Ok, I’ve been testing various components of my fuel system today and it led me to the thought of how to really test the capacity of a fuel system besides just hooking everything up and seeing if the car holds pressure at peak output.

I'm not worried about injectors in this particular situation, although I know that they are a very important part of the overall equation.

Tell me if you guys think this is a legit test for the fuel pump and supporting lines.....

1.Pull off return line to tank and let it drain into a container until it stops
2.Once fuel stops flowing, stick the line into an empty gas can.
3.Set regulator for desired testing pressure (60psi would be the norm)
4.Command fuel pump on with BAP hard wired on. (this can be done with a scanner…)
5.Run pump for 5 minutes and verify that pressure remains constant.
6.Measure volume of fuel in gas can.


I’m looking for a way to baseline the system….

These fuel pumps seem to be a real crap shoot and I want a way to know if I got what I paid for. I also want to have a way to determine if improvements help… Did putting in a different filter increase capacity...

I have a feeling that this new pump I recently purchased was the runt of the litter

 

I follow what you are trying do. Performing a catch (weight over time) to determine flow is done everywhere, especially when trying calibrate mass flow meters. To be accurate you need at least a minutes worth of flow.

If you can add heat to the equation, then that would be interesting. As the vapor pressure level changes on pump suction, flow should fall off. An important variable would be to have similar pressure drop as on normal system (-6 fuel line, fuel rails, return…).

Oh, fuel pumps have allot of variability, as an example the low and high pressure Bosch 420 pumps are some units except high pressure units are the ones that after testing where able to support high pressure spec (better tolerances).


Mike

PS if you want to do some in-car testing I have some good data acquisition equipment kicking around with numerous sensors.

 

You have described the exact test I used to test my fuel system capacity. You might want to shorten the test time, Hopefully for high horsepower situations you will be pumping in excess of 1 1/2 gallon per minute. It is also a good time to verify that the pressure regulator controls pressure well , with and with out the added boost-a-pump voltage. Just verifies the regulator can handle the extra flow when the boost-a-pump first comes on ,before the fuel is being consumed by the injectors.
While talking about regulators I use an Aeromotive small but high flow regulator. My first one would not hold pressure when the pump was turned off. It would bleed down in a couple of minutes. I bouught a new one it did the same thing. I machined and polished the seat on the second one, it now holds pressure for several hours, far better, but not what I would like to see from a regulator, model #13105. It regulates well over varying returm amounts of fuel, but does not hold pressure when the sytem is off.

 

The results would depend on what kind of fuel system you're testing.
If you have the stock system with the bypass regulator at the back near the tank and the engine isn't running, you would show higher flow than is available to the engine when actually running.
With the test you described on this system, you wouldn't be accounting for the pressure and flow drop in the tubing from the regulator up to the engine. The higher the engine demand, the greater the drop by the time it reaches the rails. You could have 60 at the regulator, but 40 by the time it reaches the engine at full throttle.

If you have a bypass system with the regulator mounted near the rails, your flow would be lower than what is available to the engine, because none is being used by the injectors, and all will see the additional restriction of the return line to the tank before being measured.

Might be more precise to take the fuel from the fuel rail. Put a valve in the line from the fuel rail to the gas can so you can vary flow all the way from idle requirements to full throttle requirements, and monitor pressure between these ranges to see if it stays at an acceptable level.

I'd think you'd also want to run the system for an hour or so with the fuel tank level low to warm things up before doing the test.

 

In my test, the fuel pressure regulator is front mounted, and the fuel pressure gauge should be on the fuel rail and I connected a fuel return line from the regulator to my measuremement bucket (six gallon plastic gas tank). Also if you want a more accurate voltage at the pump to simulate driving voltage, you can put a 20 amp or so charger on your battery , as I did.
Sure things are going to change with temperature and time, but this will give you a good first order answer. It would also be easy to duplicate when changes are made, for relative differences.

 

Yea, I have a return on the rail. I'm mainly looking for relative differences.