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Opti-Spark, OBDII, Fuel and you

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Tech scanner things to observe

First..... scan the codes
What error codes is it barking..this might provide another clue.


second clear the codes......
(Dump the battery)

Third..MAKE SURE THE CODES ARE CLEAR.


There is a spec for Injector pulse width
( no pulse duration no flow)

The Hi & Low Rez signals ( See if these move when you crank...no move..no tango)


The HI rez signal should be 360 pulses per crank rev.

The LOW rez signal will be 4 pulses per crank rev.

BUT the combo of the HIGH REZ & THE LOW REZ is what sets the IGN TIMING...
( AND YOU STATE THE CAR RUNS GOOD
< WHEN PRIMED>)!!!!!!! alarm here!

IF A DTC OF 41 is set the ECM will DISABLE the fuel injectors to prevent flooding of the engine~


The other thing you might attempt.... is keep priming the car...

( My fuel pressure gauge has a bleed off line.. I put a little garden sprayer attachment into the end of the bleed hose
(15" long)..

That hose get shoved down the throttle plate and any time I hit the Bleed line I get a little spray of fuel....
Instant (rube goldberg) injection

If it continue's to run.like to warm up.it might be enough to get the OPTI to start behavin...just enough to get it to run on it's own.


I'm still suspisous of the OPTI to ECM wiring..

Vig!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
And a potential TRICK

IF you hold the throttle plate WIDE open on start.. you will fool the computer into thinking
CLEAR FLOOD MODE..( 20:1 as opposed to 14.7:1).. so you MIGHT get injector action then..... Just trying to come up with MORE tricks!


Vig!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Also

I'm still suspicious......

Verify that the injector grounds are ACTUALLY making it to the ECM!!!!!! on the correct pins... ( Will list these later..do not have book @ work)

Something is still bothering me about this.....


Vig!
 
M

Mciamp99

Guest
PINS

I had checked all the grounds at the PCM connectors, some for power, some for ground, I do have a sheet with those locations. They all seemed to be good. As for the open throttle, I treid that once and did get the engine to run for a few seconds, but this was way back in February before the body went back on the frame. It chugged along, but never got to an idle or anything resembling running.

I am off to Carlisle for the weekend so will not get back to it until nextr week a this point.
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Clarification

Not so much the ground's ( EG chassis ground) but the SWITCHED ground for the injectors off the ECM.....

The theory is the following.....

IF the Opti can generate correct spark...it SHOULD be able to calc the injector pulses......

I would hate it to go thru ALL the stuff to replace the OPTI and be in the same place you are now!

Assuming that the engine runs strong..with the OPTI you have...( based on fuel delivery) there is something else hanging up the injectors either error codes causing shut down of the injectors..or a wiring fault....

I now see Chris's logic on switching to a 95 style ECM....

The OTHER thing...is since you are considering replacing the OPTI unit...it might be a cool thing to rip the old one out and open it up to see if it is internally corroded.....

Again more wild thoughts.....


Vig!
 
M

Mciamp99

Guest
I just want to thank everyone who posted to percieved Opti Spark Problem. I want everyone to know tha tI did change the Opti SPark and the problem continued, No Fuel injector Pulse. after going over and over the wiring, we found one wire connected to the wrong terminal at the fuse box.

I am finally so happy to say that our 1975, LT-4 Grand Sport sprung to life on Wednesday November 19, 2002 at 8:05 P.M. I am now the proud papa of a 3000 pound Corvette that was pieced together from 8 other corvettes

Thank you all for your help and I hope to see everyone in Bowling Green in June.
 
M

Mciamp99

Guest
I hope to take some pictures and maybe a short movie sometime in the next week. will let you know when it happens.
 

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