[Diy_efi] Leaking injectors

[Toyota Supra]

hey bill and brian,

i found a total of 3 leaking injectors, one that i had removed before, and 2 
more in the latest round of testing, all 3 dribbled out, two dribbled out a 
bit more than the others. i was able to swap in two more found and tested 
working, and they held.

as for my test, i took a dsm head, rail and regulator, along with a walboro 
pump. i submerged it into 2 gallons of gas (that was in a bucket) and let it 
run for 20 or 30 minutes. this was able to heat the gasoline up to a 
temperature that was warm to the touch. at this point, i cycled it at stock 
fuel pressure (about 38 pounds with no signal) and up to about 90 psi.

upon that test, i was able to ween out the good and bad injectors. none of 
them seemed to have any physical appearing damage, and suprisingly, two of 
the three that were bad, seemed to hold all pressures after i opened them up 
and let them spray a couple of times, but i still wasn't comfortable with 
reusing them.

lastly, i was able to watch the mechanical fuel pressure gauge and see that 
fuel pressure would hold after the pumps would shut off. before it would 
fall from ~37 to 0 in about 3 seconds following pump shut off ... now it 
will hold for 3 minutes or more.

when the gasoline was heated and at lower pressures, is where the 2 
injectors leaked the most, so thank you both for the suggestions, and also 
to anyone else that has helped me through this crazy situation!

now i have to tune the aic :P

-j






From: Brian Dessent <brian at dessent.net>
>Reply-To: List for general do-it-yourself EFI talk <diy_efi at diy-efi.org>
>To: List for general do-it-yourself EFI talk <diy_efi at diy-efi.org>
>Subject: Re: [Diy_efi] Leaking injectors
>Date: Mon, 27 Jan 2003 16:45:35 -0800
>
>Bill Washington wrote:
> >
> > J
> >     Check the injectors at low fuel pressure, not high - IE the sorts of
> > pressures the injectors will be under when the engine is stopped!
> > High pressure will help to seal them, whereas low pressure relies on
> > their own internal spring tension, this is the worst case scenario, when
> > leaking is most likely to occur.
>
>You might want to also consider heat soak, when a hot engine is stopped
>and left to  stew in its juices so to speak.  I'm pretty sure this is
>the biggest cause of varnishes collecting in the injectors, but I have
>no idea if it effects leakdown.  If a seal is borderline, the higher
>temps might cause it to drip some fuel.
>
>Brian
>
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