Is my fuel pump failing?

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Bobacuda

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Sorry, but I need some mechanical advice on my late FIL’s 1954 Chevy 150 wagon - all very basic and original.

The fuel system was replaced 3 years ago, including new fuel tank and new Carter mechanical fuel pump. Every thing was working fine, until recently. BTW, non-alcohol gas.

Without warning the fuel pump started overwhelming and flooding the carb - the needle valve and float could not prevent the flooding. At one point it popped a plastic filter housing. I put a pressure regulator on the fuel line to keep the pressure down to 3 lbs. that appears to have helped.

But then it looked like the fuel filter was clogged with “black flakes” about 1/16” in size. Changed the filter… and they were back immediately.

Finally, after the new filter and fuel regulator, the car started losing power and dying like it had vapor lock. Let it cool, add a little gas to the carb, and it would start and run (for a while) again.

Old Chevy guy had me run a “rubber” fuel line away from the engine, under and around the radiator on the cross member and back up to the carb to avoid engine heat (vapor lock). On a very limited test basis this has helped.

So, based on what I have posted, would you suspect the fuel pump is failing, with its diaphragm flaking and its debris moving through messing with the internal check valves?

I’m stumped why the original fuel line route worked fine for 70 yrs, but now it doesn’t.

Sorry it’s a bow-tie, but I appreciate the expertise on this site.

Thanks.
 
I'd start with the source. The fuel tank. Remove it and flush it out and make SURE it's clean. Look at the sock filter on the sending unit ans replace it if needed. Flush all the fuel lines out with compressed air with the line disconnected from the pump. Then disconnect the line to the carburetor and flush it out as well. Pay attention to "what" you blow out of the lines. Lastly, it sounds like it "could" be the fuel pump diaphragm flaking apart. I'd remove the pump and closely inspect it and maybe even tear it down and see if that's the source. If it is replace it, of course.
 
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Generally, except in rare cases, mechanical pumps cannot over-pressure. That is because the return spring is what pumps, the cam that actuates it more kinda "cocks" the pump lever.

DIRT from somewhere, or a problem in the needle/ seat/ float is likely the problem, and dirt is by far more common. What do you have for a filter?
 
New tank, fuel line, pump and filter. The NAPA folks looked up their version of Fram G2 fuel filters. Replaced the one that got split with a new one.

The carb was cleaned and rebuilt, new needle and valve. Later, the carb was replaced with a new Rochester equivalent - no help.
 
Bobacuda said:
New tank, fuel line, pump and filter. The NAPA folks looked up their version of Fram G2 fuel filters. Replaced the one that got split with a new one.

The carb was cleaned and rebuilt, new needle and valve. Later, the carb was replaced with a new Rochester equivalent - no help.
Click to expand...
No it's not "new". It's 3 years old. With the crap fuel supply chain we have now, I would be cleaning everything. It's not like any of it is a hard job.
 
I agree with RRR. Junk in gas, you gotta clean everything! Otherwise, you'll continue to chase your tail.
 
Still chasing. Drained some gas from tank (new 2 years ago),no black flecks.

Online, I did find a person with a similar problem with the same model Carter fuel pump. He said he had the black flecks in the fuel filter and speculated they were from the diaphragm. As it is failing, it developed “Vapor lock” because it was sucking air. He also said his failing mechanical pump did not over pressurize at near idle speeds, but it did at driving speeds or under load. BTW, the fuel pump cannot be opened up for inspection.

Nothing much to lose, I got a new fuel pump I need to install. If that doesn’t fix it…
 
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These are the “black specks” that accumulate in the fuel filter. I cut the filter open to examine and they felt like ground up rubber.
1755908495416.jpeg
 
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Replaced fuel pump. The various parts vendors sell the Carter M2118 for this application. Carter says minimum 3.5 psi, max 5 psi.

It totally overwhelmed the carb. Dug though my stuff and found the pressure gauge - 14 psi. I will put the pressure regulator on tomorrow and test that. :(
 
If you drain the fuel tank, clean out/blow out all fuel lines, replace any rubber lines, take the fuel sending unit out, clean/replace the sock and replace the fuel filter, that should take care of just about any problem short of the carburetor. I would only put about 5 gallons of fuel in the tank. That way, if you have to pull the tank and flush it, it won't have too much gas in it. It is possible that some gunk got in the carb. Good luck.
 
Are you using E fuel? Might not be compatible with the rubber used in the fuel supply system.
 
Only use non-alcohol gas in my old cars, tractor, lawn mower, chain saws, etc.

“Gasohol” has caused me enough grief and loss of time chasing fuel related demons that I only use it in my “new” car or truck that were designed to use it.

Considering where Carter products are currently made, I think it was faulty material day in Mexico or China when the fuel pump was assembled.
 
Barbed fittings sometimes cut the inside of rubber fuel lines causing black flecks creating problems - I opt for the smooth line fittings. My own experience.
 
Put the fuel pressure regulator on, set at 3.5 psi. Tested it with the meter, 4 psi. Well within range. Plumbed in the filter, and so far it’s good. Started right up and did not get overwhelmed by fuel.

Since we are “refurbishing” the car, the interior guy currently has the seat and I am no good at driving sitting on a step stool, so a full test drive has to wait.

Meanwhile, I will search for the rubber hose that connects the tank to the fuel line and the rubber hose that connects the fuel line to the pump.

Thanks to all for input and support.
1755968568220.jpeg
 

Let it sit till late today, and the damn carb was overwhelmed again. Pulling carb tomorrow to check needle valve and float settings.

At least the black speck problem is gone…

I really hate Rochester carbs. Give me a Carter Ball & Ball any day.
 
I have heard of the nitrophyl floats absorbing fuel on TQ carbs & becoming heavy but have not seen one in 50 yrs working on these carbs.
 
Back to my late FIL’s 1954 Chevy wagon and it’s flooding issues.

I have cranked the flow regulator to 1.5 psi, and then I pulled the carb (5th time). I double cleaned every passage with carb cleaner, and if it had any moving part, a small amount of PB Blaster.

The float has two settings - I won’t bore you with how to set it. Anyhow, one setting was dead on, the other directly controls the needle and is supposed to be 1 9/32.”

On my ruler, I must have confused the “16ths” for “32nds.” It was way off. To make the measurement easier, I converted the measurement to millimeters (32.5). Much easier to measure with my ruler.

I’ve run the engine 3 times in my shed for about 10 minutes each time…NO LEAKS! (So far.)
Will check again tomorrow.

Problems resolved - too much psi from the pump and incorrect float settings.
 
Bewy said:
I have heard of the nitrophyl floats absorbing fuel on TQ carbs & becoming heavy but have not seen one in 50 yrs working on these carbs.
Click to expand...
I've seen a few....but none on a Thermoquad. You squeeze them and gas runs out where you squeezed them. When I say a few, I mean maybe three in all the time I've built carburetors. That's a dang while.
 
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