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Thread: Bizarre Fuelling problem (bit of a long read, complex problem)

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    Senior Member Sprinter Freak's Avatar
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    Default Bizarre Fuelling problem (bit of a long read, complex problem)


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    Car - 1982 corolla

    motor - 16v 4age bigport

    problem - fuel starve/ leaking fuel/ pumps cavitating

    occurs - Getting fuel starve on hard right hand drifts/corners when hot
    -leaking fuel when hot, but not when cold

    -lumpy uneven idle

    Hey guys,


    So im stumped with this one, its been an ongoing problem for 6 months or so and i can't work it out!

    At the last AE86 drift fest, the fuel starve/surge started happening on tight right hand corners (thought it might have been fuel sloshing away from the pick up/sloshing to one side of the surge tank). The main fuel pump a Bosch 070 which runs after the surge tank was getting pretty loud after a few runs, it sounded like it was sucking up air.

    After drift fest, i changed the 070 pump out for a fresh one thinking that was the problem. But at the next drift day it was still getting the fuel surge under hard right handers with a full tank of fuel. I then decided to change the lift pump to see if that would fix it.
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    So i changed from a VL internal lift pump to an external carby 7psi box pump(changing the in tank pick up to stock uncut one). I also added a one way valve after the box pump so it wouldn't loose pressure, Incase thats what was causing it.



    Then went and did a Wakefeild drift day recently, in the morning it seemed fine. No surging or loud fuel pumps.

    Towards lunchtime it started surging again on right handers, i took it back into the pits. As i pulled up is was pissing fuel out from under the car (near where the new pump was installed) the pumps were both extremely loud as well, sounding like they were working hard.

    I turned it off and let it cool down, the leaks stopped. I had a look over the rubber lines but couldn't see any obvious tears or splits, i did notice that the return line to the tank was a little kinked but, but not massively. I started the car again and the leak had stopped, i then filled the car with petrol incase it was low.

    Took it out for a few more runs, seemed like it was running ok and the pumps were quiet but after 20 minutes it started surging again. Pulled it back into the pits and it was leaking again. I left it for the rest of the day, as i went to put it on the trailer it was hardish to start and there was no leaks it had also developed a very uneven idle, usually it sits just above 1000rpm and idles very constant. It was now sitting just below 1000rpm and bouncing a bit.

    A few days after i tried to start it, again not easy to start. I couldn't get it to idle for the first few seconds, had to keep my foot on the throttle or it would die. It also felt strange, sputtering for a bit as if not getting fuel, then picking back up like it just got a enough.

    Am going to change the plugs today and test how many amps/volts the pumps are getting.

    Other then that what should i be checking/replacing?


    Any help is much appreciated guys, am pretty lost as to what it could be at the moment.

    Cheers

    Ryan

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    sounds like you are running your pumps while they are starved for fuel. This makes them hot and sad. You need a surge tank.

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    I'd start by replacing your fuel hose at the tank. You can do it without dropping the tank. Perhaps it is still carby hose and over time has been stretched by the pressure?

    The efi hose which you can buy from repco. I put 2 efi hose clamps on the stock ke70 lines a few mm apart to ensure a snug fit and have never had issues. Plus the clamps are like $1ea

    I wouldn't be surprised if you are leaking fuel, which in turn is not filling up the pump / making them loud / hot.
    Last edited by Matt; 18th September 2014 at 05:48 PM.
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    Senior Member Sprinter Freak's Avatar
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    Quote Originally Posted by munki View Post
    sounds like you are running your pumps while they are starved for fuel. This makes them hot and sad. You need a surge tank.
    I run a surge tank....

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    Senior Member Sprinter Freak's Avatar
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    Quote Originally Posted by Matt View Post
    I'd start by replacing your fuel hose at the tank. You can do it without dropping the tank. Perhaps it is still carby hose and over time has been stretched by the pressure?

    The efi hose which you can buy from repco. I put 2 efi hose clamps on the stock ke70 lines a few mm apart to ensure a snug fit and have never had issues. Plus the clamps are like $1ea

    I wouldn't be surprised if you are leaking fuel, which in turn is not filling up the pump / making them loud / hot.
    when i replaced the lift pump i used fresh Gates EFI hose and clamps through out

    hmmm i think i need to pull all the lines off and check them thoroughly, possibly pressure test the pump to check the seals aren't faulty.

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    Do u have access to a fuel pressure tester? I'd be measuring that.

    If you are leaking fuel at the tank, tighten the clamps there. Its really the only spot they can leak from.
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

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    Blow the lines out with compressed air too whilst at it. It can dislodge crap causing poor fuel flow
    Ae86 Drivingclub - Toyota AE86 Car Club where AE86 | KE70 | Toyota 86 / GT86 | Subaru BRZ | Scion FRS owners

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    Are you running in-line fuel filters? I've had struggles before with debris from the fuel tank blocking the fuel filter for the lift pump. From the sounds of things your issue is on the lift pump side, thus the surge tank isn't being sufficiently filled and the efi pump is starving.
    You can have any brew you want... as long as it's a Datsun / Corolla / What is that?

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    So is the lift pump plumbed straight into the main pump? or through a surge tank?

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    Quote Originally Posted by Sprinter Freak View Post

    So im stumped with this one, its been an ongoing problem for 6 months or so and i can't work it out!

    At the last AE86 drift fest, the fuel starve/surge started happening on tight right hand corners (thought it might have been fuel sloshing away from the pick up/sloshing to one side of the surge tank). The main fuel pump a Bosch 070 which runs after the surge tank was getting pretty loud after a few runs, it sounded like it was sucking up air.
    Quote Originally Posted by munki View Post
    sounds like you are running your pumps while they are starved for fuel. This makes them hot and sad. You need a surge tank.
    Quote Originally Posted by Sprinter Freak View Post
    I run a surge tank....
    Quote Originally Posted by Jim621 View Post
    So is the lift pump plumbed straight into the main pump? or through a surge tank?
    ITT: nobody who can fucking read.
    You can have any brew you want... as long as it's a Datsun / Corolla / What is that?

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