Fuel pump not pumping

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saveafrog
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Fuel pump not pumping

Unread post by saveafrog » Wed Sep 20, 2017 4:58 pm

So i have a 1963 corvair and the fuel isnt pumping into the carbs.. I know the pump is good. I bench tested it and it pumped gas but it cant get it to pump when its in the car already.. Any help is much appreciated!

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terribleted
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Re: Fuel pump not pumping

Unread post by terribleted » Wed Sep 20, 2017 5:34 pm

Are the lines clear? Are the needle valves in the carbs stuck closed? Is there fuel available at the fuel line in the engine compartment or is the system blocked up farther forward toward the tank. (try hosing fuel from an external fuel can directly to the pump inlet). Is the fuel pump rod in the engine in place and is it the correct one?
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
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saveafrog
Posts: 4
Joined: Thu Aug 31, 2017 2:28 pm

Re: Fuel pump not pumping

Unread post by saveafrog » Wed Sep 20, 2017 5:44 pm

Lines are clear, i used an electric fuel pump and it pumped the gas that way. I rebuild the carbs and are working great with the electric pump. How would i know if the fuel pump rod is in place and is the correct one?

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saveafrog
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Re: Fuel pump not pumping

Unread post by saveafrog » Wed Sep 20, 2017 6:27 pm


saveafrog wrote:Lines are clear, i used an electric fuel pump and it pumped the gas that way. I rebuild the carbs and are working great with the electric pump. I have to check if the rod is even there.. When i bought the car it didn't even have the fuel pump.

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terribleted wrote:Are the lines clear? Are the needle valves in the carbs stuck closed? Is there fuel available at the fuel line in the engine compartment or is the system blocked up farther forward toward the tank. (try hosing fuel from an external fuel can directly to the pump inlet). Is the fuel pump rod in the engine in place and is it the correct one?
saveafrog wrote:So i have a 1963 corvair and the fuel isnt pumping into the carbs.. I know the pump is good. I bench tested it and it pumped gas but it cant get it to pump when its in the car already.. Any help is much appreciated!

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bbodie52
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Re: Fuel pump not pumping

Unread post by bbodie52 » Wed Sep 20, 2017 6:36 pm

:welcome2: :wave: :wave: Welcome to the Corvair Forum!

If you believe that the mechanical pump is failing for some reason, you should test it to determine the cause of the apparent failure. The pump should be tested for both output pressure and output volume, as described below. There are possible external causes of a mechanical fuel pump failure that can be easily corrected. The mechanical pump itself may also have an internal defect. Proper troubleshooting techniques can identify the fault and possibly validate the need for a replacement pump. Unlike electric fuel pumps, mechanical fuel pumps are good at pulling the fuel the long distance from the fuel tank, and do so by creating a vacuum in the fuel line between the tank and the pump inlet. A leak anywhere in the fuel feed line (between the tank and the mechanical pump inlet) may not be easily noticeable, because that fuel line is not under pressure. But an air leak in the line prevents a vacuum from being formed properly to pull the fuel the length of the car to the pump inlet. This can cause the pump to fail to deliver adequate volume to the carburetors. Procedures for checking for this fault and other potential problems are shown on the shop manual pages below.

If you have any reason to remove and reinstall the fuel pump, be sure that you have installed it properly. You should confirm that the fuel pump is correctly seated and secured. There is a hole in the side of the pump shaft into which the tapered bolt tip must properly seat. If the pump is sitting too high and the bolt is simply pressing against the side of the pump housing, rather than seating inside the tapered hole, the pump push rod will not be doing its job. So first confirm proper pump installation, and then check the fuel pump output pressure and volume, as shown in the shop manual pages below. Fig. 57 in the shop manual page shows the tapered hole that the tip of the bolt fits into. This ensures proper installation and seating of the pump so that the pump mechanism is fully actuated by the push rod.

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bbodie52 wrote:The stock Corvair mechanical fuel pump has proven itself in performance and reliability for decades through millions of Corvairs. There is a tendency to quickly abandon it and go running to an electric fuel pump replacement at the first sign of apparent trouble. Old age can certainly be a drawback or weakness with this pump, but many continue to survive and perform well. There was certainly a history of poor quality aftermarket replacement pumps that developed a bad reputation for a while, and unfortunately rebuild kits are no longer available. But if you begin having what appears to be carburetor problems, don't be too quick to condemn the pump.

There are two relatively simple tests outlined in the Corvair shop manual. These tests measure output pressure and fuel delivery volume. The output pressure test utilizes a common vacuum/pressure gauge that is relatively inexpensive. The output pressure is regulated by an internal spring that is contained in the upper pump housing. Unless your pump springs a leak in one of the diaphragms or seals, it is likely that the output pressure will not change with age. However, new pumps may be fitted with a spring that produces an output pressure well in excess of the 4-5 psi standard. High-pressure can cause carburetor flooding, and is particularly a problem with the Carter YH carburetor found on turbocharged Corvairs, which is sensitive to excessive fuel pressure.

A new fuel pump should always be tested for output pressure. If the pressure is found to be excessive it may be possible to cut the spring or to exchange the spring from the old pump and fit it into the new pump. This may correct the output pressure.

The second test measures fuel flow at the fuel pump outlet. The standard in the shop manual states that the pump should be able to deliver 1 pint of fuel over a period of 40 seconds or less at engine cranking speed. If your pump does not appear to have any leaks and can pass the output pressure test, but fails to deliver the needed fuel volume, the problem may not be with the pump itself. There is a long fuel line that runs the length of the car from the fuel tank to the fuel pump. In order to pressurize and deliver fuel to the carburetors, the pump must be able to create a continuous vacuum in that fuel line to draw the fuel from the tank to the pump. Most of the fuel line is made up of steel tubing and is unlikely to develop a leak. However, there are two short lengths of rubber fuel hose in the fuel path. One section of hose is found at the fuel tank outlet, while the other is found adjacent to the starter motor — just before the line enters the engine compartment. The purpose of the second hose is to absorb vibration from the engine and prevent it from reaching the rigid steel fuel line. If either one of these two hoses develops a leak, the leak itself may not be apparent because the line is not under pressure so fuel will not be forced out. Instead, the leak amounts to a vacuum leak, which can allow air to enter the fuel line. This can prevent fuel from being drawn from the tank to the fuel pump, much like you might experience with a drinking straw if the straw was to split and developed an air leak in the side of the straw. What appears to be a faulty pump that is causing fuel starvation problems in the carburetors often turns out to be a leak in the fuel line at some point between the gas tank and the fuel pump. So if fuel starvation becomes a problem with your carburetors, there is a tendency to question the condition of the needle and seat valve inside the carburetor, or to blame the fuel filter at the carburetor inlet (thinking it is clogged), or to blame the fuel pump itself. Before you blame the pump and toss it, or abandon it and replace it with electric fuel pump, be sure to check the condition of the rubber fuel hoses at each end of the long fuel line between the fuel tank and the fuel pump. You may find that a couple of hose clamps and a few inches of replacement fuel hose is all that necessary to get you back on the road! :doh:

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There is also a fuel tank strainer inside the gas tank on the outlet tube. It was listed as a part used in 1960-1965 Corvairs, but it could be installed on any model year. It is conceivable that this strainer could become plugged and could restrict fuel flow to the fuel pump.
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:chevy:

The link below will provide you with a list of useful websites that are Corvair-related. Some of the links will lead you to an extensive technical library that will allow you to download shop manuals and other technical references in Adobe Reader format at no cost. There is also a link that will help you to locate nearby CORSA (Corvair Society of America) club chapters. While the Corvair Forum can be very helpful as you work on your Corvair, having local friends and contacts in your region who are knowledgeable about the Corvair can also be very helpful. These family-friendly CORSA chapters often offer picnics, group scenic drives, technical training and assistance, car shows, and competition events that can greatly enhance your enjoyment of Corvair ownership. You will also find a list of essential Corvair parts suppliers. Clark's Corvair Parts is the biggest and oldest Corvair supplier in the world. You will find a link that can provide you with a series of videos that amount to a tour of the Clark's Corvair Parts facilities. I think you will be amazed at the quality of the reproduction components they offer — particularly the interior carpeting and re-upholstery items. Parts suppliers such as this truly make our Corvair hobby possible.

Common and Useful Corvair Websites

:link: viewtopic.php?f=225&t=6007

:dontknow: I would like to encourage you to expand on your initial post and tell us more about yourself. If you can describe your personal assessment of your mechanical skills and abilities, that would help a lot. Members of the Corvair Forum love to be helpful in assisting other Corvair owners with technical support and advice, but it helps a lot if we have some understanding of your technical background and mechanical abilities, Corvair-related knowledge, etc. Also, do you have a garage to work in and hand tools, jack stands and a floor jack, etc. to support a restoration project? Helping us to know more about you will help us to write comments to you that are tailored to your needs and experience. Knowing your location is also useful, because knowing where you live can sometimes suggest possibilities.

:welcome:
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

saveafrog
Posts: 4
Joined: Thu Aug 31, 2017 2:28 pm

Re: Fuel pump not pumping

Unread post by saveafrog » Thu Sep 21, 2017 3:43 pm

Awesome i took the fuel pump push rod out and cleaned and lubricated it, and bam! Fuel pump started working. Thanks for the help!

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