No fuel

[Gabenitez49]

Hi everyone I got my first corvair a few months ago and it’s pretty straight, anyway I’m new here so I guess this is a nice way to introduce myself. So I tried firing the 62’ and noticed I wasn’t getting gas to the carbs then I went down to the fuel filter and noticed there no gas getting there either. I went all the way up to the fuel tank and found a very old and brittle hose connecting the fuel tank to fuel line and changed it out in hopes that maybe that hose was just blocking things up and decide to just change the whole fuel line now that I have everything replaced I’m still not getting fuel. I’ve shot air through the line and I can hear and smell it coming into the tank. Could it be the pump? Because I sucked gas before the pump and it came through (I know sucking up gas is bad but I didn’t have a vacuum pump to suck it out). Do I need to replace the tank? Any advice helps thanks


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[vairguy63]

Hi everyone I got my first corvair a few months ago and it’s pretty straight, anyway I’m new here so I guess this is a nice way to introduce myself. So I tried firing the 62’ and noticed I wasn’t getting gas to the carbs then I went down to the fuel filter and noticed there no gas getting there either. I went all the way up to the fuel tank and found a very old and brittle hose connecting the fuel tank to fuel line and changed it out in hopes that maybe that hose was just blocking things up and decide to just change the whole fuel line now that I have everything replaced I’m still not getting fuel. I’ve shot air through the line and I can hear and smell it coming into the tank. Could it be the pump? Because I sucked gas before the pump and it came through (I know sucking up gas is bad but I didn’t have a vacuum pump to suck it out). Do I need to replace the tank? Any advice helps thanks


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Welcome Gabenitez49! Glad to hear you’re getting into Corvairs!! They’re great but a few little tips to try/know about the fuel pumps...

There are many others here with more knowledge but I’ll share what I know from fixing similar issues.

First, they can and do go bad. The are a diaphragm type that can rupture- especially after many years or long times of non operation. The big issue here is that if the lower diaphragm goes bad it will allow fuel to drain directly into the case mixing in with the oil, which is very destructive.

First thing to check is your oil. Pull the dipstick and smell the oil. If it smells like gas you know that’s the issue and will have to take steps to remove all the oil/gas from your case, filter and oil cooler. If it doesn’t smell of gas go to the next step.

Loosen the 9/16” lock nut below the pump and then the ½” set screw enough so you can slide the pump up and down in its bore. Then loosen one of the carb fuel lines from the tee (I usually do the right side line) and remove it from the tee. Then you can gently pump the fuel pump manually to prime it. Put a rag under the exposed tee as gas will squirt out of it once it’s primed. You should hear a squishing sound as you press down and then release the pump if it’s working.

If this doesn’t work you may have a defective pump but the lower diaphragm is still ok. They’re not expensive to replace, about $60, but get one from a Corvair vendor like Clark’s or California Corvairs if you’re in the west US.

I’ve had them go bad and now I just replace them every 4 years max even if showing no signs of problems. Hope this helps diagnose. Best


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[bbodie52]

Welcome to the Corvair Forum!

This information may help to clarify fuel pump troubleshooting possibilities....

When some mechanical pumps aren't pumpin', the pump itself may not be bad. Check the two short fuel hoses in the line between the tank and the engine compartment. They sometimes deteriorate and develop a leak or crack that allows air to enter and makes it impossible for the pump to develop the vacuum needed to draw fuel from the tank to the pump. Some new short hoses and clamps may be all that is needed!

HAVE YOU EVER TRIED TO DRINK THROUGH A STRAW THAT HAS A SMALL SPLIT OR CRACK IN ITS SIDE??? IT CAN'T BE DONE!

The filter inside the fuel tank can also deteriorate and may be clogged...





Strainer Sock, Fuel Sending Unit, 1954-88 GM, 5/16"
https://ssl.corvair.com/user-cgi/catalo ... ow_page=69
Part number C261: 60-65 GAS TANK STRAINER (FITS 60-69)


There are a number of things that can go wrong between the fuel tank and the carburetors that can prevent your mechanical fuel pump from working. You have discovered one of them with your missing pump push rod. The material below will also cover the other possibilities. I've posted a somewhat lengthy fuel pump technical piece that hopefully will give you a good idea of how the system functions — and how to effectively troubleshoot the fuel system.

Fuel Pumps

We have only been able to locate 2 manufacturers of original style Corvair fuel pumps. Since 1973, we have consistently seen 1-2% of new fuel pumps fail. From about 1998-2001, the failure rate went to nearly 10%! We finally convinced the pump manufacturer that they were using the wrong diaphragm material! Currently, about 1%-2% of the fuel pumps continue to have problems. The problems have usually been seepage of fuel or complete failure resulting in no fuel or a rupture of the main diaphragm. The main supplier (C3403) is now using "antiwicking" diaphragms & has returned to all 3 diaphragms having fabric reinforced material. We've also added a pump from a 2nd supplier (C3403A). Our experience with both is nearly identical. A spare pump is always a good idea.

https://ssl.corvair.com/user-cgi/catalo ... ow_page=65

If your original mechanical fuel pump has actually failed (as in leaking fuel, torn pump diaphragm, etc.) the safe bet may be to install an electric fuel pump system properly and abandon the mechanical pump system, if it has failed! (Remember that a leaky fuel tank feed line or hose that is letting air in may look very much like a failed mechanical pump. But if the line between the tank and the pump is letting air in, it is like trying to sip a drink from a cup through a drinking straw that has a split in the side of the straw — you won't get much fluid no matter how hard you suck on the straw! You need a new straw!)

The other common mechanical fuel pump mistake is to improperly insert the pump at the wrong depth, with only the set screw (bolt) pressing against the side of the pump, instead of the tapered bolt tip being seated in the tapered hole in the side of the pump shaft. This can result in the pump mechanism barely making contact with the push rod that drives it. The pump only gets a partial push and never moves at a full stroke. The pump must me inserted fully, with the bolt properly seated into the tapered pump hole and the lock nut securing the bolt as shown and described in the shop manual).

I'll bet a lot of fully functional Corvair mechanical fuel pumps get targeted as having failed and then get tossed and replaced with an electric pump, when the real problem is a faulty feed line from the fuel tank or an improperly inserted fuel pump!

The cost of a replacement mechanical pump from Clark's isn't really that high ($65.55 vs. $69.50 for a Facet FEP42SV Cube Electric Fuel Pump 1.5-4 Psi, Includes Clamps/Fittings/Filter). Other electric pumps may be cheaper, but when you add the additional wiring and install hardware cost — including the safety cutoff switch system — the electric pump system will likely cost much more.

Part number C3403: NON-GM FUEL PUMP-62-69 WILL FIT 60-61 IF ORDER C259 ROD

Weight: 2 lbs 4 oz
Catalog Page(s): 65
Price:
1 - 1 $ 65.55
2+ $ 63.60

The Corvair mechanical fuel pump is usually pretty good at pulling gasoline the length of the vehicle to prime the fuel pump so that gasoline can be pressurized to fill the carburetor float bowls. But a small air leak or crack in one of the short rubber hoses at either end of the fuel line between the tank and the pump can create what amounts to a vacuum leak in the fuel feed line that supplies the pump. The pump can cycle many times as the engine cranks and the battery drains while sucking mostly air from a fuel line air leak instead of getting a good "drink" of gasoline from the tank.

An improperly inserted mechanical fuel pump may also limit the motion of the pump diaphragm, if the pump insertion is too shallow and not allowing the push rod to take a full stroke. Refer to the notes and illustrations below to see how the pump set screw is supposed to insert into the tapered hole in the side of the pump shaft, and not just push against the side of the pump shaft. Proper installation ensures that the pump is properly positioned in relation to the push rod, so that the pump gets a full stroke with each rotation of the crankshaft. Good fuel volume from the pump is considered to be 1 pint of fuel in 40 seconds or less at cranking speed.

To check for the possibility of fuel starvation, you should measure fuel pump pressure AND volume! It is easy to have a pump that delivers correct pressure, but cannot produce adequate fuel volume. A feed line leak or cracked/damaged/loose rubber hose between the tank and the pump can create an air leak that will keep the pump from being able to create a solid vacuum to pull a good supply of fuel from the tank. Without adequate fuel supply, the pump can generate adequate fuel pressure to the carburetors, but only until it is starved for gasoline from the tank. The pump must also be installed to the proper depth and anchored properly using the tapered bolt that is screwed into the tapered hole on the side of the pump.


http://www.corvair.com/user-cgi/catalog ... nd_page=65

Part number C259: 62-69 FUEL PUMP ROD-REPRO (3 13/16") 60-61 ROD=C7256

Weight: 0 lbs 4 oz
Catalog Page(s): 11(28),65
Price: $ 19.15

Part number C1604: FUEL PUMP SPRING

Weight: 0 lbs 2 oz
Catalog Page(s): 11(34),65
Price: $ 3.55

The pump push rod is driven by a cam lobe on the crankshaft. The repeated "upstroke" causes the pump to form a vacuum in the feed line from the fuel source (tank or gas can). As the fuel is drawn into the pump chamber, the one-way valve in the pump inlet closes at the top of the stroke, and the spring in the pump forces the diaphragm back down to push the fuel out of the pump through the other one-way valve, toward the carburetors. The spring tension determines the fuel pump outlet pressure.

Check to make sure you are fully inserting the pump so that the pushrod driving the pump gets a full stroke to drive the fuel pump. Proper installation of the new parts is critical,,,



Also...



For a quick check on fuel availability in the carburetors, you can peer down the throat of each carburetor while holding the choke open. Open the throttle quickly. You should see a squirt of fuel injected into the carburetor throat from the accelerator pump. This confirms the presence of fuel in each float bowl.

With the air cleaner assembly removed, when holding the choke open and peering down the throat of each carburetor, do you see a squirt of fuel from the accelerator pump in each carburetor when you open the throttle rapidly? If the jet of fuel is not observed, the float bowls may be dry, possibly due to stuck needle and seat assemblies blocking the fuel inlet.

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[joelsplace]

Manually fill the carburetors through the vents. The pump may just be having trouble priming so hopefully the engine will run long enough with filled carburetors to start it pumping.