[MPKind]

The pump is a Carter M6907. Street Super pump. Like everything on my car its shelf life got to it before it failed on its own. Between the bad coil and a weak pump it’s been a real challenge to keep this car running.

So I tested the pump and it went as high as 5.5 psi at 1000 rpm and faster. Tried it at cranking rpm. 4.5 psi. Tested it a 3rd time running again. 4.5 psi. After shut down the line pressure bleeds off to zero in less than 5 minutes. So that’s not good. No fuel in the line means extra cranking when cold. And it’s been a real bear to keep running when cold.

I considered rebuilding it but I doubt there’s a kit for it. For another $125 I guess I can just put a new one in and hope it works as advertised.

[steve25]

From personal experience I can tell you that a warmed up motor with a Q-jet will idle fine at 3.5 psi and allow about 20 mph to take place on level ground, or about 1800 rpm��

Yes you will not likely find I kit for that unfortunately.

[MPKind]

I agree. It’ll idle all day the way it is. It’s a QJet setup on a 455. So it thirsty.


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[Schurkey]

Three tests to be made on an engine-driven fuel pump:
1. Pressure

2. Volume

1 and 2 are done on the fuel pump outlet fitting, or at the carb, or somewhere in between. Fuel pump discharge side.

3. Vacuum. The test everyone forgets about. Fill float bowl, disconnect fuel pump inlet hose. Connect vacuum gauge to inlet of pump. Start engine--engine runs on fuel in float bowl. Vacuum better be significant, and it should hold vacuum for a minute or ten when the engine stalls from lack of fuel.

[MPKind]

I filled the bowl and did the pressure test. It was below specs. Didn’t do a volume test or vacuum test. The pressure dropped in minutes after shut down. So I think that tells the tale. The check valve seal is weak. That’s my best guess.


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[tjs72lemans]

With the posts of crappy fuel pumps out there for sale, I think I'd stick with bleed down and hard starts over a new failed pump on the road.

[steve25]

I think your pump has a small crack in its diaphragm and or the check valve is pitted and leaking.


That would certainly allow the pressure to bleed down once the motor is not running.

That pump is spec’ed for 6 psi and you are only reading 5.5, which further supporting the notion that the pump has a issue.

Also that Carter pump only has 1/4” nPT fittings .
On the suction side that’s not much of a issue, but on the outlet side when you look at how the ass end of a 1/4” pipe gets necked down to make the threaded portion it’s a definitive restriction.

Not that I am saying that’s your issue, but I think that you plane and simple need a new pump so look into one that has inlet and outlet ports bigger then 1/4”
pipe.

[Schurkey]

You're likely going to replace it anyway.

Pull it apart, see if there's some debris stuck in one or more of the check valves. Look at the diaphragm to see what condition it's condition is in.

MAYBE you find a fixable problem. Reassemble, drive away. If not, you're buying a new pump, you're out nothing but your time and effort.