72 240z - Problem with mechanical fuel pump?

[SBK86]

Today I took out all the lines around the engine bay, blew compressed air through the fuel lines on the rail and took out the fuel pump again to double check it. I also left the fuel pump attached to the fuel filter and pumped it myself and gas came out the other hose pulling gas from the filter. I put everything back together and poured gas into the hose connected to the carbs and filled them up.

I started the car and I timed it. It ran for about 40 seconds and then cut off. I tried to start it again and got nothing. I then immediately checked the fuel line connected to the carbs and there was nothing in it, completely dry.

Soo.. my guess is that either the fuel pump is too weak or I'm installing the fuel pump incorrectly.

I don't think the carb filter is causing the problem since I can pour gas in through the inlet hose and it runs fine.

I ordered a simple fuel pressure gauge which should be here next week, I checked autozone for one but they wanted 50 bucks.

The fuel pump I installed is an airtex 1080: Airtex 1080 Mechanical Fuel Pump : Amazon.com : Automotive

Anyone else have any experience with this one? Is there a better one anyone recommends?

Also maybe I used the wrong fuel line size and that's causing a problem? I'm using 1/4" ID for incoming which was what the previous owner used.

Edited September 20, 2013 by SBK86

[SteveJ]

Go back to what Pete suggested. Check out the filters AT the carburetors.

[Bonzi Lon]

New fuel pump? hmmmm Is the arm of the fuel pump actually riding on the cam and actuating the pump? You said you pumped it by hand and it worked. Might want to look with the valve cover off see how much it is moving, if at all. Just a thought.

Bonzi Lon

[mayitin]

Air tex seem to be the only one you can get at the stores . they do not last long, the best pump is the original one but but can no longer get the rebuilt kits. the spacer between the head and pump is important make sure is there. for many years I used mechanical pumps and had the same problems just buy a good electric pump and you will never have to worry.

[SBK86]

I think I might have found the problem. I removed the valve cover to get a better look at the fuel pump. It looks like its on the eccentric fine and when I manually pump it, it works. I disconnected the hose by the carb and gas shot out with one pump.

I then reconnected the lines and gave it a couple pumps to fill the line. I heard a pop and gas leaking by the gas can. From all the pressure the return line to the tank came loose and was leaking. I then took a wire coat hanger and fed it through the return pipe on the gas can and it hit a wall and wouldn't go into the tank. The one thing I hadn't checked...

I let a radiator shop that does gas tanks chemically clean and recoat the inside of the tank, maybe they accidentally sealed the return pipe.

So I'm guessing air is getting sucked in from the tank and has no way to escape since the return is blocked which then builds up and won't let gas into the rest of the line.

I'm gonna try shoving the coat hanger in a bit more to see if I can break through whatever is blocking it. I really don't want to drop the tank again.

[SBK86]

I got it running! It survived the short trip to my new house. Thanks for the help everyone

[Patcon]

So was it coating on the inside of the tank causing problems then?

C

[SBK86]

I believe so. I got through some of the coating with the wire hanger and then I hooked everything back up again. I gave the fuel pump a few more pumps with the valve cover off to make sure the lines were all primed. The car didn't start on the first try and I had killed my battery from all the attempts over the last few days so I had to jump start it. It then ran fine.

I did just notice a small drip coming from one of the lines around the gas tank. I'm going to take a break for now and I'll jack it up later and check the lines again. I'm just glad I got it to the new house and I don't have to get it towed at the end of the month .