Datsun Roadster Forum-311s.org

I cleaned out the fuel lines by first spraying some carb or parts cleaner in at the engine end, let it sit awhile and blow out with compressed air. It took a few rounds of this but worked great. No need to replaced unless they are rusted out.

I took the tank all the way for a complete cleaning when I started my restoration. I had it dipped in acid and then had a fuel tank liner applied. It should be clean inside. My tank has the baffles inside that it make it impossible to see the complete inside of the tank. There certainly wasn't any loose debris in it when I re-installed it.
I have blown the lines out many times - using my compressor when in the shop and my mouth when I am stranded on the side of the road. You do what you have to do.

I have seen tank fuel pickups clogged with tank liner material. Take something like speedo cable and run down the line into the tank. It was quite frustrating. I was tuning the carbs and then suddenly it would go dead lean. Then a few seconds later it would get way rich. The end of the pickup was down to a tiny hole because of the coating. If your pickup has a screen it would be even worse is it got coated. If you install a T after the fuel pump you can see how much volume the pump is putting out. Run the hose into a can and see how fast it fills up. I think there is a spec for the flow amount.

Could the problem be your gas cap? If the cap is not vented, the mechanical fuel pump may be creating a vacuum in your gas tank when the engine is running.

If blowing through the fuel line gets rid of the problem for a while, this is a clear sign of a clogged pick up in the tank.

Diagnose according to the symptom, not suppositions.

keith0alan wrote:It is amazingly similar to steel brake hard line. Do not replace it with rubber fuel line.

Why not rubber fuel line?

Rubber fuel line shrinks, gets hard, and cracks over time. This causes leaks in odd places when you least expect it. Between the tank and the pump it will suck air in so you don't get gas. BTDT. Rubber line will also burn in two in a fire. Fortunately, I do not have first hand experience with that. The hard line is much more durable and much safer.

I'm gonna revive this thread, because this is exactly what seems to be happening with my 1600. Did you ever find a solution?

Today I took the car out for about 10 min and it was running great. After another 30-45 minute drive immediately after, the car ran like complete garbage 20 minutes into it. Sputtering nonstop, and the temp rose to around 200-220. I parked it, and I haven't checked to see if I lost coolant yet, but for the last couple days I haven't lost a drop with normal operating conditions.

I replaced and fuel pump with a much higher quality one, fuel filters, and ran steel cable through the entire set of hard lines up until the filter where it converts to rubber. I did not replace the rubber, however I am going to tomorrow or possibly tonight if I'm feeling motivated.

Upon further inspection today, I'm having more than ample pressure from the pump to the filter. Next step is replacing the rubber lines to the carbs, and inspect the carbs to make sure they are not having any issues with debris. I've come to the conclusion the hangup must be in the carbs.

Mike

Check the little screens on the carb banjo bolts, and the fuel valves can stick or deteriorate too.
Linda

Gas boils in the bowl when hot enough and will starve the engine
Also if with a vacuum pump hooked to the tank line it doesnt fill the cup up in sec. You have a line or tank problems

I ended up doing a block leak yesterday yesterday showing exhaust in the coolant. So it looks like I’ve identified the root cause of this issue.