TBI

[Martin Powlette]

I was hoping to get more discusion on the subject but anyways here is an
update.  I tried Bruce"s test for the IAV and it did not move in or out when in
diagnostic mode ign. on and or off. Fuel pressure ,relay and fuse is ok  I also
noticed that when cranking there was no fuel at the injector.  Almost like the
ECU didn't know the engine was trying to start.   I back probed the TPS and
noticed that the same 5V in was going right back out throttle in idle position
or otherwise, as if it kept on reading full throttle. Toyota has a default
fuction that stops the fuel pump from pumping in wide open throttle when
cranking it also prevents flooding when cranking.   I disconected the TPS and
the hard start was gone, instant fuel at the injector.  I guess the ECU was
substituting the TPS signal.  I will replace the TPS but can someone tell me
what is the exact rtelationship between cranking and TPS reading or have I got
it figured out already.  Thanks for the reply Bruce.

Martin Powlette wrote:

> I saw a mod to the TBI injector on a web page it is a capacitor in paralell
> 0.1 mfd 250V.
> What does it do or solve???
> Someone said the fuel pump relay may be bad and the pump is being driven off
> the oil pressure circuit as a default backup !!!! comment
> Martin
>
> Bruce Plecan wrote:
>
> > -----Original Message-----
> > From: Martin Powlette <marquise at candw.lc>
> > To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
> > Date: Sunday, August 23, 1998 9:06 PM
> > Subject: TBI
> >
> > >I have seen qite a bit of talk on Gm vehicles so I am confident a few of
> > >you guys are familar.  GM TBI V8 5.7 lit I recently did an intake job on
> > >one of those engines and even prior to and now it has a hard start.
> >
> > Freguently, fuel pump starting to go.
> >
> >  The
> > >ignition timing is set at O deg. tdc as the specs recomends but still.
> > >I pulled out the IACV(idle air controll valve ) and though the book says
> > >to wiggle and apply firm pressure to push the pintle the thing is a
> > >bitch just how much is firm pressure????
> >
> > It's a stepper motor, better off to buy a stepper motor controller if
> > you wan to play with it.  ($25ish).   Easy to ruin with too much force.
> >
> >  when I finally got it down I
> > >tried to exercise it back out , my fingers got soar after almost 10 min
> > >of side to side and pull.   Has anyone had that experience.  I connected
> > >the unit whiles out and grounded it on the throttle body, turned the
> > >ignition on and the thing does not buldge, just a slight twitch but no
> > >significant movement whether it was all the way in or out.  Please
> > >advise.  I know the posting is late but I want to get on it tomorrow so
> > >if anyone is out there please help.  Sorrry about the subject matter.
> >
> > Short pins A-B at ALDL and that will extend the IAC.
> > When you trun the key off will retract.
> > Must drive over 40 MPH for IAC to reset, after any of this.
> > >
> > >Martin
> > >
> > >