Fuel pump questions

[Deleted User]

It seems as if I'm having a problem with the double-action fuel pump on my '50 Pacemaker motor, and thought maybe the group had some suggestions:

1) Reinstalling it --- awkward! Has anyone thought of using studs (5/16 x 18, I think they are) made of long bolts with their heads removed and a screwdriver slot cut, like ones often used when replacing heads? Once the pump is positioned, the stud could be left in place and a washer and nut used to secure the pump. (It seems pretty tricky to get the cam positioned so that, even though the arm is below it, the bolts go in easily.)

2) Testing --- is there a way to test the pump before installing it? Activating the arm against its strong springs is pretty tough to do by hand, and I'm not sure if it's a good test anyway. I'm not optimistic about this one. Trying to picture mounting it to some heavy strong fixture, then devising some way to push on the arm...

3) After not starting the motor for a couple of weeks (working on other aspects of the car), it would not start, and I noticed no fuel was coming up from the pump into the glass carb bowl. Removing the bottom cup on the pump to check the screen, I found it bone dry. It should have been full of gas, shouldn't it?

4) Although the pump was not drawing gas in, a pressure gauge on the output showed peaks of about 2 psi just spinning it with the starter. Sound OK? I know that's less than the manual, but its spec is at 1800 rpm.

5) Finally... the diaphragm looks OK, as if I rebuilt it relatively recently (like maybe a few years ago). What else could cause it not to draw fuel, even with a short hose to a can sitting directly underneath it? Valves?

I'd welcome any advice on things I haven't thought of. Everybody has experience with these things!

lostmind

Sometimes the valves stick from dried up gas. The carbs leak down after extended no start periods,

with a stuck valve in the pump and no gas in the carb , you have a no start condition.

Most guys install an electric pump for use as start assist.

Park_W

Werdigo, your pump test is encouraging (2 psi spurts when cranking).  You can make a pretty good test with it in your hand, on the bench or clamped in a solid  vise (but be careful not to put stress on the bolt-hole tabs)..  While holding it in your hand, put a finger in the inlet port of the pump and give it a couple of pumps.  You should feel a little suction on your finger.  Wait two or three seconds, then release from the inlet port. You should feel and hear a little whoosh when the vacuum releases.  You can do the same on the outlet port, feeling for pressure.

I use a common vacuum-pressure gauge to test these pumps.  Connect to either inlet or outlet of the pump, give it two or three pumps and see what happens.  On the inlet side, you should measure several inches of vacuum; on the outlet side two or three psi pressure.  These readings will slowly decrease as you watch the gauge, but it should by slowly.  If the vacuum or pressure drops off immediately, you've got a problem in the pump valves.

Frankvintagefullflowcom

For best cam eccentric positioning, rotate the crank clockwise (as viewed from the front) until #3 is at TDC firing (Just remove the cap and look at rotor position). This puts the eccentric in the uppermost position so you don't have to fight the spring loaded arm......as much.
I has always bothered me that you can't tell if the arm/eccentric contact is at the optimum, i.e., parallel position but there's really no way to "feel" it in there. I've seen many arms and it's apparent that no one else cares. Oh, well.
F

[Deleted User]

Thanks, Lost, Park, and Frank. Here's a progress report:

After opening up the fuel part of the dual-action pump and seeing nothing obviously amiss, I reassembled it with newly cut cork gaskets around the lip of the cup and the center bolt that secures it. I then filled it with gasoline (slowly pouring it in the inlet until it began to dribble out the outlet) and (with some, but not as much as sometimes, difficulty) remounted the pump on the motor.

To make spinning easier I removed the spark plugs. When the system was open, some fuel had evaporated from the glass carb bowl so it was only about half full. Using a remote starter switch I spun the motor and soon saw gasoline start to drip down into the glass bowl --- then surge in with each revolution. When the bowl was full, I replaced the plugs, turned on the ignition... and the motor fired and ran immediately.

I let it idle for about half an hour to make sure it was pulling gas from the fuel tank; the in-line glass filter looked clean and full. This morning (two days after all of the above) it started easily and I drove the car a few miles.

Wish I knew for sure why that happened, though. Maybe the dried-out cork gaskets on the bottom fuel-pump bowl allowed the fuel in that bowl to evaporate (remember, when I first opened it, it was bone dry). Maybe that would let the valves dry out (Lost's suggestion). I have a couple of 6v electric pumps but have resisted using them. If this happens again maybe it'll be time.

Thanks again for the advice, guys!