New fuel tank - pump question

After installing the new tank the other day, I put in about 4 1/2 gallons of gas. No leaks and the fuel gauge is working fine. I do notice that the pump (new SU standard type) seems to be running constantly. I also notice that the connection for the fuel line going into the pump is rather high up on the side of the tank. As it's a non-vented tank, should I fill it all the way up in order to get it pressurized and hopefully stop the pump from running all the time? Is this normal?

BTW, the car runs fine, no hesitation at all.

Thanks,
Bill

Is there any leaks on the fuel line joints to the pump? Are the carb needle valves closing? The other place that an air leak could be is on the suction side of the pump in the tank.

Thanks Jim.

The carbs are new (Jimmy Hilton) and I can't detect any leakage around the pump.

You mention the suction side of the pump in the tank. I'm not sure how to check that. The tank came with a threaded fitting that looked welded into the tank body. I reconnected the metal fuel line from the pump to the tank and it's really tight.

I'll take a closer look.

This may be a method to check for an air leak in the tank. Fill the tank to the top. If the pump now cycles as it should the leak is likely in the tank.
If the pump stops cyling and act up again once the fuel level drops, logic would say the leak is in the tank.
Is the pump sticking in the run mode?

Bill - A constantly running SU fuel pump is an indication of an air leak on the inlet side of the pump. That said, there is one other possibility that can cause the constant runing of a newly installed pump. With no fluid in the pump, the reed valves are dry and will not seal 100%, so it is sometimes necessary to prime the pump to get it operating properly. To check for this condition, remove the fuel line from the carburetors and direct it into a catch container in which you can get the line completely to the bottom of the container - turn the ignition on and see if you are getting any fuel out of the line. If there is fuel coming out and it is full of bubbles, then you have an air leak. If no fuel is coming out, let the pump run for a minute or so and see if it will start pulling fuel through. If it doesn't, you will have to prime the pump. The easiset way I ave found is to have the pump running, remove the filler cap for the tank, get on you knees behind the car and blow into the tank, getting as good a seal between your mouth and the filler tube as possible (close the garage door when doing this or the neighbors may get the wrong impression of you). This will usually get enough fuel to the pump to get the reed valves wet and working as they should. The problem with only 4 gallons of fuel in the tank is that the fuel has to be pulled up to the top of the tank and if the valves are not completely sealing, there is insufficient vacuum being drawn to get it there. Once the fuel has been drawn up to the top of the tank and into the pump you will be fine

If the problem is an air leak, you have at least two joints where the leak can occur, the fitting on the side of the tank and the fitting at the pump. The fitting at the side of the tank is a 1/4" BSP compression fitting and if it is not seated squarely on the portion coming out of the tank, it ill not seal properly. Loosen the nut a bit and wiggle the lne around a bit as you retighten it to insure a good seal. At the pump you may have the wrong sealing washers since it is a new pump. There should be a flat, fiber washer fitted into the grove on the side of the banjo fitting where the bolts seats against it and an 'O' ring in the groove of the port of the fuel pump. I am sending you an article that I wrote (I haven't gotten it into the Library yet) that show the arrangement of the fiber washer and the 'O' ring.
Cheers,

Thanks Dave,

Your suggestions are most welcome. I will check them out.

Unfortunately, I don't have a garage so I may have to wait until after sundown to perform the one, suggestive test. LOL.

Bill

I am not sure what pump you have when you mention SU standard type. I have a new generic type fuel pump and those here advised me that some like mine have a built in regulator and run all the time.

In thinking about the connections to the SU pump, when I installed it (mid-July) I did have to sort of jury-rig the connections both to the pump and the main feed to the carbs (both at the pump fittings).

I suspect this may be the issue if it's sucking air from that point.

Now,.........where is that Moss catalog?

The pump will only suck air on the suction side of the pump. It will spray fuel on the pressure side.

Jim1971 Wrote: