1928 chevy vacuum fuel pump issues

[Guest ottodoc]

rebuilt a vac. fuel pump on a 28 chevy and its drawing raw fuel into the vacuum line.

any thoughts on how to correct this condition?

while tank is in "fill mode", car runs rough and will load up and stall if not taken to a high idle

once tank is full and float toggles off the vac. port car smooths out till next fill cycle.

tank does have .040 orifice in vac port.

also has small tube where wiper vac. is attached.

putting a small clear hose on this port attached to vac. gage, one can watch raw fuel weep into hose

during fill cycle.

[oldford]

Sounds like the float is not adjusted correctly. Maybe rises too high before shutting off the valve, or the valve is not closing...

Frank

[sambarn]

If gas enters the vacuum line, the valve is leaking. Either alignment or needle valve. The .040 retrictor. Shouldn't that be on the fuel fill side?

[rsb]

It sounds to me like one of the following possibilities:

1. The float cracked, filled with fuel, and sank (most common)

2. The float is not installed properly on the hook

3. The float valve is sticking or leaking. Trash in valve.

Regards,

Ron

[GLong]

Sometimes the springs that the 'teeter-totter' levers are held in place with are too stiff. Take the top off the tank, and confirm the float is not full of gasoline. If it is not, then lift the float on it's guide, watching the levers and valves at the top. Sometimes the float can be pushed quite a bit higher than it should before the levers [the teeter-totter] will go over center and close the vacuum valve and open the vent valve. If the springs are new, stretch the spring a bit to weaken it.

In the rebuild kits from one of the Stewart Warner tank guys, his directions state that the springs may need a slight stretching to weaken them.

Hope this helps.

GLong

[Guest ottodoc]

thank u on the replies I will try stretching the springs slightly. the float is new and I lapped the 2 brass valves as good as possible

if I hold either valve closed I cannot blow air thru them so I believe that is ok I checked the flapper valve and it holds as well.

If I am understanding about the springs, if they are to strong it allows the tank to fill too much before the valves toggle off,correct?

[rsb]

I suppose you could always drain and remove the tank, then slowly fill it with a funnel through the fuel inlet. You could then observe when/if the float closes the vacuum valve. They used two types of Stewart tanks on the 28 chevy. One had the springs and 'teeter-totter' action as mentioned and you should hear it click when the valve closes. I assume that's the one you have.

http://books.google.com/books?id=BtYbqYNbg0QC&dq=dyke's%20automobile%20vacuum%20tank&pg=PA165#v=onepage&q&f=false

Regards,

Ron

Edited April 28, 2014 by rsb (see edit history)

[hddennis]

Howard Dennis

[Guest ottodoc]

to howard, that's a great little booklet on the pumps. unfortunately I cannot blow it up far enough to read it. it may just have some good tips on this trouble im having. could you advise me on how to get a copy?

to rsb, yes I do have the teeter-totter type pump. gonna give the spring stretch a try. it may be the answer to the trouble im having

if the tank fills too full before switching off.

[GLong]

Before stretching the springs. [since it's so darned difficult to 'un-stretch' them] I'd lift the float up and down several times and watch the action of the springs. levers, valves etc. It's a fine balance of lever movement vs spring tension, with a dash of friction thrown in for fun.

Once you opperate the float up and down a few times, you will find the spring that is just a bit too stiff. I found this by holding the float up. Then used a small screwdriver or pick to gently 'help' the appropriate lever to 'trip' and close the suction/vacuum valve and open the atmosphere valve.

Just operate it several times, you will be able to see what needs adjustment.

GLong