[Formulajones]

Originally Posted by gtobird

I'd like to pressure test a new mechanical fuel pump as I keep reading stories about how they are often over or under the PSI specs. This is a standard Carter fuel pump for a vanilla 68 350 carbureted engine with the single input fuel line.

Any suggestions of how to test it off or on the car? I don't want to permanently change the fuel line between the pump and carb by adding a pressure gauge. I've heard of people doing a quick test by connecting the output line of the pump directly to a pressure gauge and just cranking over the engine. Does that provide enough rpm to give a good reading? Open for thoughts or other methods.

Thanks
OJ

You shouldn't really have to permanently change the fuel line to run a test gauge on the car. On cars with factory lines I simply unhook the metal line at the carb. They usually have some wiggle room to pull it away from the carb or to the side a bit. Slide the nut back and push some rubber hose over the flare and install a clamp. I install a short piece of flare steel line to the carb and install another rubber hose and clamp. Between the rubber hose I install a "T" fitting and run a rubber line up to the windshield with a fuel pressure gauge and tape it down to the windshield.

I do it this way temporarily so I can go for a drive and watch fuel pressure for cars that owners complain of laying over. I've been doing this for decades and it quickly helps to nail down fuel delivery issues. When done I remove it all and the factory metal line is reinstalled back on the carb.

It takes a little time rigging but it's what you have to do on some of these cars when you don't want to modify things.

Q jets are a little different in what they tolerate depending on the float design so you really need to know what your pump is putting out. Best way to do that with a mechanical pump is on the car running with the setup I described above. You can bench test the carb with an electric pump if you wish to find it's limit that way but it won't answer your mechanical pump questions.