Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks


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#475230 10/17/22 04:09 PM
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Mike Z Offline OP
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While trouble shooting my hard starting, I measured my fuel pump pressure and found it to be nearly 5 pounds. I think it should be between 3 and 4 pounds. Maybe my gauge is a little off. BUT..... after reinstalling my glass bowl sediment bulb, I noticed that it does not fill very fast. So I want to remove it again and try to measure the fuel delivery. Does anyone know how much fuel a pump like this should deliver? Thanks, Mike

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Mike Z #475232 10/17/22 05:11 PM
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It looks like Chevrolet kept that a secret but if you have a later fuel pmmp (made since 1952) the pressure was 4 1/2 pounds.
I looked trouugh 4 different manuals.
Probably a good idea to remove gas cap a gently bolw some air thru the line (from behind the fuel pump)

The Max pressure was increased in mid 1951 from 4 to 4 1/2 pounds. This would include eplacement fuel pumps made after 1952.

Do you need a running board moulding? I have a new one but do not want to ship it......cheap.


Gene Schneider
Mike Z #475234 10/17/22 05:49 PM
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Mike Z Offline OP
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Gene, good to hear from you. I too looked in a bunch of manuals from 1942 to 1951, but no soap. My pump is an original with newer guts in it. I rebuilt it maybe 15-20 years ago. I just did a delivery test and got about 2/3 cup of fuel in 30 seconds. Does that sound OK? I was disappointed in how the fuel came out. I was expecting to see it gush or squirt out of the hose, but it was more of a dribble with air bubbles. Maybe tomorrow I want to check the suction side of the pump and check the fuel line from the tank. Sorry, I have two good mouldings.Thanks, Mike

Mike Z #475235 10/17/22 05:53 PM
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That sounds normal to me.


Gene Schneider
Mike Z #475237 10/17/22 05:55 PM
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Mike Z Offline OP
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OK, I'm still going to check the fuel line and the suction side of the pump. Thanks, Mike

Mike Z #475239 10/17/22 06:12 PM
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If you do some backwards math, you can determine that the fuel pump needs to deliver about 6 ounces a minute if you are driving at 35 mph. So it seems like your pump might be giving you the volume you need. When you say 2/3 cup I assume you mean about 5 or 6 ounces at idle.

I did find a fuel pump test in the 1955 shop manual. That pump should deliver a pint in 45 seconds at 1000 rpm.

The 1949-53 shop manual states that the combination fuel-vacuum pump should deliver 1 pint in 1 minute at idle.


Rusty

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Mike Z #475265 10/18/22 11:56 AM
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Mike Z Offline OP
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That is interesting. I was wondering how you arrived at 6 oz/min. So, I tried to figure it out. If my car gets 15 miles per gallon and is running at 35 miles per hour, the car is using 2.3 gallons of gas per hour (35/15=2.3). A gallon is 128 ounces so the car is using nearly 300 ounces of gas per hour (2.3*128). Divide that buy 60 minutes in an hour and I get 5 ounces of gas per minute. Neat! So since my pump is delivering 5.3 ounces in 30 seconds or 10.6 ounces in a minute, My pump should easily be able to keep up with the demand for fuel the engine is making. I learned something, Thanks a million, Mike

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Mike Z #475266 10/18/22 12:53 PM
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The real tesk for the fuel pump is to supply enough gas to keep the carburetor bowl full at full throttle at top speed. or a steep grade at 60 MPH.


Gene Schneider
Mike Z #475267 10/18/22 01:20 PM
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I agree with Gene about the ultimate test!

I used 14 mpg in my rough calculation. Most of these cars do better than that at 35 mph, maybe more like 17 or 18. My '37 would do about 14 mpg at 55 mph.


Rusty

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Mike Z #475274 10/19/22 05:29 AM
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I've been driving my '40 since 1963 (about 360,000 miles)and have replaced numerous fuel pumps. Being a farm boy I always used the ultimate tests. If you loosen the fitting enough at the carburetor with the engine at idle and fuel squirts, you are good to go. If it dribbles you've got problems. Back when I was running the car hard, fuel pumps lasted 15,000 to 20,000 miles. Gene may pipe in here with his experience. Since I don't drive the car as much now, it seems to me the pumps age nearly as badly with time as they do with use. I have never had a debris problem all of these years. Of course with constant driving, I've always kept fresh fuel.


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My fuel pump problms over the years were mixed.

Had no problems in my every day drivers back in the 1950 and up to 1966
Had a 1966 with a 283 demonstrator(was the parts manager and a new car was furnished) and fuel pump pooped out on a trip. ran OK on the level but died on the hills. Puled into the nearest dealer and was replaced under warranty. I never trusted the new cars back then and got two or three a year,

About 25 years ago my '34 died on the road. I always carried a new fuel pump with me. Installed the new pump and ran well. Later took the bad punp apart and found a little short piece of string caught under one of the the check valves.

Over the years I had a problem with the '39 and 1950. They developed massive oil leaks around the pivot shaft for the lever. In both cases I was returning from far away places (meets) and driving fast on the highway.When I got home and checked the oil the next day I found only a drop on the end of the dip stick,,,,I was lucky.

Fast forward to last Saturday, A friend and I were going to take the "50 out for a ride. When he backed the car out of the garage I saw a clear fluid leaking on the concrete floor. It turned out to be gas shooting out of th bleed hole on the fuel pump. No ride and something to fix next spring.

Especially if one of the cars were not driven a lot for a year or two I would warm them up , take them out on the highway, floor the pedal and run them up to 70 or 80 MPH a few times to see there are any pending weak spots.

Always took many very long high speed tripsand had almost no ptoblems.


Gene Schneider
Chev Nut #475293 10/19/22 05:12 PM
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I have to admit I've never actually "tested" a fuel pump in my life.
But then, I think I've only replaced 3 in over 40 years of farming.

One of them was due to a broken pump spring on a 1976 350 V8.
The engine ran fine but developed a knock that was hard to find.

Second was a Canadian GMC with a 292.
It just quit one day but still had lots of spark and we could hear from the starter that it had lots of compression.
That left fuel, so we swapped pumps and kept on hauling.

Third was a 248 gas powered JD 105 combine.
The pump had to lift the gas a foot with a full tank and more than 2 when near empty.
It wouldn't start after stopping for coffee one hot afternoon.
Got my brother to blow into the gas tank and pressure it up, and it started.
Once running, it ran the rest of the day, but got swapped out the next morning.

PS
Just to clarify the above,
I have of course taken the line off to the carburetor, cranked, and watched for gas.
But I've never used a pressure/vacuum gauge to actually test a pump!

Last edited by Stovblt; 10/19/22 05:21 PM.

Ole S Olson
Chev Nut #475294 10/19/22 06:09 PM
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The broken lever return spring was ver common on 1955 and 1956 models (265). Condensation in the area caused the springs to rust and break.

I have neve tested a fuel pump either


Gene Schneider
Mike Z #475302 10/20/22 12:22 AM
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Great reply Gene and Ole


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