual has to say about it



ORIGINAL: 157db

Itsthe duty cycleof the pump to control fuel rail pressure.
Its not voltage. :eek:
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. ;)



local://upfiles/37808/977097EB0C734E2FB9AEB41AA6DB75D9.jpg

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.

well if you do test it, be careful
and take all necessary precautions

NO SPARKS! LOL

[sm=icon_ladiesman.gif]


:D

ORIGINAL: ebr

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?

ORIGINAL: hammeron

not bad db, but let's see what the
service manual has to say about it

ORIGINAL: 157db

Itsthe duty cycleof the pump to control fuel rail pressure.
Its not voltage. :eek:
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. ;)



local://upfiles/37808/977097EB0C734E2FB9AEB41AA6DB75D9.jpg


Quote, "The FPDMmodulatesthe 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. :eek:

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 leaktest pressures. But then
who has a PWM motor control at their fingertips also. [:o]
Of course, I have both in my junk bin but they are not
for loan. ;)

that did make me laugh.....and no i'm not calling
you wrong at all....

aren't we both saying the same thing tho really....isn't
PWM just another form of a varying dc value

maybe my theory was off.....i will gladly stand
corrected if it is

it just seems like you could use a DC power supply,
to run a pump.....


where's jared when you need him :)



ORIGINAL: 157db

Not bad Hamm, but no cigar on this one. :eek:

ok, db was kind enough to explain
the way it works in more detail and
i think he's got it nailed.

for the record, db does get the cigar
and i learned something new

Yes it would just leak in the tank but I would stand to loose psi as well. Wouldnt I ?

ORIGINAL: ebr

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.:D

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?

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.