[Supras] four cylinder supra

[Christian, Skip]

Khalid,

	Over the weekend, I was able to determine that there's only one cylinder not firing (#4).  Verified compression and ignition are good.   Listened to all injectors with a stethoscope, and all are working and sounded the same.  Guess my next step is to check #4 injector resistance & power.
	Any other suggestions ??  If an injector sounds fine with the car running, is it still possible for it to be bad (in a Supra) ??

Thanks For The Help,  Skip

-----Original Message-----
From: Khalid Almufti [mailto:kalmufti at yahoo.com] 
Sent: Friday, July 25, 2008 0:26
To: Christian, Skip
Cc: berniek at technicaldevelop.com; Supras at supras.com
Subject: Re: [Supras] four cylinder supra

Sikp,
I briefly checked the wiring diagram for the NA and what I see is that the injectors are wired in pairs.  Injectors 1&4, 2&6,3&5 are each shorted together on both sides.  One side is the +12V and the other is the going to the ECU to be switched ON/OFF by a transistor (as Bernie mentioned).  On the ECU, the injector's ON/OFF signals are in the 10 pin dark gray connector.  Pin 8, solid white, is for 3&5; pin 9, white-red, is for 2&6; pin 4, white-blue, is for 1&4.  There is a small connector cover you should be able to slide back (see the service manual on EFI section) that will allow you to access the back of these pins to check voltages.  With ignition switch on, you should see 9-14VDC on all of these pins.  Assuming these transistors are open collector (90% sure they are), then if you don't see voltage at these ECU pins it means the trouble is in that particular pair of injectors.  It could be that the pair is not getting +12V from the  harness.  I doubt it would be open circuit in the injectors, because the two injectors would have to simultaneously go open circuit, which is highly unlikely.  Unfortunately, if you do see 9-14VDC, that doesn't tell everything.  A transistor could be blown and, you'll still see 9-14VDC at these pins, therefore, as Bernie mentioned, you really need to check the switching action of the ECU transistors using a oscilloscope when the engine is running.  But I thought starting there is the easiest first test to do.  Furthermore, if you do get a hold of an oscilloscope, and you do this test first, the pins will be already exposed for checking with the scope probe.
 
Good luck.
 
/Khalid, 90T
 
 
Message: 1
Date: Wed, 23 Jul 2008 18:16:04 -0400
From: "berniek at technicaldevelop.com" <berniek at technicaldevelop.com>
Subject: Re: [Supras] four cylinder supra
To: "Christian, Skip" <wellner.christian at navy.mil>
Cc: Supras at supras.com
Message-ID: <4887ADA4.9000305 at technicaldevelop.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Skip:


Take a look at the wiring diagrams at Cygnus X1 (90 TSRM).  I'll take a look in mine for you if retrieving the information is not possible.  I'm not sure, but I believe the two are connected in some way.  I know that for turbo applications, Toyota's philosophy involved spark retard as shifting took place for the sake of smoothness.  As far as I know, pulling an injector connector off while running should not cause problems.  However, I can tell you that the plastic latches on the connectors will break off as you try to remove the connectors.  My '91 was from Houston (hot) and only had 100K miles on it, and that happened when I disassembled it.  I spliced on other connectors for the 550cc injectors.  The same latch breakage happened with other connectors.  I have a spare '90 turbo harness here but held other connectors on the original harness together with black tie-wraps through both halves longitudinally, going through each wire bundle.  I'd like to get my $400+ back from the new harness, which Jeff Watson will take back, but I have not returned it yet.


BernieK
'91T 5 spd non targa, refreshed JDM, 550 ND injectors, Walbro, 57 trim
CT26 (no clip, wastegate passage bored out) at 17 PSI boost, modified stock FPR, Lexus AFM, Treadstone IC, hardpipes, '98 mounts (strong), '98 wheels and tires, 3" single cat Random Tech downpipe, Lipp, HKS 80 mm
LET-T16 exhaust, Turbonetics recirculated BOV, strut bar, valve bowls deflashed, exh manifold helicoils, lightweight chrome moly flywheel, Exedy organic clutch (street use).



Christian, Skip wrote:
> Bernie,
>
>     Appreciate you taking the time to write the lengthy explanation.
> Hopefully, I'll have time to check out the fuel/ECU system this weekend.
>     I have noticed that there is no smell of fuel from the exhaust, 
> even with the consistent miss.  This would explain, to some degree, 
> the oxygen sensor not killing the engine by forcing it rich, although, 
> there would still be extra air in the exhaust.  Either the above, or 
> the O2 sensor is bad.  Car has 215K miles, and I've never replaced the 
> O2 sensor (no O2 sensor code either).
>     I'm estimating it running on four cylinders, haven't confirmed 
> this yet.  Tried with the ignition, but all checked out fine.
>     Seems like the wiring or ECUs on this car is really failing.  I, 
> also, have an auto trans problem.  The trans acts like the #2 and OD 
> solenoids are bad, but is not consistent.  Half the time, it shifts 
> fine and the other half it goes from 1st to 3rd to 4th to lock-up.  
> But lockup will not hold after 10-15 minutes.  The surprise is when I 
> manually select second gear, sometimes the OD Off light will flash as 
> if its in diagnostic mode, which would indicate there's a trans ECU or 
> wiring problem.  Isn't this car fun.......
>     Are the two ECUs connected, in any way, on the power side ?
> Meaning could a short or open effect both ?
>     Finally, will pulling an injector electrical connector while the 
> engine is running (to see if loss of that injector effects the way the 
> engine is running) cause any other problems ?
>
> Thanks, Skip
>     
>