260Z several questions/ ideas a lot relating to fuel system

[Zack_532]

I've got a 1974 Datsun 260Z, and quite frankly its been really pissing me off. All of my fuel pump relays are fried, a lot of pieces are missing here and there, so I'm trying to make it run and drive decent on a low budget. My original fuel pump seized up, so Im having to replace that, and my idea was to buy a universal fuel pump and run it direct with a toggle switch. The only problem is having to turn it on and off every time you go to start or stop the car. I've heard about running it through the fuel pressure switch, but I have no idea how to do this, and I can't find any detailed instructions. I also want to make sure its not giving my carbs to much gas. The sensible thing would be a fuel pressure regulator, but I've been told that if they restrict fuel pressure to much you'll burn out your pump. Another issue is my gas tank. Its got the two welded lines in the tank that I don't think come out. The top line you can blow in and suck air out without a problem, however the bottom line is completely clogged, nothing can go in or out. I was wondering if this was maybe some safety mechanism, or if something might be clogging the fuel lines on the inside? I've got the factory service manual, but it doesn't give me a detailed look on the inside, so i have no clue what might be going on there, any help with the second issue would be greatly appreciated. Back to the fuel pump, I was also wondering if I would have to bypass the mechanical fuel pump in the engine cavity in order to use an electrical one, I'm not entirely sure how high the fuel pressure is supposed to be when it gets to the mechanical fuel pump, so I can't judge whether to bypass it or not. Thanks for any help at all.

[Tony D]

"Top Line / Bottom Line" Any sizes? Don't have a tank in front of me to know which end is up. I think a line which is plugged is your first concern. Ram some brazing rod down the line, or maybe a coathanger to see if something is in the bend in the line inside the tank.

 

Get the tank working, after that's done...well...you realize these came with a perfectly good mechanical pump. Since you don't say what carbs you have (maybe the original flat-tops are some of the nebulous 'missing stuff' you refer to...) a mechanical pump may work perfectly fine for you. Since you said 'want to do it on a budget' I'm betting the mechanical pump will work juuuuuust fine.

 

Another advantage of a mechanical pump: They don't burn out when run dry!

[Zack_532]

I need to get out there and see what size lines they are. The top line is the return and the bottom is the feed to the pump. They are twin sidedraft SU's that seem to be in okay working condition.

heres a simple diagram to give an idea of what my lines look like

 

The diagram is if you had pulled the tank out and were facing it the way the tank would have sat when it was in the car. There is also my fuel sender unit on the same side of the tank.

 

o<- This is the top line, which is your return

o<- This is the bottom line, which is my feed, this is the one that is clogged

 

Also I wanted to mention, that when I got the car, it hadn't ran in 15 years, so the mechanical pump was seized up. It just had a lot of trash in it, and I've got it working like new, but I didn't know if it was strong enough to pull a consistent amount of gas up from the tank without the electric one, which came stock on the car. I am on a budget, but I can make room for extras, or neccesities such as a decent pump or new SS fuel lines if its going to save me a lot of time, pain and suffering down the road.

[xShodaimex]

For a car with a carburetor I don't think it is necessary to have an electrical fuel pump. The pressure may be too high for the tank.

[oldhemi]

260Z's came with an electric pump mounted near the gas tank along with an external filter. The electric pump has an internal filter also! It could be plugged. The e-pump is "activated" by the "transistor ignition" box mounted on the passenger side wall. The e-pump is only running when the RPM's are over 400. This is effectively your "shutoff" switch. So, your pump is not on when you are cranking the starter - or if you hit a tree and the engine stops running. BTW, the e-pump was added in 1973 to help solve fuel percolation and vapor lock problems. The flat top carbs were also added for emissions. This info is documented in the FSM.

 

IMO, you do not need the e-pump at this time(trying to get the car to run). TonyD has posted in the past (in response to a question by me) as to a good solution to converting to a JY Ford "safety" rollover-type switch. Do a search on my ID or something because I dont have the info at my present location.

 

Do you still have the original flat top carbs? Just asking to help narrow down some of your problems.

 

A few feet of rubber hose and a fuel tank with a few gallons of gas in it plugged into your mechanical pump would be my recommendation to bypass fuel line and gas tank problems while helping diagnose where your problem might lie. IMO, I would not get SS lines at this time until you have figured out that your lines are fubar. IMO, SS lines are expensive and a little harder to work with, but its your money! Using some air pressure, you could blow out the metal lines and you can judge then whether they need replacing. I have had excellent results doing this with brake lines also. Sometimes I had used miner spirits in the brake lines as a flush.

 

BTW, welcome to the red-headed stepchild 260Z club! My car has been sleeping since late 1991 and I will be going through some of the same things that you will be doing depending on MY health. Both me and me car car are in ruff shape.

Edited June 25, 2010 by oldhemi