Vacuum canister not drwing fuel into it.....

[Profyrfyter]

I'm still having trouble with me 26' DB sedans vacuum canister. I have a new gasket lid gasket, float springs and I've cleaned it all out and now it won't draw fuel into it. I remove the fuel inlet elbow and fill it with gas until the point where I can hear the float click into the up position then I run the car and it will run fine until all the fuel insinde the canister runs out. Before I put the new springs in it would draw fuel in with no problem.

Please help!

Thanks

Dave

[JFranklin]

It must have a vacuum (tight & sealed fittings, screws, and gasket) to draw fuel. The supply line cannot be blocked. the float must be able to rise and fall and the vent must not be restricted, even by an insect nest. Are the springs you replaced of the right value?

[Profyrfyter]

I will tear it down again to make sure everything is free and clear as well as tight. I can hear the float rise and fall with fuel but I'll make sure nothing appears to be binding. The springs were purchased from Myers and are supposed to be the correct ones, but I still have the originals so maybe I'll throw those back in there just to see if it makes a difference.

Thanks for the tips, I'll post back when I finish!

Dave

[72caddy]

When it is running, have you taken off the vacuum line and 'felt' if there is suction? I only ask because it sounds as if your tank is working - it just isn't refilling. Refilling is the job of the vacuum line and the tank/gas line...If it were me I would probably check for clogs/leaks on the vaccum and fuel line first, you may have some old sendiment in the tank blocking the pickup or the pickup is not reaching the fuel level in the tank (my car is a top-draw; not sure about yours)

[Profyrfyter]

Mine is top draw as well. I just pulled all the lines off and cleaned them out with brake cleaner. I also pulled all the fittings off the top of the tank lid and cleaned them out and I was able to wash some brown sediment out of the vacuum port. I put it all back together making sure everything was nice and tight and it seemed to work just fine. I'm still using a 1 gallon jug of gas since the fuel tank still needs to be sealed and I had drawn a line on the outside of it where the fuel level was in the beginning and it dropped approximately 1/2 inch when I finally shut it off so it appears as if the vacuum is working now. It also ran much longer than it had been when it simply consumed the fuel in the canister.

So with that said thank you both for your help!

Dave

[Guest Merchant Xpress]

My fuel pick up on the tank was obstructed and keeping my vacuum tank from working. I found that out when I put an electric pump on the truck and it still wouldn't draw fuel. Now I have it flowing so I may try the vacuum tank again. Now I need to find out why the carb isn't supposed to work with the vacuum tank but will with the electric.

Harry

[72caddy]

Harry,

I suggest creating another topic on this board. A couple of the forum people are really knowledgable about how much line pressure the old carbs can work with and how much will cause more problems than solve.

Profryfytr,

Glad this issue is solved. Sorry you plan on selling it but understand completely...family always comes first. There will be other cars.

[Profyrfyter]

Thanks for the words of encouragement Caddy! Yeah, it's definately not my first choice, but with the way the market is right now we'd be foolish not to take advantage of it. I really wanted to get the vacuum issue fixed before it sells so all someone will have to do is seal the tank and off they go!

Thanks again!

Dave

[Guest Merchant Xpress]

72Caddy, this is a brand new Zenith carb. John the Carb Dr says the new Zenith won't work with the vacuum tank but will with the fuel pump. He hasn't explained why though. I'm guessing it's the low pressure of gravity feed not opening the needle valve. I know with the old carb the electric pump was too much even with the pressure regulator set to 1.5 psi, the lowest setting I could get. I can live with the electric pump if I need to. I think I'll put an indicator light on the dash though so I won't forget to shut it off. I will start a new thread anyway. It may help others having vacuum tank problems and wanting to switch to an electric pump.

Harry

[nearchoclatetown]

Pressure from the pump does not open the needle valve, the float's gravity does. Remember, there's a little spring on the float? When the float sinks, it pulls the valve open. I would like to hear the explanation why that particular carb won't work with a vacuum tank.

[Guest imouttahere]

I remember discussing the issue of fuel pressure on the DB 4-cyl. with Gil Belcher, a Left Coast DB guru who passed away a couple of years ago, at the 1988 DB National Meet in Reno, Nevada. Gil told me that these cars like only about 1 lb. of fuel pressure. Much more than that and the car doesn't run as well. Most fuel pressure regulators that are commonly available aren't very accurate at such a low pressure. That's why, in addition to being correct, a vacuum tank generally works better than an electric fuel pump. I've tried both.

[Guest Merchant Xpress]

I've asked why the vacuum tank won't work with the new carb but I haven't gotten an answer. Maybe the orifice isn't big enough for gravity flow? I'm not sure but the guy who calls himself the carb doctor says the new carb has to be modified to use the vacuum tank.

Harry