Starts and immediately dies

[Demerara]

Hi,

I have a 1992 Asuna Sunrunner 5 speed that all of a sudden died. I have compression, spark and fuel pressure. I think I have it narrowed down to a fuel delivery issue. The injector pulses at ignition but does not flow fuel while "running". I swapped the injector out with a known good one and still no continous running, just the initial few seconds after start.

I have read about the ECU and took it out....what a PITA (had to drill the rear screw out after I hooped the head)....but the circuit board looks totally fine. No leaky capacitors or rusted out solder joints. I guess I can't really see inside the caps so they may be toast after all. Is there some other fuse that controls the injector hidden somewhere other than the main box.....I thought I read about that somewhere but can't find the post again?

Is it pretty well assured that I will have to replace the ECU? Against some better judgement I "hot-wired" the injector through a 15 amp fuse and it ran. Not saying I want to keep running that way, but what would the problem be if I did....maybe I shouldn't even be asking.....? I only use this vehicle to move stuff around my property and as a snowplow in winter.

Could it be anything else other than the ECU?


Thanks for the help.

[GeoZilla]

Originally Posted by Demerara

Hi,

I have a 1992 Asuna Sunrunner 5 speed that all of a sudden died. I have compression, spark and fuel pressure. I think I have it narrowed down to a fuel delivery issue. The injector pulses at ignition but does not flow fuel while "running". I swapped the injector out with a known good one and still no continous running, just the initial few seconds after start.

I have read about the ECU and took it out....what a PITA (had to drill the rear screw out after I hooped the head)....but the circuit board looks totally fine. No leaky capacitors or rusted out solder joints. I guess I can't really see inside the caps so they may be toast after all. Is there some other fuse that controls the injector hidden somewhere other than the main box.....I thought I read about that somewhere but can't find the post again?

Is it pretty well assured that I will have to replace the ECU? Against some better judgement I "hot-wired" the injector through a 15 amp fuse and it ran. Not saying I want to keep running that way, but what would the problem be if I did....maybe I shouldn't even be asking.....? I only use this vehicle to move stuff around my property and as a snowplow in winter.

Could it be anything else other than the ECU?


Thanks for the help.

oxygen sensor on the intake?

had mine off (didn't realize it) silly me, kept stalling after a few secodns, but could be something that you overlooked. never know.

[Demerara]

Thanks for the thought geozilla but o2 sensor is hooked up....plus it runs when the injector is hotwired....which should rule out the o2 sensor.

[shackwrrr]

throw the computer back in and follow these instructions

My ECU is bad, now what?

Im sure that he will chime in soon and give personalized instructions for ya buy you might as well start the work.

and oh yea here is some info that you should post up so that jtgh can do what he does best

year
make
model
engine
country
AT/MT
4wd/2wd

[Demerara]

Thanks shack....

For jtgh

1992 Asuna Sunrunner 1.6L 8V, MT, 4WD

Hope to hear back......

[jtgh]

ok , hot wiring the injector invites 2 things
blowing up the other transistor in the ECU or burning up the expensive injector.
don't do that. ok? please , ( i know other hack zuk sites say to do it but they are wrong)

its a 1 ohm injector, (easy has a kiss to blow up with 12vdc , 1 second , gone)
this ECU has 2 transistors for the injector, one grounds the injector and the other applies 12v to the other side
and it is pulse width modulated so it dont overheat.
so you are killiing it.
its your car ,but why do further damage, if you really burn it up more , your core will be rejected, want that?

http://carfix.stufftoread.com/ECU/injector-drivers.jpg

that is the actual schematic of the THis INJECTOR.
uP = MICRO PROCESSOR PORT/
i do not understand this (me dumb)

The injector pulses at ignition but does not flow fuel while "running"

are you saying.
1: car starts then dies and I see it cutting fuel injection , in some way?
2: or ?? not sure...?

you need a NOID lamp. ( 90% effective on 8v due to dual drivers)
only a scope (DSO) is 100% on this car.

so are you saying the NOID flashes while cranking and when it starts , the NOID dies?

yes?
and that at fast foot cant keep it going , on gas pedal ?
then:
the spark feed back is failing. Ignition noise filter bad. (or bad coil)
or the TPS switch is not signaling idle.

if the TPS does not signal idle (shorted switch) then the car will not idle.
the ecu will be clueless what to do , cuz that is an illegal state.

do you need a noid lamp.?

first thing is that the ECU you have is bad.

replace the 2 , injector drivers.Q101 and Q102 .

your country may have diff ID numbers. in your ecu . (we dont have sunrunners here)

[Demerara]

Thanks jtgh

....thanks for the warning about hot wiring...I did it to confirm that the car would run if the injector was feeding the TB as I didn't know if there was some other fuel problem.

I forgot to mention that I also replaced the TPS.

As for

Quote:
The injector pulses at ignition but does not flow fuel while "running"

are you saying.
1: car starts then dies and I see it cutting fuel injection , in some way?
2: or ?? not sure...?

....the answer is the priming pulse definitely happens but as soon as it turns over, no fuel comes out of the injector....I am looking into the TBI. Also if I add a shot of propane it will run for a few seconds. No amount of throttle helps to keep it going. I am gathering here the ECU is telling it to shut down the injector completely. What is the spark feed back? If it is not getting this TPS idle signal, then there is also an ignition problem too?

Okay, so you are saying the ECU is hooped somewhere and I should try replacing the two injector transisitors first and then give it a go........I am no electronics soldering whiz but I may give it a try. I think I can try testing the resistance on my meter following your instructions. I may just end up buying a re-worked ECU if my skills seem challenged if I attempt the desolder/resolder. Got your PN details on the replacements....

Thanks a bunch for this info.

[jtgh]

Originally Posted by Demerara

Thanks jtgh

....thanks for the warning about hot wiring...I did it to confirm that the car would run if the injector was feeding the TB as I didn't know if there was some other fuel problem.

I forgot to mention that I also replaced the TPS. DID YOU CALIBRATE IT?

As for

Quote:
The injector pulses at ignition but does not flow fuel while "running"

are you saying.
1: car starts then dies and I see it cutting fuel injection , in some way?
2: or ?? not sure...?

....the answer is the priming pulse definitely happens , will then ecu is ok.
that proves ECU could in fact open the injector.

but as soon as it turns over, no fuel comes out of the injector....

LOOKING GOOD !
I am looking into the TBI. Also if I add a shot of propane it will run for a few seconds. I bet 2 people on at throttle and other with propane could keep it going, proving sparks is good and timing good.


No amount of throttle helps to keep it going. (good data point, not starving for air trick)

I am gathering here the ECU is telling it to shut down the injector completely.

What is the spark feed back?
http://carfix.stufftoread.com/ECU/91...matic-base.jpg
see brown wire, in the suppressor there is just a 1000 ohm resistor from brown to brown/white, the back EMF from the coil primary bounces back to the ecu
and after starting , the ecu looks here, and if no back EMF then it immediately cancels all injection. (fire safety , collision safety , mandated)

If it is not getting this TPS idle signal, then there is also an ignition problem too? no ,
The TPS must be calibrated as follows or idle fails ,but not starting.
i think a fasts foot will compensate for bad TPS calibration.
TPS testing

Okay, so you are saying the ECU is hooped somewhere and I should try replacing the two injector transisitors first and then give it a go........I am no electronics soldering whiz but I may give it a try. I think I can try testing the resistance on my meter following your instructions. I may just end up buying a re-worked ECU if my skills seem challenged if I attempt the desolder/resolder. Got your PN details on the replacements....

Thanks a bunch for this info.

the transistors are not easy to replace,
and the new ones must be TO-220FP (all plactic no metal type)
getting the correct transistor and removing it is the hardest parts.
TO-220 is packaging style ( a standard)


so you are saying , you key on , see a prime squirt then you crank and dont get squirts.

try this, install the DLC diag jumper , !
now key on, you will see code 12 flash out. (if other come out write them down and post it)
then crank for 5 to 10seconds. (3 is min. so go longer than 3)
now release the key
look at CEL lamp and wait (hope) for code 41 or 42.
DO not release the key , some fail codes are lost at key off.
if you still see code 12, then ecu is happy with spark and with CAS(cmp)
this is buried way deep in the suz docs. arcane stuff.
but very useful to troubleshoot.

Trouble Codes OBD1 Suzuki

41 = weak or no spark
42 = dead CMP or intermittant. (dizzy cam sender )

funny how you get the prime pulse
that pulse is real fast and if that works the ECU drivers should be ok.
that pulse is just to purge any air in the system at key on.

tell me more.

cheers.

[jtgh]

i think another key test is to see how long you can keep motor running with propane.

30 seconds, and spark must be pretty good, as is all else motor wise if it sounds good.


here is my spark page.
this is all it takes to make spark on a bench tester.
Trouble Codes OBD1 Suzuki
see drawing 2, see pin A1 that is the spark feed back pin on mine.
next is my other tester.

the above , circuit is all that is need to make ecu happy enough for spark.
and if its make spark , it wil inject.

that is how you start car coasting down a hell with a dead starter.
dumping the clutch in 2nd hear and she starts and runs.

CMP signals.
Spark feed back,
and it wakes up and injects.

I have scope photos of injector both sides.
and of
this
http://carfix.stufftoread.com/NOID/91-noid-sf1.jpg

injector is unplugged in this photo , 8v motor.
lamp connected in place of injector. cranking here.

a very special low current lamp. see spec there.