The saga continues - carb overflow

[rdefabri]

I just replaced my fuel pump with an OEM model from AutoZone (Airtex). Car started great, until I noticed fuel coming out of the overflow vents at the air cleaner base.

The car ran fine prior to the fuel pump replacement. All that I changed was the fuel pump...I am guessing that this is related to the floats - possible they are stuck (since the car was "dry"). I need to open them up and check.

Assuming that ISN'T the problem - any other ideas? I know the fuel rail is clear, but it's worth checking the return line.

I am bummed

[doradox]

Tap on the side of the carb float bowls. That can unstick the floats if that's the problem. There's also a chance that something got in the fuel line to the carbs when you replaced the pump. But both at the same time? Is it both carbs doing it? Could be too much fuel pressure but that would be rather odd.

Steve

[240ZX]

Your needle and seats my be worn and passing fuel.

[whamo]

One of your fuel inlet valves are stuck open. You should remove the air cleaner to determine which carb the fuel is coming from. Its unlikely both are stuck. It shouldnt require replacement of the valve, just cleaning debris from it. However it may be worn beyond the point of cleaning, in which case replacement will be nessesary.

Edited August 15, 2008 by whamo

[westpak]

floats stuck?

[rdefabri]

All:

Both seem to be doing it, but the rear carb more than the front. I have a feeling the floats are stuck.

If it's the needle and seats, I'd be shocked. The car ran with no issue a few weeks ago, so I don't think that would be it.

Tomorrow I'll open the bowl to see if floats are stuck. Otherwise, I'll try the other suggestions.

[whamo]

All:

Both seem to be doing it, but the rear carb more than the front. I have a feeling the floats are stuck.

If it's the needle and seats, I'd be shocked. The car ran with no issue a few weeks ago, so I don't think that would be it.

Tomorrow I'll open the bowl to see if floats are stuck. Otherwise, I'll try the other suggestions.

The floats actuate the needle and seats, also called fuel inlet valves. They can easily become stuck open by debris in the fuel.

[Force Fed]

Just rap the sides of the bowls w/ a screwdriver handle or old ratchet or something. If they are just stuck, that should loosen them.

[ajmcforester]

When I bought my first Z I found out that one of the vent hoses leaked, so the guy left the tank really low, also the fuel pump was worn and was not pumping at compassity. So got a OEM Kyosan (SP?) pump. then the gas came out like you discribed. So I replaced the seals in the carbs since the car was not well maintained under the hood (needed to be done besides the problem at hand), still had the problem. The next thing I did was blow with my mouth air threw the return line that was hard to do so I pulled the line. What happened is all the air in the fuel tank aided in the return line to start varnishing and collecting rust that jammed in the line. What I did was use pipe cleaner and wire to clean most of the rust partials. Then soaked the line in fuel treatment to break down the varnished gas and cleaned it again with pipe cleaner until a new piece of pipe cleaner came out clean. Also if the line is not clean check the main fuel lines, the vent tank and the gas tank, you may want to have them boiled out to remove any rust. If you know a radiator shop that still boils radiators they can also do your tanks

[rdefabri]

I figured it out - apparently, the arms that secure the floats were bent, possibly when I put them back in the last time.

As a result, the float wasn't closing the valve in the bowl. Hence, there would be no stoppage of fuel flow as the float rose in the bowl...I simply bent the float / float arms back into position and I was good to go...

[Bruce Palmer]

One other thing to do is check the pressure being put out by your new pump. About 3 1/2# is all the needle and seat will stand before being overpowered and held open resulting in an overflow situation.

[rdefabri]

I originally thought that was the problem until I saw the bent float. However, it seems that my original float was flowing poorly before failure - the car had a difficult time starting. Now, the new pump, I start with no problem - barely even need to choke, so I assumed the flow was pretty healthy.

Seeing how much gas pooled (and stained!) my driveway, fair to say the new pump is working well!