4ac not getting fuel

[Wedged'86]

Here's a weird problem.
My 4ac isn't sucking fuel through to the pump. it's not enough to fill up the fuel filter (which is new) and it stalls from lack of fuel.
The fuel pump is reletivly new and when i took the hose from the pump to the carbie off it shot fuel like 4 meters so it has plenty of pressure. the problem seems to be before the pump. i've blown all the lines through and a while ago i steamed cleaned the tank and replaced the in tank filter.

Has anyone ever had this or a simalar problem? (why do i always get hit with the cryptic shit?)

Thanks.

[2jzhilux]

fuel tank breather blocked????

[Wedged'86]

which one? the one in the cap? cause if so no.

[love ke70]

run a new line and see if it helps. or just switch it with a different one.
inside of the tube could of delaminated and be blocking flow...
lump of rust or something in there? although,...if you blew them thru...
hrmm

could try getting jerry can. putting short hose from pump onto that, and the hose out the other side of the pump into a container.
if it pumps fuel through its definately something pre pump.
if not you will identify the problem as pump...
if the pump is good, after checking.
drop out tank, remove lines and see whats going on

[Wedged'86]

actually on closer inspection i don't even think there is a breather in the cap.
Where is the fuel tank breather.

i think this might be the answer cause i took the filter out again today and it just kept spitting out fuel like there was pressure in the tank then i got that sucking happening when i tok off the cap.

[oldcorollas]

there should be a tube that runs from the top of the tank, or maybe the filler tube, to the charcoal canister. the charcoal canister should be hooked up to your intake manifold.

[Wedged'86]

Awesome!
Thanks alot dude, if i don't wanna drop out my tank would you recomend just blowing the line through from the charchol canister back to the tank ???

[slapper]

when you disconnected the hose between the pump and the carby and you got your 4m fuel squirt, was that whilst cranking the engine or with everything turned off?

If it was whilst cranking then the fuel pump would appear to be pumping fuel happily.
If it was with everything off, then there's residual pressure in your tank that's splurting the fuel - which is still okay I think ...

okely dokely ... the "if I recall correctly" disclaimer now applies

Everything after 1976 or so should comply with ADR27A which includes a "sealed fuel system" to reduce emission of fuel vapours.

In a nutshell, your fuel cap is sealed and there are two pipes that come from your tank. One goes to the fuel pump (via a filter) and the other goes to a sealed charcoal canister. The other side of the canister is hooked up to a vacuum source - your inlet manifold. As you suck fuel out of your tank, it gets replaced by air sucked in through a checkvalve - either in your filler cap, or in/near the charcoal canister.

You may have the problem where you're sucking fuel from the tank and no air is getting in to replace it ... after a little bit the vacuum in the tank is more than the fuel pump can operate against and you starve for fuel - try removing your fuel cap and see if it runs - if it does, then excessive vacuum in the tank is the problem and you have to look at fixing the check-valve problem.

Hope that helps,
Slapper

[Wedged'86]

The line from the tank to the charcoal canister was blocked. Fixed now runs like a champ.

Thanks guys. Champions.

[love ke70]

thought you said the lines had been blown out

[slapper]

post a quick "how I diagnosed it" .. could be useful to someone in the future doing a search.

cheers,
Slapper

[EldarO]

when you disconnected the hose between the pump and the carby and you got your 4m fuel squirt, was that whilst cranking the engine or with everything turned off?

If it was whilst cranking then the fuel pump would appear to be pumping fuel happily.
If it was with everything off, then there's residual pressure in your tank that's splurting the fuel - which is still okay I think ...

okely dokely ... the "if I recall correctly" disclaimer now applies

Everything after 1976 or so should comply with ADR27A which includes a "sealed fuel system" to reduce emission of fuel vapours.

In a nutshell, your fuel cap is sealed and there are two pipes that come from your tank. One goes to the fuel pump (via a filter) and the other goes to a sealed charcoal canister. The other side of the canister is hooked up to a vacuum source - your inlet manifold. As you suck fuel out of your tank, it gets replaced by air sucked in through a checkvalve - either in your filler cap, or in/near the charcoal canister.

You may have the problem where you're sucking fuel from the tank and no air is getting in to replace it ... after a little bit the vacuum in the tank is more than the fuel pump can operate against and you starve for fuel - try removing your fuel cap and see if it runs - if it does, then excessive vacuum in the tank is the problem and you have to look at fixing the check-valve problem.

Hope that helps,
Slapper

dont wanna be a pain...

but there are 3 pipes..

feed, return, and breather.

Elmo.

[slapper]

but there are 3 pipes..
feed, return, and breather.

Does the carb'd AE86 run a return (I know the EFI will)? I didn't think it did ... although, to be honest, I didn't actually consider the possibility!

I should've taken the time to check my 4AC lumbered AE71 - but I didn't

cheers,
Slapper

[Wedged'86]

it does run a return from the fuel pump.

The way i diagnosed it was when i took off the fuel capit sucked in a lot of air. all that pressure meant it wasn't sucking in air to replace the fuel. Then old corollas told me where the breather line was.

[love ke70]

mine always sucks in air. and runs at about 1600 rpm when you clutch in and back off throttle at the same time when its been under load. god i love it, gives brilliant fuel economy