Replacing ECU

[savage4]

Originally Posted by jtgh

hijack 93 8v: relays TICK when IAC is plugged in.


the IAC electric.
if you unplug it , you must add just a tiny bit of air with your right foot , to compensate.
do not floor gas pedal as that is UNFLOOD mode and kills all injection.
just a little more air.

the coil is 31 ohms, did you messure any of the 2 pins to ground with the meter to be sure the coil is not grounded out.
in must read infinity. (open circuit , just like when leads are not touching any thing)

let me get this clear.
the Fuel pump relay clicks if the IAC is plugged in?
that is correct.?

and always starts , with spray can.
and is tuned up too, fresh ign parts end to end.


the problem is
bad power
or bad ECU.

if you have a load on the ECU on its outputs or on the power lines, this is greatly excessive the ECU will fault.
it takes great car to isolate some faults.
id hate to see you replace ECU and then find a chaffed wire.

IAC pluged in FP-relay clicks.
IAC unpluged All clicks stop.

Spray ---- Starts at once and keeps running, even took a spin around the block.


If I unplug the IAC the pump is not working anymore.
I also mesured the 2 pins to ground, and get no reading, so that should be OK

Just put in :
new spark-plugs
new rotor and distr.
new cabels ,filters etc. so a full tune-up

The distr. and cabels where bad.
Had leaks on the cabels.

I also found SES-switch.
Someone replaced it tot the mountingpoint of the left speaker.
switched it, but the CEL is still on.
It only dimed for a second when I made the switch.

Do I need to ground the ECU when testing, couse up till now I tried it with the ECU just conected, and hanging under the dash.

Btw I found this on the web ( see attachment ).

[Rhinoman]

Originally Posted by savage4

And do I need to ground the ECU when testing, couse up till now I tried it with the ECU just conected, and hanging under the dash.

Btw I found this on the web ( see attachment ).

You can test it without the ECU grounded. I've spent a long time hacking the ECU with just a bare board hanging out of the connectors.
That pdf is a copy from the Suzuki FSM and is very good.
The main power feed is usually a black/blue wire that goes to most of the solenoids and the main relay. Check that you have 12V on it when the IAC is unplugged.

[jtgh]

http://carfix.stufftoread.com/ECU/P&G.JPG

here is the power pins that must not be overloaded. test them carefully ,
some dmm has analog graph to see if the voltage is glitching.
(poor mans scope)

the fuel pump is infamous for that trick, but that is not the only load.

on yours you need to test the coil, done.
and make sure it is not grounded out!

the internal coil can open, or short (not you) and can ground out.
every time the ecu first the IAC (70 times a second) it overloads.
the ecu can not drive a grounded out IAC,
normal IAC current is on the order of 1/2 amps.


The FP relay comes on for 3 seconds,each key on, and every power bump.
ecu might be rebooting do to overload and you hear the FP relay click in.

this is maybe the 25th posting of ECU overload here in 2 years.
the biggest fails rates were.
fuel pump
chaffed wires.
rusted connector on fuse panel.
bad ecu.
you are first with potential IAC ground out.
my mind is open, it can be many things, as this buss connects to many things.
the power buss that is. shown in the schematic i posted.


simplified 8v.. http://carfix.stufftoread.com/Schem-...-1991-jtgh.jpg

ECU b1 and b7 must not be overloaded nor any actuator output line of the ECU.

[savage4]

Originally Posted by jtgh

http://carfix.stufftoread.com/ECU/P&G.JPG

here is the power pins that must not be overloaded. test them carefully ,
some dmm has analog graph to see if the voltage is glitching.
(poor mans scope)

the fuel pump is infamous for that trick, but that is not the only load.

on yours you need to test the coil, done.
and make sure it is not grounded out!

the internal coil can open, or short (not you) and can ground out.
every time the ecu first the IAC (70 times a second) it overloads.
the ecu can not drive a grounded out IAC,
normal IAC current is on the order of 1/2 amps.


The FP relay comes on for 3 seconds,each key on, and every power bump.
ecu might be rebooting do to overload and you hear the FP relay click in.

this is maybe the 25th posting of ECU overload here in 2 years.
the biggest fails rates were.
fuel pump
chaffed wires.
rusted connector on fuse panel.
bad ecu.
you are first with potential IAC ground out.
my mind is open, it can be many things, as this buss connects to many things.
the power buss that is. shown in the schematic i posted.


simplified 8v.. http://carfix.stufftoread.com/Schem-...-1991-jtgh.jpg

ECU b1 and b7 must not be overloaded nor any actuator output line of the ECU.

Hi jtgh,
Its been a long time.
Today I changed the ECU, and all is aok.
thank you for the help.

Have one happy wife, because her baby is on the road again

[jtgh]

great news. !