how to test fuel pump delivery ?

[prebordao]

what's the right procedure for testing the delivery specs of the fp ? do i need to keep cranking the starter to keep the pump running ?

[ossiblue]

Originally Posted by prebordao

what's the right procedure for testing the delivery specs of the fp ? do i need to keep cranking the starter to keep the pump running ?

Couple of threads have been posted about testing--basically, pull the injectors, place them in glass containers and measure the volume over a period of time (specifics such as time and volume of fuel I don't have committed to memory but you can easily find.)

To answer your "cranking" question, no, you don't crank the car over. Simply turn the ignition to the "on" position, remove the air cleaner, and gently push up on the plate inside the intake--that will activate the injectors. Your car is a 74 so the fuel pump will start with the ignition on (and will continue to run while it's on) but you need to lift the plate to feed the injectors.

Check out this thread: Checking Fuel injectors

[prebordao]

So I guess that if I want to just test the pump I can drop the fule line into a jar and just turn on the ignition, no need to lift the plate.

[ossiblue]

Originally Posted by prebordao

So I guess that if I want to just test the pump I can drop the fule line into a jar and just turn on the ignition, no need to lift the plate.

Yes, that will give you the volume delivery of the pump alone. However, in that circumstance the pump will not be under the same back pressure as it would in the "real world" of pushing fuel through the injection system. Measuring volume of delivery through the injectors will tell you if the fuel flow against the resistance of the complete system is adequate.

[prebordao]

I had a look at the procedure described in the workshop manual for measuring fuel delivery at the pump, and they say it must be measured at the return line to the tank and not at the pump exit.
I guess this way is a more realistic setup as fuel is able to travel through the whole circuit.

[boyt911sc]

Originally Posted by prebordao

what's the right procedure for testing the delivery specs of the fp ? do i need to keep cranking the starter to keep the pump running ?

prebordao,

To determine the FP delivery (capacity), measure the pressure or volume delivered per unit time. In short, the FP should be running to do the test. A very simple way to do it in your '74 car is do the measurement right after the FP outlet. Since it is not convenient sometimes, you could relocate the testing location. For example do it at: (1). Before the fuel accumulator, or at (2). After the fuel filter, or at (3). Return line to the tank. At equilibrium or steady state, the mass of material transferred or delivered at these points should be the same.

BTW, checking the amount of fuel coming out of the injectors does not tell you the FP capacity!!!!! The amount of fuel collected thru the injectors depends on the plunger's position. In your case, all you have to do is turn the ignition switch and have the FP run. Then do the measurements. Keep us posted.

Tony

[prebordao]

Just measured the output at the return line to the tank and it was 1L in 30 sec, so I guess it's ok.
The manual states at least 0.85l in 30s