Air in fuel lines and sputtering at high and now low speeds

[zdude1967]

I posted the other day about sputtering at high speeds (100mph) and received some great suggestions. Thanks

There seems to be an issue I just discovered, bubbling in the fuel line, I guess it is air. I orginally thought this to be vapor lock as I am in AZ and it is very hot. However the other day I took the car out and it began running poorly in seconds, well before vapor lock should have occured. I have included a photo it seems there may be air in the line and it is causing bubbles and I guess that is causing an inconsistant fuel flow. I am guessing I have a hole in a line or some loose connection that is causing air to be sucked into the fuel lines. Has anyone had an issue like this, or any suggestions. I do not see fuel line for sale for me to replace the current lines. In any case any insight would be appreciated. I guess this could be why the car begins to sputter as the fuel demand increases at the upper mph level.

Thanks

Glenn

[Bruce Palmer]

If you run all the lines back to the tank and find no wet spots where gas is leaking out and air would be drawn in, then I'd suspect a crack in the pickup tube in the tank.

[Arne]

I have personally seen this issue (sucking air) from loose hose connections on 2 different 240Zs, and have even seen it where there were no wet spots or other external indications. Start by tightening/checking all connections. If that doesn't help, then look into the pickup tube.

[zdude1967]

Thanks. where and what is the pick up tube? sorry for my lack of knowledge. I looked through my manual but did not find anything with that name

Edited September 5, 2011 by zdude1967

[beermanpete]

The pick-up tube is the metal fuel line inside the fuel tank. One end is at the bottom of the tank. The other end comes out the side of the fuel tank near the fuel gauge sending unit. A rubber hose connects this tube to the steel fuel line that runs up to the engine.

The pick-up tube is steel and can rust or crack causing a leak. When the fuel level gets below this leak air is allowed into the fuel line causing reduced fuel flow and poor performance or in severe cases a non-running condition.

[zdude1967]

oh, well funny thing the car stopped running yesterday and I figured it was the fuel pump. I guess the best test would be to add some gas and see if it begins to run again. Is there a way to fix the pick up tube.

Thanks

Glenn

[beermanpete]

A welding shop might be able to remove the old one and weld in a new one.

I replaced mine by eliminating the fuel gauge sender and making a plate to replace it that has a AN bulkhead fitting on it. On the inside I used an 3/8" aluminum tubing bent such that the free end is at the bottom of the tank near the baffle wall. The outside has the usual AN fitting for the flex line to attach. I sealed the original pickup tube with a rubber cap.

[zdude1967]

Thanks everyone, I just have a few more questions based on some recent issues and discoveries.

In my attempt to determine if the pick up tube was clogged or perhaps not working properly I disconnected the line from between the gas tank feed to the metal fuel line. When I did this the fuel ran very freely all over the ground, a lot of fuel. Am I correct in assuming that the pick up tube is working correctly as there does not seem to be any shortage in the flow of fuel from it. From there I disconnected the fuel pump line from the fuel rail and cranked the engine. The fuel flowed in spurts which seemed to be in time with the offset at the end of the cam where the fuel pump -pump lever meets the round thing. I am trying to determine why my car keeps stalling which seems to be getting worse.So does the pick up tube and the fuel pump seem to be working correctly.

Please advise

Thanks

[tetert1]

 I'm having the same problem with my 72 240Z I put clear fuel hoses filter all the way to Su carbs so I can see the bubbles ..runs fine for about 10 minutes gas are in the fuel hoses then  bubbles start to appear from the tank Hardline hose to the filter. So I install electric fuel pump in front of the mechanical fuel, pumped all the gas out of the tank into a container. Gas ran freely there were microscopic bubbles but not large ones. Remove the drain plug on the gas tank no gas came out it was completely empty..  so is  pick up tube good seems like it is?  metal line might be bad ..next I'm going to run a rubber braided fuel line to the mechanical fuel pump from tank. Any suggestions would help.

[siteunseen]

My '72 always had an empty fuel filter while idling.  My floats were way too low and causing fuel starvation.  Since setting them correctly the filter is full.

The easiest and quickest way to get a rough idea is use a clear hose off the float bowl nipple.

This thread got junked up after about the 4th page but there's some good info in there.

 

[tetert1]

 thank you so much for the reply I'm going to check the height of the float and someone said to replace the hose on the bottom of the floats they get old and suck in restricting fuel

[siteunseen]

3 hours ago, tetert1 said:

 thank you so much for the reply I'm going to check the height of the float and someone said to replace the hose on the bottom of the floats they get old and suck in restricting fuel

You are welcome and correct on those hoses. They're still available from your local dealership if you ask them to search by part number, not car.