Technical Float height and fuel pump pressure

Truck64 - the pump pictured above is a Carter pump. Airtex may have reboxed it. The Carter number is stamped on the edge of the mounting flange.

Jon.

 

Yes, I tested my pump and it measured 5 psi while the vehicle was running. I have a SUN inline fuel pressure tester (came with my Sun Machine).

Several years ago when I began the search for a fuel pump I contacted both Airtex and Carter and spoke with their technical departments. Carter had the only pump that would work for my application. The Airtex equivalent psi max was much higher if I remember correctly.

Finally, the M3528 Carter pump looks very different from the pump you have pictured.

 

Ah, OK good deal, good to know at least one manufacturer still pays attention to this stuff.

Well it should, that's the NOS replacement, the airtex brand pump is installed now. Sorry for any confusion. The Airtex and Carter pumps sold as suitable for the Y Block and FE look very, very similar, with the integral fuel filter metal canister &c.

 

Just a side note, you car run the autolite carburetor with the top off, then you can monitor your float level.

 

No thanks, not with the POS fuel pumps they are selling!

 

NOS pump output at the carburetor 5.5 psi, go figure!

 

Looks to me after some checking no adjustment of the float required?

This surprised me, before firing it up and leak checks, I first thought about adjusting it to the dry float height and then thought no, let's just see what it does with the new pump.

Fuel height in the bowl at idle looks perfect. The big difference though, it doesn't look like Old Faithful anymore gushing past the needle and seat at idle. More volume, less pressure, how does it work, I dunno but it sure seems safer to me. I used to see a little bit of fuel on top of the booster cluster screw area after a highway run, thought maybe it was leaking past the cluster gasket. I bet needle and seat was spraying far and wide is what it was.

The shop manual explains some of the fuel pump testing @saltflats was talking about. In that test they have an extra hose plumbed to a bottle to test for both volume and pressure at the same time. I sort of understand what you were getting at now.

Cruising down the highway and I get to p***ing someone say, the pressure could practically go to zero if the engine used all the fuel coming in at that point. So long as the volume is sufficient no problem, but, the pressure (and volume in the bowl) has to stay within spec at all times under all conditions, even when at max fuel demand.

 

good to see you are up and running.nice to see you update everyone

 

On GP replaced the needle and seat, the overpressure caused a pretty deep gouge in the viton tip in a short period of time. Didn't trust it. It did good under abuse and never flooded out, but. Reset the float height to stock spec and it seems a whole lot happier and fuel height looks good. Consider this matter closed.