Ran out of fuel 260z fuel pump wont bring fuel to carbs

[zdude1967]

Hi,

 

My car was in the garage and I ran it out of fuel starting it to keep the battery charged. This has happened before and is always such a pain in the a** as I usually have to take the whole fuel line apart back to the tank to get the fuel to the carbs. Its like the fuel pump will not pull the fuel once it runs dry (air pocket?) . It does not have the pump by the tank just the one on the engine. In the past I have sucked the fuel into the lines with an extra piece of fuel line and did this to draw it up to the engine. Anybody have an idea why the fuel pump wont draw the fuel from the tank - it now has fuel in it. And / or an easier way to get the fuel to the carbs. HELP!!!

[siteunseen]

Can you pull the hose closest to the fuel rail, stick in a container and crank until fuel comes up? That way it would have nothing blocking the flow to cause any air pockets.

[zdude1967]

It wont do that. It will not bring the fuel unless you get all the air from the line. Any suggestions

[siteunseen]

You mean you can't pull the fuel supply line and from the pump and suck fuel up, like syphoning gas?  If that's the case can you blow back towards the tank and here a bubbling noise?  When I bought a 240 it would run to the end of my street and quit.  I could pull the line off and blow back through it and clear the trash out then it run run long enough to make it back home.  I had a cruddy gas tank.

[Zed Head]

Don't know the ins and outs of the mechanical pumps but shouldn't they hold fuel in they lines when shut down?  Is there an anti-siphon valve, like the electric pumps, either in the lines, at the tank, or at the pump?  I'm suggesting that there shouldn't be air in the lines, you're basically "losing your prime".  Could also be just a weak pump.

Clogged fuel filter comes to mind also.

Edited August 19, 2016 by Zed Head

[Zed Head]

Somewhere out there you might actually be able to get a rebuild kit.  But who rebuilds their fuel pump?  Then you test it.  You can test it first to see how strong it is.

[Patcon]

Shoot a little starter fluid in the carbs and get the engine to turn over. It will pump faster and might prime it. It is very hard to prime the mechanical pump off the starter.

 

Or you could also take the line off on the tank side of the fuel pump and pour fuel down it. It will fill the line to the tank so the pump doesn't have to try to create as much vacuum before it pulls fuel

[Zed Head]

I misread the first post.  Thought he was just having problems getting the car started after sitting.

Even the EFI 280Z's with electric pumps supposedly have problems refilling the lines if the tank runs dry.  

[siteunseen]

You can come up with a way to blow into the fuel fill hole and push it through.  Put your hand over it and stick an air hose blow gun in between your fingers, it'll pressurize it sooner or later.  I think you'd need the fuel rail end open though.

[Mark Maras]

 If the car runs fine when it finally starts, it's probably not crud in the tank. I'd check the pump for pressure and volume flow. IMO the pump is weak.

[Patcon]

 

2 hours ago, Mark Maras said:

IMO the pump is weak

This is possible, but I have also found that the little valves in the pump get gunked up as the fuel turns to varnish from sitting. Sometimes they stick open or closed and sometimes they move but don't seal due to varnish. I have opened them up, cleaned them and reassembled. Be careful not to rip the diaphragm!!! 

One thing to consider is if the car is going to sit for a while undriven go ahead and remove the battery, drain the tank and run the fuel out of the pump and carbs. Our modern oxygenated fuels don't store well

[Mark Maras]

47 minutes ago, Patcon said:

 

This is possible, but I have also found that the little valves in the pump get gunked up as the fuel turns to varnish from sitting. Sometimes they stick open or closed and sometimes they move but don't seal due to varnish. I have opened them up, cleaned them and reassembled. Be careful not to rip the diaphragm!!! 

One thing to consider is if the car is going to sit for a while undriven go ahead and remove the battery, drain the tank and run the fuel out of the pump and carbs. Our modern oxygenated fuels don't store well

 Excellent advice. I've never disassembled one to see what was wrong. It was always, out with the old and in with the new. Odd now that I think about it. I usually tear down my throwaway parts. I love reverse engineering.