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MG MGB Technical - Fuel Line - Filter to ZS Carb

Can any of you tell me the correct size fuel line from the filter to my Zenith carburator?

I was inspecting fuel lines tonight, and noticed that the PO has a "splice" in the line from the filter to the carb. From the filter there is a larger 2 foot hose, with an adapter pipe that goes from the larger hose to a smaller 4 inch long hose which is attached to the carburator. That 4 inch hose looks like it may have been on the car since 1976 - its cracked and looking bad.

I've parked the car until I can replace it - I can buy 2 foot lengths of hose at the auto parts store, and I could take the hose off and take it with me, but I thought if anyone knew the correct size I could pick one up and do the replacement without disconnecting anything yet.

Thank you!

John
John English

John,

I don't think you should have any problem. Go to the auto parts store and by the hose longer then you need. If it looks like the line is 2 foot long just buy 2 and a half or 3 feet. It does not cost that much per foot and I don't think you have to buy it in increments of feet. If it cost a dollar a foot they should be able to sell you 2 and a half feet for 2.50

As long as you don't have the key turned to the "on" postion you won't have to worry about making the connections on the fly, as the fuel pump will not be pumping fuel. So when you are ready to change the line, start on the carb side. Loosen the clamp and hold a small cup under the connection as you pull the line from the carb. You may get about an ounce or so of fuel that will still into the cup. Now if you can get the cup to stay under the hose go to the fuel filter and loosen the clamp and pull the hose off the fuel filter. You may get another couple of drips from that end but not much to worry about. Now set the cup and the old hose aside. This is a good time to poor the small amount of fuel into your lawn mower gas tank. Now slip the two clamps over the new fuel line hose (which should be longer then you need) and attach one end to the fuel filter and tightened down with the clamp, next route the line over to carb and hold it along side the inlet nipple on the carb. Hold your thumb nail against the hose at the proper length it will need to be and then with a razor knife cut the line to the proper length. Now slip that end of the hose over the carb inlet nipple and tighten the other clamp. Start the car and check for leaks. That should do it.

The only other thing you might want to do prior to hooking the line to the carb side would be to hold a bigger container under the open end and have an assistant turn the key to the "on" position (for a few seconds) just to see how well the pump is working, you should get about a pint of fuel in about 10 to 15 seconds. If the car was running fine before, this last step would not really be necessary and could lead to spilling of fuel.

Save the small left over piece of fuel line that you cut off in case you ever need it in the future. You might need it to replace the line between the tank and the fuel pump or the fuel pump and the solid fuel line (sooner probably more then later). As a matter of fact you should check those areas as well for aging cracked and hardended lines. They probably need attention also. So you might just want to buy 4 feet of fuel line while at the auto parts store.
Hope this helps.
John Fraioli
'79 B
John F

John,

Thank you! I appreciate the detailed directions. It does help, and I can use all the help I can get.

Does anyone know the correct diameter of the hose? Is it an odd size? Moss says that particular hose is NA. Is the correct diameter going to be hard to find?

Thank you.

John
John English

I'd take the hose into the store.

TheMiz

No it is not an odd size diameter and will not be hard to get. I belive it is 1/4 inch inside diameter. But do as The Miz says and just take the old one with with you when you go. Let us know how you make out.
John
John F

Fuel line is 5/16 I.D.
Gary G

A 5/16 ID fuel hose to a Zenith carb is too large for the feed pipe. A 1/4 ID hose should be used. On my setup, there was a 5/16 hose from the fuel filter to an adapter pipe, which dropped the size to the 1/4 hose, which was attached to the carburator. I replaced the hose from the filter to the carb with a 1/4 ID hose - it was a tight fit on the filter, but it works, and now I don't have the adapter in place, which seemed like just another place for a fuel leak, in my opinion.

Thank you all for your reponses!

John
John English

John,
They came with the 5/16 - 1/4 adaptor.
FRM
FR Millmore

Fletcher,

Is there a reason that I should leave it in place?

John
John English

John,
Never could see any reason, except it is much easier to fit the hose, and the small hose doesn't get overstressed, which could eventually lead to cracking. Once the hose gets old, it will be a bear to get off the filter, and may break that. It mostly depends on the stretchability of the line in use, and that decreases with age.
FRM
FR Millmore

This thread was discussed between 28/08/2005 and 02/09/2005

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