The Stovebolt Site Forums The Shop Area Engine Shop Fuel Pump Cam Wiped?

As some of you may remember from another thread, my truck appeared to be suffering from vapor lock. No fuel was reaching the carburetor.

When the line was disconnected at the carb inlet, there was virtually nothing but air present.

The line was then removed at the outlet side of the fuel pump. When the starter was pressed, a trickle of fuel spritzed out but was primarily nothing but air. This led me to believe that the pump had failed and a new Carquest fuel pump was installed. The same results were seen. Zero fuel was making its way out of the fuel pump.

With both pumps it was verified that fuel was indeed present at the intake side of the pump. That's one advantage of the gravity fed tank in the cab.

The first pump was installed in May 2021. It has been working more or less perfectly until the recent trouble. A couple of incidents recently that I attributed to vapor lock or stuck carb float, I now believe were the precursors to the present condition.

As you can see, the Carquest pump has wear on the arm in just a small area when compared to the original glass bowl pump removed a year and a half ago.

I took pictures of the cam in case anybody's interested. I don't know if there's any information to be gleaned from those photos but who knows?

What caused this? Is this "normal" on a 72 year old 216? I've never had anything like it occur on any vehicle I've ever owned and the only vehicles I've ever owned in my life are antiques.

Since it's virtually impossible to install the fuel pump incorrectly, what do you think caused this? Even if the new pump was installed incorrectly, it doesn't explain the sudden failure of the first fuel pump resulting in identical symptoms.

I installed both pumps again today just to see if I achieved different results. Nothing has changed. I may install the original glass bowl pump just to see what happens but that one was done in by ethanol many years ago.

It should be noted that there was fuel present in the first Carquest pump when I removed it from the engine. Working the arm manually resulted in large spurts of fuel so I'm pretty sure the fuel pump isn't defective. And what would be the likelihood that a brand new fuel pump wouldn't pump a drop right out of the box. It creates suction when working it manually in your hand.

Hard to tell from your pictures of the cam lobe whether it's worn out or not. It does show some wear, but you can't see the top of the lobe (assuming each of the 3 pictures were taken at different camshaft positions.) You'd need to see if the lobe would make an item (screwdriver?) move up and down when cranking the engine over by hand.

Those are just different exposures of the same photo.

Take some more pics with the cam in different positions, with enough lighting so that we can see the top of the cam lobe in each shot.

Easier said than done. I'm actually amazed that these pics came out so well.

I basically just held the phone down there and snapped away. Nothing I can do about lighting. That's all flash.

But does it matter anyway? If the cam is ruined, there's nothing I can do about it because I'm not going to rebuild the engine when I can just install an electric pump.

Is there any other logical explanation for this situation?

There isn't a camshaft lobe like those for a lifter. It's more of slow rise or off center circle (see picture).
The 3 pictures of the cam is showing the back. Cam needs to rotate 180 degrees.

The new rocker arm wear pattern on the new pump looks weird or is that a scratch on the right side?
If that is black paint, I would sand it off and clean it with solvent. Let dry and use a black marking pen and make the arm black.
Reinstall and try to run the engine. Check the wear pattern again.

The wear on the glass bowl pump looks normal to me.

I seem to remember it is possible to install the pump with the arm over the top of the cam lobe instead of under it thus causing the pump not to work. But, I could be wrong, I was once!

Yes, the wear pattern on the Carquest pump is only on the edge of the pump arm rather than all across the face. Very strange.

As for installing the pump with the arm over the cam, that wouldn't explain the first pump working for a year and a half and then quitting suddenly. When installing both pumps I can feel the arm touching the cam.

The wear pattern on the replacement pump may just mean the arm isn't well constructed. That could happen in today's quality control environment.

You could see if the cam lobe (an off center circle like buoymaker said) is worn by comparing the angle of a screwdriver held against the top of the cam and the top of the pump opening in a couple of different positions of the cam. But I have my doubts it would be worn enough to cause the pump to quit working in a short period, and there would likely be a LOT more wear on the arm of the original pump.

So your thought is that the pump that quit working and the new one that was just installed are so poorly made that neither will work at all?

I know what you mean about quality control at the slave labor factories of Red China but I'd expect the new pump to at least pump a little or work for a short time.

Comparing both Carquest pumps to the original glass bowl pump indicates that the pump arms extend slightly different lengths.

The distance from the mating surface of the pump body to the tip of the mating surface of the arm, is as follows.

Glass Bowl Original: 1 7/16"
"Failed" Carquest: 1 17/32"
New Carquest: 1 5/16"

Obviously all three pumps are quite different from each other in how far the tip of the arm extends when relaxed. The new one is shorter by 1/8" compared to the original. The pump that supposedly failed, however, has an arm that extends 3/32" further than the original glass bowl pump. That makes it unlikely that the arm reach is too short to contact the cam properly.

The wear pattern on the "failed" pump looks like it was barely contacting the cam - as if it were riding on the very edge. There's no way the camshaft can move out of position, is there?

I have a new old stock AC 4149 for comparison.
My guess is they used the wrong rocker arm in that problem pump.
Look the gap at the bottom (pivot). There is a lot of the pin showing.

I'll check the pivots on both Carquest pumps along with the glass bowl pump. I'll also check to see if there is any free play side to side.

Interestingly the arm to base measurement of the pump that "failed" is greater than the measurement of your pump so there shouldn't be any problem with the reach of the arm not extending far enough to contact the cam.
The original glass bowl pump is 1.4375" which is slightly less than your pump.

The new pump, which has never seen service, is .1555" less than your pump.

Even if the pump arm isn't aligned exactly center with the cam, it doesn't explain why it worked for over a year and then suddenly stopped working.

The measurement from the center of the mounting holes to the side of the pump arm is 3/4" on all three pumps on both sides of the pump so misalignment of the arm doesn't appear to be the problem.

No significant play of the arm from side to side is noted on any of the pumps.

I did notice that the construction of the the Carquest pumps, the glass bowl pump, and your pump is different enough to make the pivot pin impossible to see in the glass bowl pump. I think the Carquest version is just easier to see the pin com,pared tot he other two, making it look like the arm is off center.

I just installed the glass bowl filter which still produces some suction and pressure when operated by hand.

It filled up with gas but would not squirt any out of the outlet.

Otto

Here's what I'm talking about on how to check the cam lobe. But I don't think you'll find it to be a problem.

What you're describing sounds like an inlet check valve in the pump (both of them - It's not the first time that a part has been bad out of the box) stuck in the open position or leaking enough that it pushes the fuel back into the tank instead of up to the carb.

You can get a repair kit for the original if you want to use it from Then and Now Automotove Link. Fuel pumps aren't that hard to repair. I did that on my original glass bowl pump and they even include the strainer that goes on top in the bowl.

How will I know if the screwdriver is moving the requisite amount? I assume that even if the lobe is worn sufficiently enough to cause the pump not to work properly, it would still have enough eccentricity to seesaw the screwdriver up and down.

I've had crap Airtex fuel pumps fail when practically new for both my '79 Ford pickup and my '56 Cadillac. In the case of the Cadillac, the check valves, which are supposed to be staked at the factory, are not. I took apart a couple of Cadillac pumps and staked the valves in place and they now function perfectly.

It might be the same situation with these pumps but I'd still expect to see a little bit of fuel squirt from the outlet. This also does not explain why the glass bowl pump doesn't squirt out a drop even though it will produce suction when worked manually in your hand.

I'm really hoping the problem is in the pump(s) and not the camshaft but the preponderance of evidence thus far is pointing toward the cam.

I think I will disassemble the Carquest pump that was working and then stopped working and see if the check valves have popped out of their seats.

Here is the Cadillac pump with the valve staked after it jumped out of its seat. I was able to perform the surgery with the pump in situ. The last picture shows what I found when I opened up the pump. Valve laying on the diaphragm.

Here is the inside of the supposedly failed Carquest pump.

Nothing damaged, torn, loose, leaking, or anything. Check valves are solidly in place and work with mouth pressure to open and close.

Also notice how clean it is inside. I didn't wipe it out or clean it at all. Debris clogging up the works can be ruled out.

If it turns out that the cam is not ruined (seeming less and less likely) I would rebuild the original pump. How do I know what kit to use? I don't know the part number of the original pump.

There should be a number stamped on the pump housing (pic shows the number on mine.) Search Then and Now Auto's site for that number and it should come up with the kit you need.

Go to Google.com and enter "[stamped number] site:www.then-now-auto.com" in the search box.

Thanks, it's probably covered up with grime. It all might be a moot point, though, unless someone can give me a reason why none of these pumps work even a little bit if it isn't a worn camshaft.

Has anybody ever had a fuel pump quit because of a worn eccentric? What would be the cause of a sudden failure? There's plenty of oil in the engine and the oil pressure reads 15psi while running and 8 psi at idle which is right in the acceptable range.

If your fuel pump cam was worn off to the point of being ruined, it seems to me that there would be horrible scoring all the way around.
I can't tell from your picture if it shows the high side of that cam. Turn the engine over until the high side shows and take another picture.

Yes, I'll do that tomorrow.