Replaced fuel pump not getting gas

Anything Corvair related
Post Reply
Posts: 5
Joined: Sun May 04, 2014 9:48 am

Replaced fuel pump not getting gas

Unread post by Lola » Sun Oct 08, 2017 6:44 am

We Replace the fuel pump and gas is not getting to the fuel pump what do you think the problem could be

User avatar
Corvair of the Month
Corvair of the Month
Posts: 7606
Joined: Mon Aug 06, 2012 12:33 pm
Location: Lake Chatuge Hayesville, NC

Re: Replaced fuel pump not getting gas

Unread post by bbodie52 » Sun Oct 08, 2017 8:38 am

:dontknow: You did not state what type of fuel pump you installed. Did you replace the original mechanical fuel pump with an identical replacement mechanical fuel pump? Or did you remove the mechanical fuel pump and replace it with electric fuel pump?

Depending on your answer and the circumstances involved with installing the replacement pump, a possible answer depends on a more complete question. So I will dump a long answer that contains several possibilities on you for your consideration…

If you installed an electric fuel pump to replace the original mechanical fuel pump, the physical location for the new electric fuel pump is important. Mechanical fuel pumps are good at drawing fuel long distances from the fuel tank. That is why the original mechanical fuel pump that is mounted on the engine can do a good job of creating a vacuum to pull the fuel the length of the car from the fuel tank to the fuel pump. However, electric fuel pumps typically do a poor job of pulling fuel across long distances. They are much better at pushing fuel than pulling it. For that reason an electric fuel pump should be mounted only a short distance from the fuel tank outlet. It essentially requires a gravity feed from the fuel tank to the electric fuel pump inlet. At that point electric fuel pump can effectively pressurize the fuel outlet to deliver fuel the entire length of the car all the way to the carburetors. So if you installed an electric fuel pump and mounted in the engine compartment it probably is incapable of drawing fuel all the way from the fuel tank. You would need to relocate electric fuel pump to a protected location near the fuel tank so that it can function properly.

However, if you simply replaced the mechanical fuel pump with an identical mechanical fuel pump, there are several possibilities that could be preventing the replacement pump from working properly…
If you believe that the mechanical pump failed 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.

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:


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.

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

User avatar
Posts: 2171
Joined: Sun Apr 18, 2010 2:36 pm
Location: Atlanta, GA

Re: Replaced fuel pump not getting gas

Unread post by terribleted » Sun Oct 08, 2017 9:00 am

Most common causes are fuel pump improperly installed (not pushed down so that the pin in the locking bolt is in the hole in the pump base), plugged fuel line (or fuel strainer sock in the tank) somewhere between the tank and the engine caused by debris or rust in the fuel system, or a hole in one of the 2 rubber connecting lines causing the fuel pump to suck air (one rubber connector at the tank outlet and another located above the left rear wheel between body and engine fuel lines).
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
Currently working full time repairing Corvairs and restoring old cars.

Located in Snellville, Georgia

Posts: 9
Joined: Wed Oct 26, 2016 7:16 pm

Re: Replaced fuel pump not getting gas

Unread post by Gwrodzhi » Mon Oct 09, 2017 6:13 pm

Leave the input line attached and disconnect the output line, loosen the bolt and pump the pump by hand gently and see if it will push out gas. If so then it was installed incorrectly. It's an easy way to eliminate an issue.

User avatar
Trip Rodriguez
Posts: 9
Joined: Sun Oct 08, 2017 10:05 pm

Re: Replaced fuel pump not getting gas

Unread post by Trip Rodriguez » Mon Oct 09, 2017 8:36 pm

I like to pump up a newly installed fuel pump by hand (do CPR on it with the bolt loosened up!) until it's feeding fuel. It often takes a bit. It's very easy to install the pump too high or too low when you tighten the bolt and that will often cause it to not work.

What I do is tighten the bolt with one hand while I move the pump up and down with the other. This way you can feel the bolt go into the hole and know you've got it right. If it's been installed wrong and you pull it out you'll see the spot where the bolt got tightened against the body of the pump above or below the hole. Make sure the bolt is in the hole as described above, then tighten it just snug. Don't torque it up, instead tighten the nut to lock it in place.

As for reasons the new pump didn't work there are only a couple other possibilities. Defective pump, air leak in the line to the tank, or bad pickup in the tank. Also no gas in the tank is always a possibility I guess! There are two pieces of rubber line between the tank and the pump, one just in front of the engine room above and inboard of the left rear wheel, and the other up front near the gas tank. If they are old/questionable, it's best just to replace them.
Ray "Trip" Rodriguez III
Gouldsboro, PA
66 Corsa 140 coupe
65 Corsa 180 coupe
64 Monza Convertible
61 Air conditioned Monza coupe (Missy's car)


Post Reply

Return to “Corvair Talk”