How do I test mechanical fuel pump

[Turbo4whl]

It has a fuel return on it

The third port is not a fuel return, just a vent. Older pumps just vented to atmosphere. EPA wanted them vented to the tank.

Fuel injected needs a return, carburetors do not.

 

[Matt69olds]

The 3rd hose fitting is a return. It’s designed with a tiny orifice to provide a controlled leak back to the tank. Its purpose is to constant circulate fuel to keep the pump cool, and to vent excessive pressure back to the tank after shutting off the engine in hot weather.

 

[75gmck25]

My ‘75 350 has a three port fuel pump with a return to the tanks. I have replaced the fuel pump twice (one leaked) over the years, and found the Autozone pumps worked fine. Some Autozone stores do not stock the correct 3 line pump, so I had to get it from one of their bigger regional stores.

At one point I also used a brass block to install a fuel pressure gauge in the line at the carburetor, and verified I was getting correct pressure at all rpm. I had the gauge duct-taped to the windshield so I could see it and drive the truck. They sell the fuel line blocks with a gauge fitting at most parts store.

 

[Broken85]

Now that is a write-up!

It is faster to just put a new fuel pump on than read this whole thing!!

 

[Ricko1966]

It is faster to just put a new fuel pump on than read this whole thing!!

Except 1/2 the new pumps are bad right out of the box. So you change the pump, things still aren't right so it must be something else,so you replace 1/2 a dozen more things before you test the new pump and find out it's bad. No joke peruse the forum see how many people got bad new pumps or pumps that failed almost immediately.

 

[Grit dog]

Everybody pump the brakes. I missed it too, but we’re answering questions from a post a year ago who never came back because someone had a slightly related question and resurrected the old thread.

 

[Ricko1966]

Everybody pump the brakes. I missed it too, but we’re answering questions from a post a year ago who never came back because someone had a slightly related question and resurrected the old thread.

Yep I was just noticing that myself. I say we hang him.

 

[idahovette]

I think it's called "reading and comprehending"??

 

[fnny6770]

I'm an innocent victim!