Fuel System: Testing Fuel Pump

[valleyguy]

Appears the fuel pump may be bad; 1961 Lark 259 engine; only pumps gas in little spurts; I removed the pump and when activating (working the lever) by hand, it is pushing air, and I can
hear the diaphram working. Wonder what is going on? would like to know before I spring for a new pump.


Thanks,

Joe D.

[JoeHall]

Appears the fuel pump may be bad; 1961 Lark 259 engine; only pumps gas in little spurts; I removed the pump and when activating (working the lever) by hand, it is pushing air, and I can
hear the diaphram working. Wonder what is going on? would like to know before I spring for a new pump.


Thanks,

Joe D.

Not trying to be a butt-head, but the only test I would give it would be to see how far I could throw it. Then I'd put a block-off plate over the original mount hole, and install an electric pump on it. But that's just me.

[valleyguy]

No offense taken; I hear what you're saying; thats the way (electric) most folks are going and I would too if:
the car has problems with vapor lock (it doesn't); if it was a daily driver (its not); if I was worried about
dependability for long trips (not an issue). Just trying to assess the current problem. Any help appreciated!


Joe D.

[RadioRoy]

The shop manuals used to have a test where you would disconnect the output line of the pump and see how much it pumped into a glass jar per minute with the engine running on the gas still in the carb.

Did the car recently stop running? What steered you towards the fuel pump initially?

[StudeRich]

I have always wanted to try testing a fuel pump the right way. Most of us have a Vacuum gauge, all you need is to rig it up to the fuel Pump output and find out what your PSI is. I guess the Gallons per Minute test would be a little trickier but also doable.

[jclary]

Well...continuing the theme of not trying to be a smart a**...all mechanical diaphragm fuel pumps, pump in little spurts. Each stroke of the actuator arm results in one spurt. The key in our older carburetor aspirated engines is that it pumps enough to supply the reservoir with a steady and sufficient amount of fuel to meet the engine demands. If it pumps, but not enough, the most likely culprit is the diaphragm has a leak (hole) or the little check valves are failing. Usually, a leaking diaphragm will be blowing a mixture of gasoline and oil out the vent on the back side of the diaphragm.

Some of our gas tanks have a small fine screen wire like pre-filter on the pick-up tube. If that gets clogged with trash, it can make you think the fuel pump is the culprit. Although these old systems are relatively simple...making the wrong assumption and concluding the wrong problem will drive you nuts.

[valleyguy]

Good point John on the pick-up tube; how does one get to that? (please don't tell me I have to drop the tank)

This is a 1961 Hawk with a 259 ci V8 that belong to an friend..

The complete story is: the car has not been started or run for a year or so, and in fact run very seldom over
the past 3 years. The last maintenance record (2010) show new points, condensor and resistor. Supposedly,
it had been well maintained by the po, who was a mechanic.

I added some gas and gas stablizer to the tank. Cranking the motor, initally, there was no spark.
So I ran a point file between the points and got a good spark. Then, I primed the carb with gas and it started,
but running very roughly, and died in a few seconds. Did this several times. So I figured it wasn't getting
sufficient gas. I disconnected the line before the carb, put the end in a large jar, and cranked.
Some gas, in spurts. as I mentioned. To check further I put an in-line clear in-line filter in and cranked again
several more times. Still very little gas entered the filter, car would still run no more than a few seconds.
I didn't see any gunk in the filter.

So thats where we are right now. No doubt the carb is gummed up I need to get the fuel delivery thing figured
out first. It has new plugs and is getting spark.

Should I start back at the tank and work forward? Any thoughts appreciated.

Thanks,

Joe D.

[jclary]

You can disconnect the fuel line at the inlet of the fuel pump and see if you have good fuel flow by gravity into a jar. If you have a good amount of fuel in the tank, I believe it will be low enough at the frame rail to free flow into a container. That should give you a good idea if the line is clear to the pump.

[jclary]

Another alternative you can do, depending on your level of tinkering skills, is to cap off the fuel pump and rig up a small gravity feed tank to feed the carburetor. I use an old lawn tractor tank with an inexpensive shut-off valve. As always, please be careful and safe when playing around with gas and gas fumes. Good ventilation and avoid any source of spark...keep a fire extinguisher handy.

[RadioRoy]

You can also blow compressed air back towards the tank from the line you disconnected from the INPUT of the fuel pump.

I am still not convinced that the fuel pump test is showing a bad pump. Too bad there is no quantitative data.

Performing the external fuel can test will eliminate the entire pump and fuel line system and is a good starting point.


As additional information, the mechanical fuel pump pumps a lot (like a LOT in big letters) more fuel with a running engine than with a cranking engine.

Good luck and please keep everyone posted.

[altair]

fuel pump

Good point John on the pick-up tube; how does one get to that? (please don't tell me I have to drop the tank)

This is a 1961 Hawk with a 259 ci V8 that belong to an friend..

The complete story is: the car has not been started or run for a year or so, and in fact run very seldom over
the past 3 years. The last maintenance record (2010) show new points, condensor and resistor. Supposedly,
it had been well maintained by the po, who was a mechanic.

I added some gas and gas stablizer to the tank. Cranking the motor, initally, there was no spark.
So I ran a point file between the points and got a good spark. Then, I primed the carb with gas and it started,
but running very roughly, and died in a few seconds. Did this several times. So I figured it wasn't getting
sufficient gas. I disconnected the line before the carb, put the end in a large jar, and cranked.
Some gas, in spurts. as I mentioned. To check further I put an in-line clear in-line filter in and cranked again
several more times. Still very little gas entered the filter, car would still run no more than a few seconds.
I didn't see any gunk in the filter.

So thats where we are right now. No doubt the carb is gummed up I need to get the fuel delivery thing figured
out first. It has new plugs and is getting spark.

Should I start back at the tank and work forward? Any thoughts appreciated.

Thanks,

Joe D.

If you have the fuel pump off fabricate a fitting on the suction inlet and attach a small short hose and put it in a jar of solvent then actuate the lever by hand, if it is in good shape it will pump the liquid in 3 or 4 pumps and should discharge across the room at least 6 feet if the discharge is limpy the diaphgram is shot. Dave

[christophe]

If your car is equipped with the spongy filter in the glass bowl, you should run a test without it. In my case, it was responsible for the too low pressure. Test with a pressure gauge, you should be around 4-5 PSI (check the value in manual to be sure) with the engine running.
Best of luck.

[valleyguy]

ok guys, an update: I tried Dave's suggestion and the pump DOES squirt solvent 6 feet or so out, so it looks like the pump
is ok. I also blew compressed air back through the line to the tank. (btw, the pump does not have the glass bowl, just
the above mentioned in-line filter). After I the shot the air through the line, I left to wrap my compressor hose back up;
when I got back to the car, there was a large pool of gas on the garage floor under the engine. That didn't happen yesterday when the line was disconnected. Looks like the fuel line from the tank really gave up some gas... (I checked for other leak sources. didn 't see any).


Now, in trying reinstall the fuel pump, I have a problem. My understanding that the actuator level should go under
the cam lobe, but when I try to push it in that way, its a no go. Any trick to get the pump back in place in the correct position.?? If I can get it in right, I'll try cranking again and see what happens. ......

Thanks,

Joe D.

[41 Frank]

Your fuel line was probably partially plugged. Try turning the engine over a little bit to get the fuel pump lobe on the lowest spot, that will make it easier to get the pump arm back in.

[jclary]

One thing that Studebaker was ahead of its time...a tidy and tight engine bay. I have owned other makes of the era that I could just about stand on the ground and work on the engine under the hood. Not my Studebakers.

I have always found installing fuel pumps somewhat awkward on a fully assembled car. The actuator arm is capable of a much larger stroke than it really needs from the cam lobe. Unless you are very lucky and the engine is positioned perfectly (rarely the case), you have to get that first bolt started while holding the fuel pump in place against spring pressure. A challenge for sure, but I have done it many times. If I can do it...anybody can.