Do I need an assist fuel pump?

[Stinson]

I don't think being a V12 or V8 engine makes any difference in this situation. The only way I can start my engine after sitting several hours is to add raw gas down the intake to start the engine. This is certainly not a safe or convenient thing to do. It seems that the gas drains back from the glass bowl back to the gas tank. The car runs fine after starting, and will start again easy for a while later, so the fuel pump must be working as designed when driving. But, what is the reason for the gas going back to the tank? I could wear out the battery trying to refill the glass bowl. Do I need to install one of those 6-volt assist pumps as advertised on ebay for about $57 to $67? Or, is there a simple reverse check valve that can be installed inline between the fuel pump and the gas tank?
Thank you,
Ty Stinson
CLC22330

[TJ Hopland]

Check valves are oddly expensive for some reason.  Ebay has them in the $10-25 range but from other places they seem to be in the $50-100 range.    For things like this I used to use the primer bulbs like you would typically find on an outboard motor but apparently due to changes in regulations (or perhaps litigation?) those have got quite expensive too. 

[Steve Passmore]

I use these rubber fuel primmers same as TJ suggests Ty, I have them on all my cars as a very inexpensive way of bringing the fuel up if the cars been sitting 3 or 4 weeks.  You have some other problem if its only a matter of hours. You should still have enough fuel in your float chambers to start, could be a problem in the carbs, chambers draining??

[Stinson]

Hello Steve, good to hear from you. These are new (1940s) updraft replacement carbs. They worked just fine until last June at the time of my son's wedding. Could have developed some sort of leak I guess. I think the use of a marine boat aux tank pump bulb may do the trick as you suggest.
Thanks,
Ty Stinson
CLC22330

[russ austin]

Don't know if your carb has an accelerator pump.  A leaking carb would drain the bowl over time. Fund out why first. It was working before.

[Cooke]

I have just had the same problem with my 38, 60S obviously a V8 but with mechanical pump not a vacuum tank. The glass bowl appears almost empty after a long run on a hot or even warm day after being shut off for a while. The problem is the alcohol in the gas. It’s the heat that boils the gas so it no longer has any or enough in the bowl to start the car. I have a friend that really knows these issues and I think he is correct in saying that an electric fuel pump is really the only way to correct the problem. I have one installed and tried bypassing it (just running on the mechanical pump) only to get stuck with this problem. Once the electric pump is reconnected the problem went away. I also had a 30 Cadillac V8 with an electric pump and never had this problem. By a vane pump, no rubber parts to deteriorate with all the alcohol in the gas. JMHO.

[Stinson]

Hello Mr. Cooke. What is a vane pump (need 6 volts positive ground) and who sells them?
Thank you,
Ty Stinson

[Cooke]

Hi Ty,
This is what I have not called a vane pump in the ad but it is. Rubber mounted to the frame and to the mount,  positive ground is no problem, that is what I have. Hope this helps. I got mine at the local NAPA auto parts store, I assume its available at most large auto part stores. Let me know if you can’t find one. They are made under differant names but they all look like this one.
http://www.speedwaymotors.com/Carter-P4259-6-Volt-Electric-Fuel-Pumps,8837.html



Martin Cooke

[Stinson]

Hello Martin, thank you, where do you have yours mounted - at the gas tank or did you take off the fuel pump and mount it there, or somewhere else? Is the pump always running and is it loud?
Thank you,
Ty Stinson

[gary griffin]

An auxilary pump of any kind should be near the tank. The vaporization temperature of gas goes lower as a vacuum caused by the mechanical pump "sucking" the fuel lowering the vaporization temperature

Simply put "pushing the fuel from the rear prevents vapor lock"

[Bill Ingler #7799]

Here is something to consider when using a vain type pump in line between the tank and the engine mechanical engine pump. The vain type when not running makes the engine fuel pump work harder to pull the fuel from the tank through the vain pump to the engine fuel pump. As Gary pointed out the vacuum suction of the engine fuel pump needed to pull fuel is at a lower pressure so toss in some engine temp and you have low vaporization of fuel which can result in vapor lock. I use a Carter vain type pump but I use a one way check valve so that when the electric pump is off, fuel from the tank goes around the vain pump and through the one way check valve. Very little suction is required to open this check valve. Turn the electric pump on and fuel then goes through the vain pump.

Since I have been using this set up I have had no vapor lock and just use the electric pump after the car has been setting for several days and I always turn the pump on for a few seconds on a start with a hot engine. I have noticed a pump on ebay( see below for ebay listing) which I wonder if anyone is using and how much restriction to drawing fuel through this pump when it is not running? Also below are some pictures of the set up on my 47.    Bill

http://www.ebay.com/itm/6-volt-Fuel-Pump-Cadillac-1946-1947-1948-1949-1950-1951-can-be-assist-or-primary-/151108470351?pt=Vintage_Car_Truck_Parts_Accessories&hash=item232ec4464f&vxp=mtr

[Stinson]

Hello Bill, thank you for this detailed information and the photos. I believe many of us will appreciate you showing this setup. This is exactly what I would like to do then, if I can find the correct check valve as you show. Regarding the 6-volt fuel pump on ebay you directed us to see - that is what got me to thinking about a solution in the first place. So, thanks again to you, Martin, Gary, Steve, Russ, and TJ for a quest well done.
Ty Stinson

[Bill Ingler #7799]

Ty: Here is a parts list and some instructions with prices. This was put together many years ago so prices and parts numbers might have changed. Assembly takes some time to get it right so don`t hurry. The instructions are a PDF file directly below.    Have fun     Bill

[Stinson]

Many thanks Bill. I will take this to the dealers tomorrow. I know a truck fittings supply place to take the list. With your photos even I can now put it together.
Ty Stinson

[Glen]

I think the first thing is to determine if the fuel is draining back or is evaporating.  If it is draining back then you have a problem with your mechanical pump.  The mechanical pump has two check valves that are required to make it work.  If they do not prevent the fuel from draining back then they are defective and the fuel pump is not working as efficiently as it should.  The bad check valves would also explain the hard starting. 


I don’t think there is much difference between putting the aux pump in the back by the fuel tank or under the hood.  I would say that 99%+ of all vapor lock occurs inside the mechanical fuel pump.  The lowest pressure in the fuel system will be inside the fuel pump on the intake stroke.  So as long as the aux pump is pushing fuel into the mechanical pump it very unlikely you will have a vapor lock.  But then you should be sure to not locate the aux pump where it will get hot which in turn will heat the fuel. 

[Stinson]

Hello Glen, thank you. I have an over heating issue with this completely rebuilt V12 engine (new core radiator also). It gets so hot driving 50 MPH (due to high RPM with the original diff) that you can't keep your hand on top of the hood. I have even replaced the fan with two electric fans between the radiator and the engine with a shroud. There were shields installed around the edge of the radiator to the fenders. I don't believe there is air flow sufficient to remove the hot air from the engine area so I will remove them and hope flowing air will help cool the engine.
Ty Stinson

[Glen]

Hi Ty, when ever I hear of an engine overheating at highway speeds my first thought is to check the lower radiator hose.  It should have a wire “spring” (for lack of a better word) inside to keep the suction of the water pump from collapsing it.  It is easy to check, if you can squeeze it closed with normal hand pressure it will collapse restricting the flow of water.   

I have had the wire in the hose rust out and cause that problem.  I took a hanger wire and made a new coil to go in the hose.  Worked great. 

HTH

[Stinson]

Hello Glen, thank you. The single hose at the bottom of the radiator is only about 4 or 6 inches long connected to a metal hose with a very short hose at the water pump end. So, I don't think it is a problem with the hose as you suggest. However, I have noticed that the top two hoses feel like there are air bubbles passing though to the top of the radiator. Don't know if this is normal.
Today, I did not get the parts discussed above. I hope to have all of them purchased by this weekend. 
Ty Stinson

[Glen]

Ty, you should still do the squeeze test.  It is quick, simple and no cost.  The hard part is getting down on the floor and reaching under to get to it.  Didn’t used to be that way 20 years ago. 

If you are getting air you may have a one way leak in the suction side of the pump.  Something to think about. 

[Stinson]

Hello, I purchased the Carter Pump #P4259 from NAPA Auto Parts in Annapolis today for $75.99 plus Maryland tax of $4.55 and no shipping costs. I visited Colliflower, inc. Parker Store today and found that they have the Parker-Hannifin Racor in line check valve for $47.00 but it is not marked as such due to a buyout arrangement with the manufacturer. I was told that I could purchase the Racor from WestMarine. So, I will try to get the exact Racor item from WestMarine but if they don't have it I will purchase the Parker Store brand as it should be the same item. Further, I was told that Baltimore Hydraulics located in Brooklyn, Baltimore should have it. Tomorrow should be the day for finding all the parts required to put the unit together.
Ty Stinson